JP4881033B2 - Neutron detector lifetime determination apparatus, lifetime determination method thereof, and reactor core monitoring apparatus - Google Patents

Description

  The present invention relates to a neutron detector lifetime determination technique, and more particularly to a neutron detector lifetime determination apparatus that performs lifetime determination based on an output history of a neutron detector, a lifetime determination method thereof, and a reactor core monitoring apparatus.

  There is a close relationship between the power of the reactor and the neutron flux in the core of the reactor. Therefore, it is important to measure the neutron flux in the reactor core in nuclear reactor instrumentation related to reactor power. In order to measure the neutron flux in the core, a neutron detector is inserted in the core of the reactor. A plurality of neutron detectors are inserted in a radial direction and a height direction of a generally cylindrical reactor core, and are used for measuring the neutron flux distribution in the core and for monitoring the reactor power.

  As a neutron detector for measuring the neutron flux in the core, a neutron detector utilizing fission, such as a small fission ionization chamber, is widely used in a light water moderation reactor such as a boiling water reactor. In general, a neutron detector using fission has a structure in which a pair of electrodes that are spaced apart from each other and electrically insulated, for example, a neutron sensitive substance such as uranium-235 and an ionized gas are contained in an airtight container. Have.

  The neutron sensitive material in the neutron detector using fission is induced to undergo fission by neutrons incident on the neutron detector to produce a fission product. This fission product ionizes the ionized gas in proportion to the neutron flux in the neutron detector. Therefore, when a DC voltage is applied between the electrodes in the neutron detector, the neutron detector outputs a current proportional to the neutron flux in the neutron detector.

  Neutron detectors have a lifetime (usable period). The cause can be roughly divided into the following two.

  The first cause is exhaustion of neutron sensitive materials.

  The neutron sensitive material in the neutron detector using fission is consumed by combustion according to the integrated amount of neutron flux irradiated to the neutron detector. For this reason, the magnitude | size (henceforth a neutron sensitivity) of the neutron detector output with respect to the neutron flux in a neutron detector falls. As a result, the lifetime of the neutron detector (hereinafter referred to as the nuclear lifetime) is exhausted.

  The second cause is deterioration of the structural material of the neutron detector.

  Due to the neutron flux, the structural material of the neutron detector, particularly the welded portion, is deteriorated, and the airtightness of the neutron detector is deteriorated. As a result, the lifetime of the neutron detector (hereinafter referred to as the structural lifetime) is exhausted.

  In order to reliably replace the neutron detector with a new one before the nuclear lifetime or the structural lifetime of the neutron detector is exhausted, it is important to appropriately determine the lifetime of the neutron detector.

  The nuclear lifetime of neutron detectors comes from the consumption of neutron sensitive material by neutron flux. Therefore, in order to determine the nuclear lifetime, it is important to accurately evaluate the neutron-derived component (hereinafter referred to as neutron component) in the neutron detector output that is proportional to the neutron flux in the neutron detector. .

  In evaluating the neutron component in the neutron detector output, the following two points are significant problems.

  The first problem is the effect of gamma rays in the core on the neutron detector output.

  Gamma rays, like neutrons, ionize ionized gases in neutron detectors. For this reason, gamma rays also provide an output proportional to the gamma ray flux in the neutron detector. As a result, not only the neutron component but also a gamma ray-derived component (hereinafter referred to as a gamma ray component) proportional to the gamma ray flux in the neutron detector is always mixed in the output of the neutron detector. This gamma ray component makes it difficult to evaluate the neutron component in the neutron detector output.

  The second problem is the tightness of the neutron detector.

  For example, when the airtightness of the neutron detector is impaired as a result of damage to the sealing portion between the neutron detector and the connection cable, the gas component or gas pressure in the neutron detector changes due to gas leak. When the gas component or gas pressure in the neutron detector changes, the electron mobility of the gas in the neutron detector changes, and the neutron sensitivity of the neutron detector changes. Therefore, when the airtightness of the neutron detector is impaired, the neutron component in the neutron detector output changes.

  The neutron detector output can be separated into an average value of the neutron detector output (hereinafter referred to as a direct current component) and a square average value of temporal fluctuations of the neutron detector output (hereinafter referred to as a fluctuation component). This is because the reaction between the neutron and the neutron sensitive material occurs randomly and has a component of statistical fluctuation.

  In general, neutron detectors are designed so that the fluctuation component derived from neutrons is much larger than the fluctuation component derived from gamma rays. For this reason, the fluctuation component of the neutron detector output has the property of being less susceptible to gamma rays than the DC component of the neutron detector output.

  Conventionally, a technique for monitoring the neutron detector output utilizing the nature of this kind of fluctuation component of the neutron detector output, which is less susceptible to the influence of gamma rays, is disclosed in Japanese Patent Laid-Open No. 4-181872 (Patent Document 1). JP-A-58-100767 (Patent Document 2), JP-A-59-9594 (Patent Document 3) and JP-A-61-59280 (Patent Document 4).

  The method for monitoring a neutron detector described in JP-A-4-218792 (Patent Document 1) is a method for monitoring a neutron detector by using a ratio of a DC component and a fluctuation component of the neutron detector output. . In this method, it is assumed that the intensity of neutron flux and gamma rays irradiated to the neutron detector hardly change. When the ratio of the direct current component to the fluctuation component is below the reference value, it is determined that the nuclear lifetime of the neutron detector has been exhausted. When the ratio between the DC component and the fluctuation component changes abruptly, it is determined that a gas leak has occurred, and the DC component and the fluctuation component affected by the gas leak are used as the ratio of the DC component and the fluctuation component. Have been corrected.

  The lifetime evaluation apparatus for a neutron detector described in Japanese Patent Application Laid-Open No. 58-1000076 (Patent Document 2) uses a DC component and a fluctuation component of a neutron detector output to convert a DC component into a neutron component and a gamma ray. An arithmetic unit that calculates the component separately is provided. The characteristic value of the neutron detector necessary for this separation is measured after the neutron detector is manufactured. Also, the ratio of the gamma ray component to the total output is obtained by this calculator, and if this ratio is 1/6 or more, it is determined that the nuclear lifetime has been exhausted.

  The radiation monitoring apparatus described in Japanese Patent Application Laid-Open No. 59-9594 (Patent Document 3) separates a direct current component into a neutron component and a gamma ray component using the direct current component and the fluctuation component of the neutron detector output. And a microcomputer for calculation. The characteristic value of the neutron detector necessary for this separation is measured after the neutron detector is manufactured. The microcomputer uses the neutron sensitivity and gamma ray sensitivity of the neutron detector as known constants to calculate the neutron flux and gamma ray flux in the neutron detector.

The neutron measurement apparatus described in Japanese Patent Application Laid-Open No. 61-59280 (Patent Document 4) separates a direct current component into a neutron component and a gamma ray component using the direct current component and the fluctuation component of the neutron detector output. Separating circuit is provided. The characteristic value of the neutron detector necessary for this separation is obtained by irradiating the neutron detector with a standard neutron or gamma ray. By monitoring the ratio of the neutron component to the gamma ray component in the DC component and appropriately amplifying the neutron component when the ratio of the neutron component to the gamma ray component in the DC component falls below a predetermined value, neutron sensitivity The sensitivity of the neutron detector due to material consumption is corrected.
JP-A-4-218792 Japanese Patent Laid-Open No. 58-1000076 JP 59-9594 A JP-A-61-59280

  Patent document 1 assumes that the intensity | strength of the neutron flux and gamma ray flux with which a neutron detector is irradiated hardly changes. Patent Document 2, Patent Document 3 and Patent Document 4 use the characteristic value of the neutron detector obtained before being inserted into the core of the nuclear reactor.

  For this reason, in the conventional technology, when a neutron detector is inserted in a practical furnace, it is not possible to perform correction suitable for the environment of the practical furnace.

  The characteristic values such as neutron sensitivity of each neutron detector inserted in the core of a practical reactor continue to change due to, for example, exhaustion of neutron sensitive materials of the neutron detector. The neutron sensitive material is consumed according to the accumulated amount of neutron flux irradiated to the neutron detector. The intensity of the neutron flux irradiated to the neutron detector varies depending on the insertion position. Therefore, the degree of consumption of the neutron sensitive material varies depending on each neutron detector.

  Differences in the intensity of neutron flux and gamma rays irradiated to this neutron detector due to the insertion position cannot be observed unless they are actually measured in a practical furnace.

  Moreover, the temperature of a neutron detector differs between the operational furnace in operation and the experimental furnace in which the characteristic value of the neutron detector is generally measured. In general, the temperature of a neutron detector reaches about 300 ° C. in a practical furnace while it is about room temperature in an experimental furnace. For this reason, the neutron sensitivity and the gamma ray sensitivity of the neutron detector are different between the experimental reactor and the practical reactor.

  Changes in the neutron sensitivity and gamma-ray sensitivity of the neutron detector due to this change in temperature conditions cannot be observed unless they are actually measured in a practical reactor.

  Further, in the conventional technique, the lifetime is determined based on the neutron detector output obtained by one measurement. However, it is difficult to determine whether this is due to a change in the neutron flux irradiated to the neutron detector or a gas leak from the neutron detector, even if there is an abnormality in the measured value with only one measured value. is there.

  The present invention has been made in consideration of the above-described circumstances, and can accurately correct the output of a neutron detector inserted in a practical reactor, and the reactor core can be used by using the corrected neutron detector output. It is an object of the present invention to provide a neutron detector lifetime determination apparatus, a lifetime determination method thereof, and a reactor core monitoring apparatus using the lifetime determination apparatus capable of improving the monitoring performance.

  In order to solve the above-described problems, the neutron detector lifetime determination apparatus according to the present invention has a direct current in an electrical signal output from radiation detection means inserted in a nuclear reactor as described in claim 1. DC component measuring means for measuring the component, DC component history storing means for storing the measured value of the DC component as a history, and reading the history of the DC component measured value from the DC component history storing means, and correcting the history DC component correction means, fluctuation component measurement means for measuring fluctuation components in the electrical signal, fluctuation component history storage means for storing measured values of the fluctuation components as history, and fluctuation components from the fluctuation component history storage means Fluctuation component correcting means for reading the history of measured values and correcting the history is provided.

  Moreover, in order to solve the above-described problem, the lifetime determination device for a neutron detector according to the present invention provides a DC component neutron of radiation detecting means inserted in advance in a nuclear reactor as described in claim 2. Constant fluctuation means for storing sensitivity ratio to sensitivity fluctuation component neutron sensitivity, DC component measuring means for measuring DC component in electric signal output from radiation detecting means, and history of measured value of DC component DC component history storage means for storing as a DC component history storage means, and a DC component correction means for reading out the history of the DC component measurement value from the DC component history storage means and extracting and correcting sudden changes in the DC component measurement value from the history. Fluctuation component measuring means for measuring fluctuation components in the electrical signal, fluctuation component history storage means for storing measured values of the fluctuation components as history, and the DC component compensation. Fluctuation component correction means for correcting the fluctuation component history read out from the fluctuation component history storage means based on the data of the sudden change received from the means; and the constant storage in the fluctuation component after the correction. Detector characteristic determining means for obtaining the neutron component in the corrected DC component by multiplying the sensitivity ratio read from the means, the detector characteristic determining means, the corrected DC component based on the measured value history By comparing the neutron component with the neutron component, the corrected direct current component can be separated into a neutron component and a gamma ray component.

  Moreover, in order to solve the above-described problem, the method for determining the lifetime of a neutron detector according to the present invention includes an electrical signal output from radiation detection means inserted in a nuclear reactor as described in claim 13. Measuring the DC component of the step, storing the measured value of the DC component as a history, correcting the history of the measured value of the DC component, measuring the fluctuation component in the electrical signal, The method includes a step of storing the measured value of the fluctuation component as a history, and a step of correcting the history of the measured value of the fluctuation component.

  In addition, in order to solve the above-described problems, the reactor core monitoring apparatus according to the present invention has, as described in claim 14, a DC component neutron sensitivity and a radiation detection means inserted in the reactor in advance. Sensitivity storage means for storing DC component gamma ray sensitivity, DC component measurement means for measuring DC components in the electrical signal output from the radiation detection means, and DC components for storing measured values of the DC components as history A history storage unit, a DC component correction unit that reads the history of the DC component measurement value from the DC component history storage unit, extracts a sudden change in the DC component measurement value from the history, and corrects the change; and the electric signal Fluctuation component measurement means for measuring the fluctuation component in the fluctuation component, fluctuation component history storage means for storing the measurement value of the fluctuation component as a history, and the DC component correction means. Based on the sudden change data, fluctuation component correction means for correcting the fluctuation component history read from the fluctuation component history storage means, and a neutron component and a gamma ray component in the corrected DC component The neutron flux irradiated to the radiation detection means and the gamma ray flux are obtained by dividing by the DC component neutron sensitivity and the DC component gamma ray sensitivity read from the sensitivity storage means, and the neutron flux irradiated to the radiation detection means An irradiation neutron flux / gamma flux ratio calculating means for calculating a ratio of gamma ray flux is provided.

  Further, in order to solve the above-described problem, the reactor core monitoring apparatus according to the present invention has a DC component neutron sensitivity of the radiation detection means inserted in the reactor in advance as described in claim 20. Constant storage means for storing a sensitivity ratio to fluctuation component neutron sensitivity, DC component measurement means for measuring a DC component in an electric signal output from the radiation detection means, and a measured value of the DC component as a history DC component history storage means that reads out the history of the DC component measurement value from the DC component history storage means, extracts and corrects sudden changes in the DC component measurement value from the history, and the DC component correction means, Fluctuation component measuring means for measuring a fluctuation component in an electrical signal, fluctuation component history storage means for storing the measured value of the fluctuation component as a history, and the DC component correction means A plurality of neutron detector lifetime determination devices comprising fluctuation component correction means for correcting the fluctuation component history read from the fluctuation component history storage means based on the sudden change data received from Are installed in parallel, and the number of installed life judging devices is one or more each using a startup region neutron detector as the radiation detection means and one using a local output region monitor. The history of the corrected fluctuation component received from the lifetime determination device on the neutron detector side and the history of the corrected fluctuation component received from the lifetime determination device on the local output region monitor side are monitored, and the reactor is stopped. The output of the start-up region neutron detector is linear with respect to the reactor output with respect to the output of the local output region monitor at the time of start-up of the reactor. It is characterized in that it comprises an overlap region evaluation means for detecting an abnormality before it.

  A lifetime determination apparatus for a neutron detector, a lifetime determination method thereof, and a reactor core monitoring apparatus using the lifetime determination apparatus according to the present invention are installed in a practical reactor by using a history of measured values for each neutron detector. The neutron detector output can be accurately corrected, and the reactor core monitoring performance can be improved by using the corrected neutron detector output.

  DESCRIPTION OF EMBODIMENTS Embodiments of a neutron detector lifetime determination apparatus, a lifetime determination method thereof, and a reactor core monitoring apparatus according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is an overall configuration diagram illustrating a first embodiment of a lifetime determination device for a neutron detector according to the present invention.

  The life determination apparatus 10 includes a calculation unit 11 and a storage unit 12 connected to the calculation unit 11. Further, the life determination device 10 is connected to a local output region monitor (LPRM: Low Power Range Monitor) group 21 as a radiation detection means via a multiplexer 22. Further, the life determination device 10 is connected to the core performance calculation means 31.

  As a radiation detection means, in addition to LPRM, for example, a neutron detector using fission such as a start-up region neutron monitor (SRNM) can be used.

  The LPRM group 21 includes LPRMs 21a to 21d, and each LPRM is connected to a high voltage power source (not shown), and is arranged in the core of the reactor in order to monitor the neutron flux in the core of the reactor. Each LPRM of the LPRM group 21 has a function of detecting a neutron flux and converting it into an electrical signal, and supplying this electrical signal to the life determination device 10 via the multiplexer 22. Further, a high voltage power source (not shown) is connected to the life determination device 10 and has a function of writing the value of the applied voltage to each LPRM of the LPRM group 21 in the applied voltage history storage unit 12d in the storage unit 12.

  The multiplexer 22 has a function of selecting an arbitrary one of the LPRMs 21 a to 21 d of the LPRM group 21 and electrically connecting the selected LPRM and the life determination device 10. The multiplexer 22 may not be provided when the number of LPRMs constituting the LPRM group 21 is one.

  The calculation means 11 is configured by reading a program into a computer or by a required circuit, and includes a DC component measurement means 11a, a fluctuation component measurement means 11b, a DC component correction means 11c, a fluctuation component correction means 11d, and detector characteristics. It functions as a determination unit 11e and a nuclear lifetime determination unit 11f, and is further connected to the storage unit 12. The computing unit 11 has a function of reading each data in the storage unit 12 as necessary.

  The storage means 12 is computer-readable, and includes a DC component history storage means 12a, a fluctuation component history storage means 12b, an integrated neutron flux history storage means 12c, an applied voltage history storage means 12d, a frequency characteristic history storage means 12e, and a constant storage means. 12f, the gas μ storage means 12g, and the gas μ correction fluctuation component history storage means 12h are recorded.

  Next, an operation of the neutron detector lifetime determination apparatus 10 will be described.

  LPRMs 21a to 21d of the LPRM group 21 are inserted into the core of a practical reactor.

  The reaction between the neutron and the neutron sensitive substance (U-235) occurs randomly and has a statistical fluctuation component. For this reason, the output of LPRM, which is obtained by detecting the reaction between neutrons and neutron sensitive substances and converting them into electrical signals, also has a statistical fluctuation component. Therefore, the output of each LPRM of the LPRM group 21 is separated into a direct current component that is an average value of the output and a fluctuation component that is a mean square value of the temporal fluctuation of the output.

  The DC component measuring means 11a receives an electric signal from each LPRM of the LPRM group 21 via the multiplexer 22, and measures a DC component value in the electric signal. Subsequently, the DC component measuring unit 11a gives the measured DC component value to the DC component correcting unit 11c. The DC component measuring unit 11a classifies the DC component values for each LPRM of the LPRM group 21 and records or appends the DC component values to the DC component history storage unit 12a.

  The fluctuation component measuring means 11b receives an electric signal from each LPRM of the LPRM group 21 via the multiplexer 22, and measures the fluctuation component value in the electric signal. This measurement is generally referred to as Campbell measurement or MSV (Mean Square Value) measurement. Subsequently, the fluctuation component measuring unit 11b gives the measured fluctuation component value to the fluctuation component correcting unit 11d. Further, the fluctuation component measuring unit 11b classifies the fluctuation component values for each LPRM of the LPRM group 21 and records or appends them to the fluctuation component history storage unit 12b.

  As a result, DC component value and fluctuation component value histories are created in the DC component history storage unit 12a and the fluctuation component history storage unit 12b, respectively.

  The DC component measurement of the LPRM output by the DC component measurement means 11a and the fluctuation component measurement of the LPRM output by the fluctuation component measurement means 11b can be simultaneously connected and measured as shown in FIG. Alternatively, the DC component measuring unit 11a and the fluctuation component measuring unit 11b may be connected to each other by a switch or the like to perform measurement alternately.

  Further, the core performance calculation means 31 calculates the core performance to calculate the neutron flux distribution in the core, obtains the neutron flux at the insertion position of each LPRM from this distribution, adds the value of this neutron flux, and adds each LPRM. The value of the integrated neutron flux irradiated to is obtained. Subsequently, the core performance calculation means 31 classifies the accumulated neutron flux values for each LPRM of the LPRM group 21 and records or appends them to the accumulated neutron flux history storage means 12c.

  Here, core performance calculation refers to core performance calculation that is generally performed in boiling water reactors, and specifically, various physical phenomena such as neutron behavior and thermal hydraulic behavior in the core. It is a numerical calculation that simulates.

  Further, the high voltage power supply (not shown) classifies the value of the applied voltage to each LPRM of the LPRM group 21 for each LPRM of the LPRM group 21 and records or appends it to the applied voltage history storage unit 12d.

  Next, the operation of the DC component correction unit 11c and the fluctuation component correction unit 11d will be described.

  FIG. 2 is an explanatory diagram showing the relationship between the accumulated neutron flux irradiated to this LPRM and the DC component value of the output of this LPRM for any one LPRM in the LPRM group 21.

  In general, as shown in FIG. 2, the DC component of the LPRM output can be divided into a neutron component and a gamma ray component.

  The neutron component is a component derived from the fact that the fission product generated as a result of the fission of the neutron sensitive material in the LPRM ionizes the gas in the LPRM out of the LPRM output. This fission of the neutron sensitive material is induced by the reaction between the neutron sensitive material and the neutron.

  The gamma ray component is a component mainly derived from the fact that the electrons repelled from the structural material in the LPRM by the gamma rays in the core of the LPRM ionize the gas in the LPRM. In addition to this, the repelled electrons do not ionize the gas and contribute directly as a current, the radiation-induced beta rays contribute as a current, and the gamma rays directly ionize the gas in the LPRM. All LPRM outputs other than neutron components are included.

  FIG. 3A is an explanatory diagram showing the relationship between the accumulated neutron flux irradiated to the LPRM and the DC component value of the output of the LPRM when there is a gas leak.

  In a practical reactor in operation, the intensity of neutron flux and gamma rays applied to the neutron detector has an insertion position dependency.

  In addition, the change in the characteristic value of each neutron detector due to gas leakage or the like occurs variously for each individual after being inserted into the core.

  In general, the change in the output of the neutron detector due to the fluctuation of the neutron and gamma ray intensity ratio at a certain insertion position is not a sudden change such as a change in output due to gas leakage unless the control rod is operated. This is a gradual change.

  In the conventional technology for monitoring the output of a neutron detector, when the output of a neutron detector inserted at a certain position fluctuates, whether this is a sudden change due to a gas leak of the neutron detector, It is difficult to distinguish whether the intensity ratio changes between the neutron flux and gamma rays at the insertion position. Whether or not this is a sudden change can be determined by monitoring the history of measured values.

  Therefore, the measured value is recorded and a history is created, and this measured value history is used to correct the fluctuation of the neutron detector output due to the gas leak.

  The DC component correcting means 11c has a function of receiving a DC component value from the DC component measuring means 11a and information necessary for correcting the DC component value obtained from the fluctuation component value from the fluctuation component correcting means 11d. The history of the DC component value of each LPRM output of the LPRM group 21 is read from the history storage means 12a, and the value of the accumulated neutron flux irradiated to each LPRM is read from the accumulated neutron flux history storage means 12c. The time of shift is extracted as the time of gas leak occurrence.

  Subsequently, the DC component correcting means 11c obtains the change amount of the gas pressure of each LPRM from the shift amount of the DC component, corrects the history of the DC component value, and detects the history of the corrected DC component value. Is given to the vessel characteristic determination means 11e. Subsequently, the DC component correction unit 11c calculates the fluctuation component correction unit by calculating the gas leak occurrence time and the amount of change in the gas pressure of each LPRM at this point, which is information necessary for correcting the fluctuation component value obtained from the DC component value. 11d.

  FIG. 3B is an explanatory diagram showing the relationship between the accumulated neutron flux irradiated to the LPRM and the fluctuation component value after correction of the LPRM output.

  The fluctuation component correcting unit 11d has a function of receiving the fluctuation component value from the fluctuation component measuring unit 11b and the information necessary for correcting the fluctuation component value obtained from the DC component value from the DC component correcting unit 11c. The history of the fluctuation component value of each LPRM output of the LPRM group 21 is read from the history storage means 12b, and the value of the accumulated neutron flux irradiated to each LPRM is read from the accumulated neutron flux history storage means 12c.

  Further, the fluctuation component correction unit 11d corrects the fluctuation component value history using the gas leak occurrence time received from the DC component correction unit 11c and the amount of change in the gas pressure of each LPRM at this time. Then, the fluctuation component correcting unit 11d gives the history of the corrected fluctuation component value to the detector characteristic determining unit 11e.

  By the above procedure, the neutron detector lifetime determination device 10 can accurately correct the output of the neutron detector using the history of actual measurement values in a practical furnace, and by monitoring this history The gas leak of each neutron detector can be detected easily and accurately.

  Even if the neutron detector output fluctuates due to a cause other than gas leak, the fluctuation can be easily detected by monitoring the history, and the fluctuation can be corrected.

  In the present embodiment, the value of the accumulated neutron flux has only a role as an index for distinguishing each measured value when evaluating the history of each measured value. Specifically, the role as this index is, for example, a horizontal axis in a graph of DC component history and fluctuation component history of a neutron detector as shown in FIG. 2, FIG. 3 (a) or FIG. 3 (b). As a role. Even if the measurement time is used as the horizontal axis of this graph, it is possible to evaluate the history such as extraction of the occurrence point of gas leak. If the measurement interval is constant, the number of measurements is plotted on the horizontal axis of each history graph (the measurement values are plotted at equal intervals in the horizontal axis direction in the order of measurement), for example, to extract the time of occurrence of gas leak. Etc. can be evaluated. Therefore, in this embodiment, the value of the integrated neutron flux can be replaced with the measurement time or the number of measurements.

  Next, the neutron component and the gamma ray component in the DC component of each LPRM output necessary for determining the nuclear lifetime are obtained.

  First, the neutron sensitivity of the neutron detector will be described.

  The neutron sensitivity of the neutron detector is the magnitude of the neutron-derived component in the neutron detector output with respect to the neutron flux irradiated to the neutron detector, and can be divided into the neutron sensitivity of the DC component and the neutron sensitivity of the fluctuation component .

  The neutron sensitivity of the DC component and the neutron sensitivity of the fluctuation component are proportional to only the remaining amount of the neutron sensitive material when there is no sensitivity change factor other than the consumption of the neutron sensitive material. For this reason, when the direct current component neutron sensitivity is divided by the fluctuation component neutron sensitivity, a constant (hereinafter referred to as a constant B) can be obtained.

  The neutron-derived component of the neutron detector output can be divided into a neutron component in the DC component and a fluctuation component, and the neutron component in the DC component is the neutron irradiated to the neutron detector with respect to the DC component neutron sensitivity. It is a product of bundles.

  The fluctuation component has a property that is hardly affected by gamma rays. For this reason, it is assumed that the fluctuation components are all derived from neutrons. In this case, the fluctuation component is obtained by multiplying the fluctuation component neutron sensitivity by the neutron flux irradiated to the neutron detector.

  Both the neutron component and the fluctuation component in the DC component are proportional to only the neutron flux irradiated to the neutron detector. These proportionality constants are the DC component neutron sensitivity and the fluctuation component neutron sensitivity, respectively. Therefore, the constant obtained by dividing the neutron component in the DC component by the fluctuation component is equal to the constant B obtained by dividing the DC component neutron sensitivity by the fluctuation component neutron sensitivity.

  Therefore, the neutron component in the DC component can be obtained by multiplying the fluctuation component by the constant B.

  As the evaluation method of the constant B, the following three methods can be given.

  The first constant B evaluation method (hereinafter referred to as constant B evaluation method 1) calculates the ratio of the DC component neutron sensitivity to the fluctuation component neutron sensitivity (design sensitivity ratio) from the design specifications of the neutron detector. In this method, the ratio is a constant B.

  FIG. 3C illustrates the relationship between the accumulated neutron flux irradiated to the LPRM and the neutron component and the gamma ray component in the DC component after correction of the LPRM output when the constant B evaluation method 1 is applied. FIG.

  The corrected fluctuation component value attenuates as shown in FIG. Assuming that the cause of this attenuation is only the consumption of the neutron sensitive material, the ratio of the DC component neutron sensitivity to the fluctuation component neutron sensitivity relative to the fluctuation component value of the neutron detector output (constant B (design sensitivity ratio)) ), The neutron component value in the DC component of the neutron detector output can be obtained.

  First, the ratio of the DC component neutron sensitivity to the fluctuation component neutron sensitivity determined by the design specifications of the neutron detector is classified in advance for each LPRM of the LPRM group 21 and recorded as a constant B in the constant storage means 12f. .

  Further, the ratio of the gamma ray component in the direct current component to the neutron component in the direct current component to be determined as the nuclear lifetime (hereinafter referred to as the nuclear lifetime DCn / γ ratio) is recorded in the constant storage means 12f in advance. This nuclear lifetime DCn / γ ratio is a constant. The end of the nuclear lifetime of each neutron detector is detected when the ratio of the neutron component to the gamma ray component (hereinafter referred to as DCn / γ ratio) is equal to or less than the nuclear lifetime DCn / γ ratio. This DCn / γ ratio is a variable.

  In the constant B evaluation method 1, the nuclear characteristic of each LPRM is determined by the following procedure by the detector characteristic determining unit 11e and the nuclear lifetime determining unit 11f.

  The detector characteristic determining means 11e has a function of receiving the history of the corrected DC component value from the DC component correcting means 11c and the history of the corrected fluctuation component value from the fluctuation component correcting means 11d, respectively. The constant B recorded in 12f is read, and the history of the corrected fluctuation component value received from the fluctuation component correction means 11d is multiplied by this constant B to calculate the neutron component value in the DC component.

  As shown in FIG. 3C, the remaining component obtained by removing the neutron component from the entire DC component is a gamma ray component. The detector characteristic determining unit 11e calculates the gamma ray component in the DC component by comparing the calculated neutron component value in the DC component with the history of the corrected DC component value received from the DC component correcting unit 11d. To do. As a result, the detector characteristic determination unit 11e can separate the direct current component into a neutron component and a gamma ray component. The detector characteristic determination means 11e gives the neutron component and the gamma ray component in the direct current component to the nuclear lifetime determination means 11f.

  The nuclear lifetime determination unit 11f receives the neutron component and the gamma ray component in the direct current component from the detector characteristic determination unit 11e, and calculates the DCn / γ ratio by dividing the neutron component by the gamma ray component. Then, the nuclear life determination unit 11f determines that the LPRM has reached the end of life when the ratio falls below the nuclear life DCn / γ ratio recorded in the constant storage unit 12f in advance.

  According to the above procedure, the neutron detector lifetime determination device 10 can monitor the history of the neutron detector output and accurately correct the DC component and the fluctuation component, and use the accurately corrected DC component and the fluctuation component. Thus, the direct current component is separated into a neutron component and a gamma ray component. Therefore, the neutron component and the gamma ray component of the DC component separated by the lifetime determination device 10 are more accurate than those obtained by the conventional procedure, and the nuclear lifetime determination of the neutron detector can be performed.

  The neutron detector lifetime determination apparatus 10 evaluates the neutron component and the gamma ray component in the DC component of the neutron detector output while driving the neutron detector at various insertion positions in the practical reactor. Can do. Therefore, the correction for the neutron detector output reflects the individual differences of each neutron detector, and the practical reactors such as the temperature of each neutron detector, the neutron flux distribution in the core and the gamma ray flux distribution in the core. It reflects the environment.

  Next, a second constant B evaluation method (hereinafter referred to as constant B evaluation method 2) will be described.

  In the constant B evaluation method 2, a gamma ray component (hereinafter referred to as a design time gamma ray component) in the DC component of the neutron detector output evaluated by design is used.

  FIG. 4 is an explanatory diagram showing the relationship between the accumulated neutron flux irradiated to the LPRM and the neutron component and the gamma ray component in the DC component after correction of the LPRM output when the constant B evaluation method 2 is applied. .

  First, the gamma ray components at the time of design are recorded in the constant storage unit 12f in advance by classification for each LPRM of the LPRM group 21.

  Next, immediately after the LPRMs 21a to 21d of the LPRM group 21 are actually inserted into the reactor core (at the time of initial insertion), the DC component measuring means 11a measures the DC component of each LPRM output, and this measurement The value is given to the DC component correction unit 11c.

  Further, the fluctuation component measuring means 11b measures the fluctuation component value of each LPRM output, and gives it to the fluctuation component correcting means 11d.

  Next, the direct current component correcting means 11c receives the direct current component value at the time of the initial insertion from the direct current component measuring means 11a and gives it to the detector characteristic determining means 11e. Further, the fluctuation component correction unit 11d gives the fluctuation characteristic value at the time of initial insertion received from the fluctuation component measurement unit 11b to the detector characteristic determination unit 11e.

  Next, the detector characteristic determination unit 11e subtracts the design time gamma ray component value recorded in advance in the constant storage unit 12f from the initial installation DC component value received from the DC component correction unit 11c, and the initial installation operation. The neutron component in the DC component of the LPRM output at is calculated. The detector characteristic determination means 11e calculates the ratio of the initial insertion neutron component value to the initial insertion fluctuation component value received from the fluctuation component correction means 11d.

  Next, the detector characteristic determination unit 11e classifies the ratio to the fluctuation component value at the time of initial insertion as a constant B for each LPRM of the LPRM group 21 and records it in the constant storage unit 12f.

  In the constant B evaluation method 2, the LPRM output inserted in the core is detected by the detector characteristic determination means 11e and the nuclear lifetime determination means 11f using the constant B in the same procedure as the constant B evaluation method 1. The neutron component in the direct current component is obtained, and the nuclear lifetime of each LPRM is determined.

  When the constant B evaluation method 2 is applied, the lifetime determination device 10 of the neutron detector uses the constant B calculated after actually being installed in the nuclear reactor. Therefore, compared to the constant B evaluation method 1 in which the design sensitivity ratio is used as the constant B, it is possible to obtain a more accurate neutron component in the direct current component for each neutron detector, and perform a highly accurate nuclear lifetime determination. Can do.

  Next, a third constant B evaluation method (hereinafter referred to as constant B evaluation method 3) will be described.

  In the constant B evaluation method 3, a neutron detector not coated with a neutron sensitive substance is used.

  First, a normal LPRM to be installed in a practical furnace is prepared. Also, a comparative LPRM having the same shape as this LPRM and not coated with a neutron sensitive substance in the detector is prepared. The normal LPRM and the comparative LPRM are inserted into an experimental furnace, and the DC component and fluctuation component of both outputs are measured under the same irradiation conditions. The DC component of the normal LPRM output is the total value of the neutron component and the gamma ray component, while the DC component of the output of the comparative LPRM is only the gamma ray component. For this reason, the neutron component in the DC component of the LPRM output can be obtained from the comparison of both DC components.

  The ratio of the neutron component and the fluctuation component in the DC component of the LPRM output measured in the experimental furnace is classified as a constant B for each LPRM of the LPRM group 21 and recorded in advance in the constant storage means 12f.

  In the constant B evaluation method 3, the LPRM output inserted in the core is detected by the detector characteristic determination means 11e and the nuclear lifetime determination means 11f using the constant B in the same procedure as the constant B evaluation method 1. The neutron component in the direct current component is obtained, and the nuclear lifetime of each LPRM is determined.

  When the constant B evaluation method 3 is applied, the lifetime determination device 10 of the neutron detector uses the constant B calculated using the gamma ray component measured by inserting the neutron detector into the experimental furnace. For this reason, the constant B which reflected the individual difference of each neutron detector more can be used compared with the constant B evaluation method 1 which uses a design sensitivity ratio. For this reason, it is possible to obtain a more accurate neutron component in the DC component, and to perform a highly accurate nuclear lifetime determination.

  The constant B evaluated by the constant B evaluation method 1 and the constant B evaluation methods 2 and 3 may change during driving of the neutron detector. This is mainly because the fluctuation component of the neutron detector output is likely to change during the driving of the neutron detector.

  There are the following four methods for correcting the fluctuation component of the neutron detector output.

  The first fluctuation component correction method (hereinafter referred to as fluctuation component correction method 1) corrects changes in fluctuation components caused by fluctuations in the electron mobility of the ionizing gas sealed in the neutron detector. Is the method.

  FIG. 5A is an explanatory diagram showing LPRM applied voltage characteristics of the fluctuation component of the LPRM output.

  The electron mobility of the ionizing gas in the neutron detector changes when changes occur in the pressure, components, temperature, etc. of the ionizing gas. When this electron mobility change occurs, the fluctuation component of the neutron detector output changes. For this reason, the applied voltage characteristic of the fluctuation component changes according to the change in the electron mobility of the gas.

FIG. 5 (b), actually against commercial reactor neutron detectors inserted in the voltage applied during normal measurement (hereinafter, referred to as the driving voltage V _d) in the slope of the applied voltage characteristic curve of the fluctuation component FIG. 6 is an explanatory diagram showing LPRM applied voltage characteristics of a fluctuation component when increased as compared with FIG. In general, a voltage of about 100V as the driving voltage _{V d} is applied.

In the vicinity of the driving voltage V _d, and the inclination with respect to the applied voltage of the fluctuation component, the electron mobility of the gas, there is a correlation. The fluctuation component correction method 1 uses this correlation to correct the fluctuation component change caused by the change in the electron mobility of the gas.

Is previously obtained and the slope of the applied voltage characteristic curve of the fluctuation component in the vicinity of the driving voltage V _d, the correlation between the electron mobility of the gas. This correlation is unique to the neutron detector and does not depend on the installation environment of the neutron detector. Therefore, this correlation may be obtained, for example, by measuring during driving in the experimental furnace. This correlation is recorded in the gas μ storage means 12g as two-dimensional array data.

In addition, the applied voltage characteristic of the fluctuation component is measured in advance when it is used as a reference for correction (evaluation reference time). The electron mobility of the gas which can be evaluated from the slope of the driving voltage V _d of the characteristic curve, as the electron mobility of the gas during evaluation criteria, is recorded in the constant storing section 12f. Examples of the measurement at the time of the evaluation standard include measurement in a test furnace, measurement at the time of initial insertion, or latest measurement.

  The electron mobility of this gas is evaluated by the following procedure.

First, the LPRM21a~21d of LPRM group 21, from the high voltage power source (not shown), and applies an arbitrary voltage in the vicinity of the driving voltage _{V d.}

  Next, the fluctuation component measuring means 11b measures the fluctuation component of the output of each LPRM, classifies the fluctuation component value for correction with respect to the electron mobility change of this gas for each LPRM of the LPRM group 21, It is recorded in the μ correction fluctuation component history storage means 12h. However, this recording is performed by additional recording when one or more fluctuation component values for correction with respect to the change in electron mobility of the gas are recorded in the gas μ correction fluctuation component history storage means 12h.

  Further, the high voltage power source (not shown) classifies the value of the applied voltage to each LPRM of the LPRM group 21 for each LPRM of the LPRM group 21 and records it in the applied voltage history storage unit 12d. However, this recording is performed by additional recording when one or more applied voltage values are recorded in the applied voltage history storage means 12d.

The procedure up to this point, necessary to determine the slope of the curve and sweep back and forth, around the driving voltage V _d from applied voltage characteristic curve of the fluctuation component of the applied voltage to the drive voltage V _d for each LPRM of LPRM group 21 Repeat until data is collected.

Next, the fluctuation component correction unit 11d stores the history of the fluctuation component value for correction with respect to the change in electron mobility of the gas of each LPRM output of the LPRM group 21 from the fluctuation component history storage unit 12h for gas μ correction, and the applied voltage history storage. The history of the voltage applied to each LPRM is read from the means 12d. Subsequently, the fluctuation component correction unit 11d is in the driving voltage V _d, and calculates the slope of the applied voltage characteristic curve of the fluctuation component.

  Then, the fluctuation component correcting unit 11d searches the correlation two-dimensional array data to obtain the electron mobility of the gas corresponding to the calculated inclination from the gas μ storage unit 12g, and the electron of the corresponding gas. Get mobility.

  The electron mobility of the gas can be evaluated by the above procedure.

  At the time of evaluation criteria, the electron mobility of this gas is recorded in the constant storage means 12f as the electron mobility of gas at the time of evaluation criteria.

  Next, the fluctuation component is corrected using the ratio of the change in electron mobility of the gas.

  The fluctuation component correcting unit 11d reads the electron mobility of the gas at the time of the evaluation reference recorded in the constant storage unit 12f in advance, and calculates the ratio with the electron mobility of the gas obtained in the current measurement.

  Subsequently, the fluctuation component correction unit 11d reads the fluctuation component value history from the gas μ correction fluctuation component history storage unit 12h, and corrects the fluctuation component value history using the calculated ratio. Then, the fluctuation component correcting unit 11d gives the history of the corrected fluctuation component value to the detector characteristic determining unit 11e.

  In the fluctuation component correction method 1, the detector characteristic determination unit 11e and the nuclear lifetime determination unit 11f use the history of fluctuation component values after correction with respect to the change in electron mobility of the gas, similarly to the constant B evaluation method 1. In this procedure, the neutron component in the DC component of the LPRM output is obtained, and the nuclear lifetime of each LPRM is determined.

  When the fluctuation component correction method 1 is applied, the neutron detector lifetime determination apparatus 10 performs correction for fluctuation component fluctuations caused by the change in electron mobility of the ionizing gas sealed in the neutron detector. be able to. For this reason, even if the pressure, component, temperature, etc. of the gas in the neutron detector change, it is possible to obtain an accurate neutron component in the DC component, and to perform a highly accurate nuclear lifetime determination.

  When the fluctuation component correction method 1 is applied, the fluctuation component correction unit 11d detects the ratio between the slope of the calculated fluctuation component in the drive voltage of the applied voltage characteristic curve and the value at the time of initial insertion of this slope. You may give to the vessel characteristic determination means 11e.

  In this case, the fluctuation component correction means 11d reads the fluctuation component value history from the fluctuation component history storage means 12b, and does not correct the change in the electron mobility of the gas with respect to this history, and the detector characteristic determination means 11e. To give. The detector characteristic determination unit 11e corrects the value of the constant B recorded in advance in the constant storage unit 12f using the ratio received from the fluctuation component correction unit 11d. The detector characteristic determination unit 11e can obtain the neutron component in the DC component by multiplying the corrected constant B by the history of the fluctuation component value.

  That is, instead of correcting the fluctuation component value history by the fluctuation component correction means 11d, the constant B is corrected by the detector characteristic determination means 11e. The correction of the fluctuation component value history and the correction of the constant B are different in procedure, but use the same slope ratio, so the principle is exactly the same, and the value of the neutron component in the obtained DC component is also the same. The same.

  Next, a second fluctuation component correction method (hereinafter referred to as fluctuation component correction method 2) will be described.

  The fluctuation component correction method 2 is a method for correcting an error of fluctuation components caused by induced noise.

  FIG. 6 is an explanatory diagram showing the LPRM applied voltage characteristics of the fluctuation component of the LPRM output when induction noise is mixed in the neutron detector output.

  The applied voltage characteristic of the fluctuation component of the neutron detector output is normally a curve as shown in FIG. However, when external noise is induced with respect to the output of the neutron detector, the applied voltage characteristic of the fluctuation component becomes a curve as shown in FIG. In particular, the LPRM output is usually measured in a so-called two-point grounding state in which the LPRM and the measurement system are grounded separately, and noise is likely to be induced. When this induction noise is mixed, the value of the noise component is added to the fluctuation component value of the neutron detector output. As a result, the constant B, which is the ratio between the DC component and the fluctuation component, changes.

  In the fluctuation component correction method 2, the value of the fluctuation component at the applied voltage of 0 V is treated as a constant noise component with respect to the applied voltage. The noise component value is subtracted from the fluctuation component value. As a result, a fluctuation component from which the influence of noise is removed can be obtained.

  First, an applied voltage from a high voltage power source (not shown) to LPRMs 21a to 21d of the LPRM group 21 is set to 0V.

  Next, the fluctuation component measuring unit 11b measures the fluctuation component of the output of each LPRM, classifies the fluctuation component value at the applied voltage of 0 V as a noise component value for each LPRM, and records it in the constant storage unit 12f. To do.

  In the fluctuation component correction method 2, the fluctuation component value history is corrected using the noise component value.

  The fluctuation component correction unit 11d reads the fluctuation component value history from the fluctuation component history storage unit 12b and the noise component value from the constant storage unit 12f, subtracts the noise component value from the fluctuation component value, and performs noise removal correction. The fluctuation component value is obtained. Then, the fluctuation component correcting unit 11d gives the history of the fluctuation component value after the noise removal correction to the detector characteristic determining unit 11e.

  In the fluctuation component correction method 2, LPRM is performed in the same procedure as the constant B evaluation method 1 using the history of fluctuation component values after the noise removal correction by the detector characteristic determination unit 11e and the nuclear lifetime determination unit 11f. The neutron component in the direct current component of the output is obtained, and the nuclear lifetime of each LPRM is determined.

  When the fluctuation component correction method 2 is applied, the neutron detector lifetime determination apparatus 10 can remove induced noise in the neutron detector output signal. For this reason, even if induced noise is likely to be mixed into the fluctuation component value of the neutron detector output, such as when used in a so-called two-point grounding state where the neutron detector and the measurement system are grounded separately, the fluctuation component value This induced noise can be removed. Therefore, an accurate neutron component in a direct current component can be obtained, and a highly accurate nuclear lifetime determination can be performed.

  Next, a third fluctuation component correction method (hereinafter referred to as fluctuation component correction method 3) will be described.

  The fluctuation component correction method 3 is a method for correcting a change in fluctuation component caused by a change in neutron sensitivity of the fluctuation component.

  FIG. 7A is an explanatory diagram showing the frequency characteristics of the fluctuation component of the LPRM output.

  The fluctuation component of the neutron detector output has a frequency characteristic as shown in FIG. This frequency characteristic reflects the shape of the output pulse of the neutron detector. The shape of the output pulse of the neutron detector reflects the fluctuation component neutron sensitivity of the neutron detector. If the fluctuation component neutron sensitivity is high, the shape of the output pulse becomes sharp, and many high-frequency components appear as shown in FIG.

  Therefore, in the fluctuation component correction method 3, the frequency characteristic of the fluctuation component of the neutron detector output is measured, and the fluctuation of the pulse shape is estimated by spectrum analysis of the frequency characteristic. From this estimation result, the amount of change in the fluctuation component neutron sensitivity of the neutron detector is estimated, and the fluctuation component value is corrected using this estimated amount of change.

  In advance, the fluctuation component is measured when the correction is performed as a reference (evaluation reference time), and the frequency characteristic of the fluctuation component is evaluated. As the measurement at the time of this evaluation standard, for example, measurement in an experimental furnace, measurement at the time of initial insertion, or latest measurement may be mentioned.

  When selecting the pre-installation of the practical furnace at the time of the evaluation standard, the fluctuation component correcting unit 11d records the frequency characteristic of the fluctuation component in the frequency characteristic history storage unit 12e in advance for each LPRM during the measurement at the time of the evaluation standard. Keep it. However, this recording is performed by additional recording when one or more frequency characteristics are recorded in the frequency characteristic history storage unit 12e.

  Further, when selecting after the installation of the practical furnace at the time of the evaluation standard, the fluctuation component correcting unit 11d stores the frequency characteristic of the fluctuation component in the frequency characteristic history storage unit 12e for each LPRM at each measurement after the installation of the practical furnace. Record it. However, this recording is performed by additional recording when one or more frequency characteristics are recorded in the frequency characteristic history storage unit 12e.

  First, the fluctuation component measuring unit 11b receives the outputs of the LPRMs 21a to 21d of the LPRM group 21 via the multiplexer 22, and measures the fluctuation components of each LPRM output. Subsequently, the fluctuation component measuring unit 11b classifies the fluctuation component values for each LPRM and records them in the fluctuation component history storage unit 12b. However, this recording is performed by additional recording when one or more fluctuation component values are recorded in the fluctuation component history storage unit 12b.

  Further, the fluctuation component measuring unit 11b gives the measured fluctuation component to the fluctuation component correcting unit 11d.

  Next, the fluctuation component correction unit 11d evaluates the frequency characteristics of the fluctuation component received from the fluctuation component measurement unit 11b. Subsequently, the fluctuation component correcting unit 11d reads the frequency characteristic of the fluctuation component obtained at the time of the evaluation reference from the frequency characteristic history storage unit 12e, compares the respective spectrum analysis results, and relatively changes the fluctuation component neutron sensitivity. Calculate the ratio.

  Subsequently, the fluctuation component correction unit 11d reads the fluctuation component value history from the fluctuation component history storage unit 12b. The fluctuation component correction means 11d divides this fluctuation component value history by the relative change ratio of the fluctuation component neutron sensitivity obtained from the frequency characteristic change of the fluctuation component, so that the fluctuation component value due to the fluctuation of the fluctuation component neutron sensitivity is obtained. To compensate for changes. Subsequently, the fluctuation component correction unit 11d gives the history of the corrected fluctuation component value to the detector characteristic determination unit 11e.

  In the fluctuation component correction method 3, the detector characteristic determination unit 11e and the nuclear lifetime determination unit 11f use the history of the fluctuation component value after correction for the fluctuation component neutron sensitivity change, and the same as the constant B evaluation method 1. In the procedure, the neutron component in the DC component of the LPRM output is obtained, and the nuclear lifetime of each LPRM is determined.

  When the fluctuation component correction method 3 is applied, the lifetime determination device 10 of the neutron detector responds to a change in fluctuation component neutron sensitivity caused by, for example, a change in electron mobility of the ionizing gas sealed in the neutron detector. Correction can be performed. For this reason, even if the pressure, component, temperature, etc. of the gas in the neutron detector change, it is possible to obtain an accurate neutron component in the DC component, and to perform a highly accurate nuclear lifetime determination.

  Next, a fourth fluctuation component correction method (hereinafter referred to as fluctuation component correction method 4) will be described.

  The fluctuation component correction method 4 is a method for correcting attenuation of fluctuation components caused by a cable.

  The fluctuation component of the neutron detector output is attenuated according to the length of the cable connecting the neutron detector and the measurement system. The attenuation of the fluctuation component according to the cable length causes a measurement error.

  FIG. 8A is a flowchart showing a procedure for evaluating the attenuation amount of the fluctuation component due to the cable, and the reference numerals with numerals in the figure are the steps of the flowchart.

  First, in step S1, a pulse is applied to the cable so as to go from the life determination device 10 to the target LPRM.

  Further, in step S2, laying data such as the length and presence / absence of a connector is acquired from the cable laying database of the nuclear power plant for the cable connecting the life determination device 10 and the target LPRM.

  Next, in step S3, the cable length to the target LPRM is calculated from the reflected wave of the pulse applied in step S1.

  Moreover, you may obtain | require the cable length to object LPRM using the cable laying database of a nuclear power plant. In this case, in step S3, the cable length from the life determination device 10 to the target LPRM is obtained from the cable laying data acquired in step S2.

  FIG. 8B is an explanatory diagram showing signal attenuation data representing the relationship between the frequency of the installed cable and the attenuation rate.

  In step S4, the length of the cable connecting the life determination device 10 obtained in step S3 and the target LPRM is used to refer to the signal attenuation data of the cable as shown in FIG. To evaluate.

  Next, in step S5, it is checked from the cable laying data acquired in step S2 whether a connector or the like is used for the cable from the life determination device 10 to the target LPRM.

  Next, in step S6, the attenuation of the fluctuation component by the connector or the like is evaluated using the information on the connector or the like examined in step S5.

  Next, in step S7, the attenuation of the fluctuation component evaluated in step S4 and step S6 is added, and the total attenuation amount of the fluctuation component by the cable and connector laid between the life determination device 10 and the target LPRM is calculated. calculate.

  In step S8, the total attenuation amount of the fluctuation component by this cable is given to the fluctuation component correction means 11d.

  By the above procedure, data necessary for correcting the attenuation of the fluctuation component by the cable can be given to the fluctuation component correction means 11d.

  The fluctuation component correction unit 11d corrects the fluctuation component value history using the total attenuation amount of the fluctuation component by the cable.

  In the fluctuation component correction method 4, the detector characteristic determination unit 11e and the nuclear lifetime determination unit 11f use the history of fluctuation component values after correction for fluctuation component fluctuations caused by the cable, as in the constant B evaluation method 1. In this procedure, the neutron component in the DC component of the LPRM output is obtained, and the nuclear lifetime of each LPRM is determined.

  When the fluctuation component correction method 4 is applied, the neutron detector lifetime determination device 10 can correct fluctuation component attenuation by a cable, a connector, or the like laid between the neutron detector and the measurement system. For this reason, the fluctuation component which correct | amended attenuation by a cable can be calculated | required irrespective of the insertion position of a neutron detector. Therefore, an accurate neutron component in a direct current component can be obtained, and a highly accurate nuclear lifetime determination can be performed.

  In this embodiment, the constant B evaluation method 1, the constant B evaluation method 2, the constant B evaluation method 3, the fluctuation component correction method 1, the fluctuation component correction method 2, the fluctuation component correction method 3, and the fluctuation component correction method 4, They may be applied in any combination.

[Second Embodiment]
FIG. 9 is an overall configuration diagram showing a second embodiment of the lifetime determination device for a neutron detector according to the present invention.

  The life determination device 10A shown in this embodiment is configured to monitor the time response of the neutron detector output. The elapsed time providing means 33 is connected to the life determination device 10 and the life determination device 10 stores the data. The elapsed time history storage means 12i is further recorded in the means 12. The same components as those of the life determination device 10 shown in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

The control rod operation information acquisition means 32 can be constructed by reading a program into a computer, or can be configured by a required circuit, and is connected to the elapsed time providing means 33. The elapsed time providing means 33 includes: When the program is read into the computer or constituted by a required circuit, it is connected to the life determination device 10A.

  The control rod operation information acquisition means 32 has a function of acquiring the time when this operation is performed when the control rod is operated. Further, the control rod operation information acquisition means 32 has a function of giving the information at the time of the operation to the elapsed time providing means 33.

  The elapsed time providing unit 33 has a function of receiving information on the operation time of the control rod from the control rod operation information acquiring unit 32 and obtaining a time elapsed after the operation of the control rod (hereinafter referred to as an elapsed time). The elapsed time providing unit 33 has a function of writing the elapsed time in the elapsed time history storage unit 12i.

  Next, the operation of the neutron detector lifetime determination apparatus 10A will be described.

  First, an immediate component and a late component of a direct current component, which are necessary for performing life determination in the present embodiment, will be described.

  FIG. 10A is an explanatory diagram showing a relative comparison of the time responses of the DC component and fluctuation component of the LPRM output. Since the DC component value and the fluctuation component value have different scales, the DC component value or the fluctuation component value is appropriately enlarged or reduced in FIG.

  As shown in FIG. 10A, since the fluctuation component is almost entirely derived from neutrons, it reaches a constant value within a few seconds after the operation of the control rod.

  On the other hand, the direct current component includes a gamma ray component in addition to the neutron component. The gamma ray component can be divided into a component derived from prompt gamma rays and a component derived from delayed gamma rays.

  The direct current component slowly increases in the range of several minutes to several tens of minutes due to the influence of the delayed gamma ray component even after the neutron component and prompt gamma ray component reach a constant value after the control rod operation. For this reason, the time response of the direct current component is a curve as shown in FIG.

  Therefore, the direct current component is divided into a total of the neutron component and prompt gamma ray component (hereinafter referred to as prompt component) and a delayed gamma ray component (hereinafter referred to as late component).

  If the DC component is measured at the elapsed time when the fluctuation component reaches a constant value, the prompt component value of the DC component can be obtained. Further, the delayed component value can be obtained by subtracting the prompt component value from the direct current component value obtained by measuring several minutes after this elapsed time.

  By monitoring the late component in the DC component, a history of the DC component as shown in FIG. 10B can be obtained.

  In the present embodiment, when determining the lifetime of the neutron detector, the ratio of the delayed component to the entire DC component (hereinafter referred to as the delayed component ratio) is used.

  First, the value of the ratio of the delayed component to the entire DC component to be determined as the lifetime (hereinafter referred to as the lifetime delayed component ratio) is recorded in advance in the constant storage means 12f.

  The control rod operation information acquisition means 32 monitors the operation status of the control rod, and when the control rod is operated, acquires the time when this operation was performed (hereinafter referred to as control rod operation time). Subsequently, the control rod operation information acquisition unit 32 provides the acquired control rod operation time information to the elapsed time providing unit 33.

  Next, the elapsed time providing means 33 measures the measurement time each time each LPRM output of the LPRM group 21 is measured, and calculates the elapsed time calculated from the control rod operation time received from the control rod operation information acquisition means 32. To do. Subsequently, the elapsed time providing means 33 classifies the elapsed time for each LPRM of the LPRM group 21 and records it in the elapsed time history storage means 12i. However, this recording is made by appending when one or more elapsed times are recorded in the elapsed time history storage means 12i.

  The DC component correction unit 11c reads the DC component value history of each LPRM output of the LPRM group 21 from the DC component history storage unit 12a and the elapsed time from the elapsed time history storage unit 12i. Subsequently, the DC component correcting unit 11c gives the DC component history to the detector characteristic determining unit 11e as two-dimensional array data of elapsed time and DC component values.

  Further, the fluctuation component correction unit 11d reads the fluctuation component value history of each LPRM output of the LPRM group 21 from the fluctuation component history storage unit 12b, and the elapsed time from the elapsed time history storage unit 12i. Subsequently, the fluctuation component correction unit 11d gives the fluctuation component history to the detector characteristic determination unit 11e as two-dimensional array data of elapsed time and fluctuation component values.

  Next, the detector characteristic determination unit 11e evaluates an elapsed time when the fluctuation component value is constant from the history of fluctuation component values received from the fluctuation component correction unit 11d. Subsequently, the detector characteristic determination unit 11e determines the prompt component value, which is the DC component value at this elapsed time, and the DC component after a few minutes from this elapsed time, from the history of the DC component value received from the DC component correction unit 11c. Find the value. Subsequently, the detector characteristic determination unit 11e calculates the delayed component value by subtracting the prompt component value from the DC component value after a few minutes from this elapsed time. Subsequently, the detector characteristic determining means 11e gives the prompt component and the delayed component of the direct current component to the nuclear life determining means 11f.

  Subsequently, the nuclear life determination unit 11f receives the immediate component and the late component of the DC component from the detector characteristic determination unit 11e, and obtains the late component ratio by dividing the sum of both by the late component. Then, the nuclear life determination means 11f compares this ratio with the life delay component ratio recorded in the constant storage means 12f in advance, and if it falls below the life delay component ratio, it determines that the LPRM has reached the life. .

  By the above procedure, the neutron detector nuclear lifetime can be determined by comparing the neutron component, prompt gamma ray component, and delayed gamma ray component in the DC component of the neutron detector output.

  According to this neutron detector lifetime determination apparatus 10A, it is possible to distinguish and measure the direct current component of the neutron detector output into an immediate component (neutron component and prompt gamma ray component) and a delayed component (delayed gamma ray component). It is. For this reason, the lifetime of the neutron detector can be determined from the ratio of the prompt component and the delayed component.

  Therefore, according to this lifetime determination apparatus 10A, accurate and accurate nuclear lifetime determination can be performed for each neutron detector in consideration of delayed gamma rays.

[Third Embodiment]
FIG. 11 is an overall configuration diagram showing a third embodiment of the lifetime determination device for a neutron detector according to the present invention.

  The lifetime determination apparatus 10B shown in this embodiment is configured to monitor the replacement time of the neutron detector by determining the nuclear lifetime and the structural lifetime of the neutron detector. This life determination device 10B is different from the life determination device 10 shown in the first embodiment in the data given to the life determination device 10 of the core performance calculation means 31 and the calculation means 11. Since other configurations and operations are not different from those of the life determination device 10, the same components are denoted by the same reference numerals and description thereof is omitted.

  In addition, when the welded part of the case of the LPRM group 21 has reached the structural life, only the case of the LPRM group 21 may be replaced if only the case of the LPRM group 21 is replaceable, and each LPRM of the LPRM group 21 is included. All of the devices related to the LPRM group 21 may be replaced. In this embodiment, the structural life of the case of the LPRM group 21 is assumed to be the same as the structural life of each LPRM.

  The calculating means 11 of the neutron detector lifetime determining device 10B includes a DC component measuring means 11a, a fluctuation component measuring means 11b, a DC component correcting means 11c, a fluctuation component correcting means 11d, a detector characteristic determining means 11e, and a nuclear lifetime determining means. 11f, detector irradiation amount evaluating means 11g, structural lifetime determining means 11h and detector lifetime determining means 11i, and further connected to the storage means 12.

  The storage means 12 is computer-readable, and includes a DC component history storage means 12a, a fluctuation component history storage means 12b, an integrated neutron flux history storage means 12c, an applied voltage history storage means 12d, a frequency characteristic history storage means 12e, and a constant storage means. 12f, a gas μ storage means 12g, a gas μ correction fluctuation component history storage means 12h, and a fuel exchange plan storage means 12j at the next regular inspection are recorded.

  The fuel replacement plan storage means 12j at the next regular inspection records data of fuel replacement performed in the next periodic inspection.

  The core performance calculation means 31 calculates the current core neutron flux distribution by calculating the core performance, obtains the current irradiation neutron flux at the insertion position of each LPRM from this distribution, and irradiates this neutron flux with the detector. The amount is given to 11 g. Further, the core performance calculation means 31 calculates the value of the integrated neutron flux irradiated to each LPRM by integrating the neutron flux, and stores the value of the integrated neutron flux in the integrated neutron flux history storage means 12c in the storage means 12. Has a writing function.

  Here, the present represents a temporary point at which measurement is performed. Moreover, in this embodiment, a neutron flux means a thermal neutron flux.

  The detector characteristic determination unit 11e uses the corrected DC component value received from the DC component correction unit 11c, the corrected fluctuation component value received from the fluctuation component correction unit 11d, and the constant read from the constant storage unit 12f. Each LPRM of the LPRM group 21 has a function of separating the neutron component and the gamma ray component in the DC component of the output electric signal. The detector characteristic determining unit 11e has a function of supplying the neutron component and the gamma ray component to the nuclear lifetime determining unit 11f and the neutron component to the detector irradiation amount determining unit 11g, respectively.

  The nuclear lifetime determination unit 11f uses the neutron component and the gamma ray component in the DC component received from the detector characteristic determination unit 11e and the constant read from the constant storage unit 12f to determine the nuclear lifetime of each LPRM. Has the function to perform. Further, the nuclear lifetime determination unit 11f has a function of giving the determination result of the nuclear lifetime to the detector lifetime determination unit 11i.

  The detector irradiation amount determination means 11g divides the neutron component in the DC component received from the detector characteristic determination means 11e by the current irradiation neutron flux at the insertion position of each LPRM received from the core performance calculation means 31. Thus, it has a function of obtaining the DC component neutron sensitivity of each LPRM. Further, the detector dose determining means 11g calculates the accumulated neutrons irradiated to each LPRM from the amount of change of the DC component neutron sensitivity from the value at the time of initial insertion recorded in the constant storage means 12f in advance. It has a function to obtain a bundle.

  Moreover, the detector irradiation amount determination means 11g estimates the integrated irradiation amount of fast neutrons for each LPRM from this integrated neutron flux, and the fast neutrons to the welded part of the case of the LPRM group 21 in which the LPRMs 21a to 21d are stored. It has a function to calculate the integrated dose. And the detector irradiation amount determination means 11g has a function which gives the structural irradiation determination means 11h the integrated irradiation amount of the fast neutron with respect to this welding part.

  The structural life determination means 11h is used when performing the structural life determination read from the constant dose storage means 12f and the cumulative irradiation dose of fast neutrons to the welded portion of the LPRM group 21 case received from the detector dose determination means 11g. It has a function of determining the structural life of each LPRM by comparing the accumulated irradiation dose of fast neutrons (hereinafter referred to as structural life dose) to the welded portion of the case of the LPRM group 21 serving as a reference. Further, the structural lifetime determining means 11h has a function of giving the structural lifetime determination result to the detector lifetime determining device 11i.

  Next, the detector life determination device 11i will be described.

  FIG. 12 is a diagram illustrating a configuration of the detector lifetime determining device 11i of the neutron detector lifetime determining device 10B illustrated in FIG.

  The detector life determination means 11i functions as the next regular inspection dose evaluation means 11i1, the next regular inspection life determination means 11i2, the second regular inspection dose evaluation means 11i3, the second regular inspection life determination means 11i4, and the exchange detector presenting means 11i5. To do. Receiving the nuclear life determination result of each LPRM from the nuclear life determination means 11f and the structural life determination result of each LPRM from the structural life determination means 11h, respectively, the life of the LPRM is determined from these results.

  The next regular inspection dose evaluation means 11i1 receives the current in-core neutron flux distribution from the core performance calculation means 31, and predicts the neutron flux irradiated to each LPRM from the present to the next periodic inspection. Thus, the integrated neutron flux for each LPRM at the start of the next periodic inspection is predicted.

  The next regular inspection life determination means 11i2 corrects the current DCn / γ ratio received from the nuclear life determination means 11f with the predicted integrated neutron flux for each LPRM at the start of the next periodic inspection, and at the start of the next periodic inspection. It has a function of predicting the DCn / γ ratio of each LPRM. From this predicted DCn / γ ratio, the next regular inspection life determination means 11i2 has a function of determining whether or not each LPRM reaches the nuclear life at the start of the next periodic inspection.

  Further, the next regular inspection life determination means 11i2 predicts the accumulated fast neutron dose to the welded portion of the case of the current LPRM group 21 received from the structural life determination means 11h for each LPRM at the start of the next periodic inspection. It has a function of correcting the accumulated neutron flux and predicting the accumulated dose of fast neutrons to the welded portion of the case of the LPRM group 21 at the start of the next periodic inspection. From the estimated integrated dose of fast neutrons, the next regular inspection life determination means 11i2 has a function of determining whether the LPRM group 21 reaches a structural life at the start of the next periodic inspection.

  The successive rounds of irradiation dose evaluation means 11i3 receives the current core neutron flux distribution and the core neutron flux distribution at the start of the next periodic inspection from the core performance calculation means 31, and between the present and the next periodic inspection. By predicting the neutron flux irradiated to each LPRM, it has a function of predicting the accumulated neutron flux for each LPRM at the start of the next periodic inspection.

  The successive periodic inspection life determination means 11i4 corrects the current DCn / γ ratio received from the nuclear life determination means 11f with the predicted integrated neutron flux for each LPRM at the start of the subsequent periodic inspection, and at the start of the subsequent periodic inspection. It has a function of predicting the DCn / γ ratio of each LPRM. From this predicted DCn / γ ratio, the successive periodic inspection life determination means 11i4 has a function of determining whether or not each LPRM reaches the nuclear lifetime at the start of the periodic inspection after the next.

  Further, the successive periodic inspection life determination means 11i4 predicts the accumulated fast neutron dose to the welded portion of the case of the current LPRM group 21 received from the structural life determination means 11h for each LPRM at the start of the subsequent periodic inspection. It has a function of correcting the accumulated neutron flux and predicting the accumulated dose of fast neutrons to the welded portion of the case of the LPRM group 21 at the start of periodic inspections one after another. From the predicted integrated dose of fast neutrons, the successive rounds of inspection life determination means 11i4 has a function of determining whether the LPRM group 21 reaches the structural lifetime at the start of the subsequent periodic inspection.

  The exchange detector presenting means 11i5 receives the information from the next regular inspection life determination means 11i2 and the subsequent regular inspection life determination means 11i4, and the LPRM determined to have a lifetime between the next periodic inspection and the subsequent periodic inspection. Therefore, it is determined that it is necessary to replace at the next periodic inspection, and a function of presenting the fact to the user is displayed by displaying it on a necessary display or the like.

  Next, the operation of the neutron detector lifetime determination device 10B will be described.

  FIG. 13 is a flowchart showing a procedure for performing the nuclear lifetime determination and the structural lifetime determination necessary for determining the lifetime of the neutron detector by the lifetime determination apparatus 10B of the neutron detector shown in FIG. In FIG. 13, reference numerals with numerals in S in the figure represent steps in the flowchart.

  In this procedure, the detector characteristic determination unit 11e receives the corrected DC component value received from the DC component correction unit 11c and the corrected fluctuation component received from the fluctuation component correction unit 11d according to the procedure shown in the first embodiment. It starts when the neutron component and the gamma ray component in the DC component of the output electrical signal are separated for each LPRM of the LPRM group 21 using the constants read from the value and constant storage means 12f.

  Moreover, in addition to the nuclear lifetime DCn / γ ratio and the like, the constant storage means 12f stores in advance the DC component neutron sensitivity of each neutron detector at the time of initial insertion and the structural lifetime irradiation amount of the LPRM group 21. Keep it.

  First, in step S11, the nuclear lifetime determination unit 11f uses the neutron component and the gamma ray component in the DC component received from the detector characteristic determination unit 11e, and the constant read from the constant storage unit 12f to perform the first implementation. The nuclear life of each LPRM is determined according to the procedure shown in the embodiment. Subsequently, the nuclear lifetime determination unit 11f gives the determination result of the nuclear lifetime to the detector lifetime determination unit 11i.

  In step S12, the core performance calculation means 31 calculates the current core neutron flux distribution by performing core performance calculation, and obtains the current irradiation neutron flux at the insertion position of each LPRM from this distribution. The neutron flux is given to the detector dose evaluation means 11g.

  Next, in step S13, the detector irradiation amount determination unit 11g receives the neutron component in the DC component received from the detector characteristic determination unit 11e at the current insertion position of each LPRM received from the core performance calculation unit 31. The DC component neutron sensitivity of each LPRM is obtained by dividing by the irradiation neutron flux.

  Next, in step S14, the detector dose determining means 11g determines the direct current component neutron sensitivity from the amount of change from the initial insertion value recorded in the constant storage means 12f in advance for each LPRM. The irradiated integrated neutron flux is obtained.

  The decrease in neutron sensitivity is due to the consumption of neutron sensitive materials. The consumption of neutron sensitive materials is due to irradiation of neutron flux. For this reason, this integrated neutron flux calculated from the decrease in neutron sensitivity is accurate reflecting individual differences of each LPRM.

  Next, in step S15, the detector irradiation amount determination means 11g calculates the integrated irradiation amount of fast neutrons for each LPRM from the integrated neutron flux. This calculation can be performed by assuming that the ratio of the intensity of fast neutrons to the intensity of thermal neutrons detected by the neutron detector is constant throughout the reactor. That is, by multiplying the integrated neutron flux obtained in step S4 by this intensity ratio, the integrated dose of fast neutrons for each LPRM can be calculated.

  Next, in step S16, the detector irradiation amount determination means 11g uses the integrated fast irradiation of fast neutrons for each LPRM as the fast irradiation of fast neutrons to the welded portion of the LPRM group 21 in which LPRMs 21a to 21d are stored. Convert to quantity. Subsequently, the detector irradiation amount determination unit 11g gives the structural life determination unit 11h the integrated irradiation amount of fast neutrons for the weld.

  Next, in step S17, the structural life determination means 11h receives the accumulated fast dose of fast neutrons from the welded portion of the LPRM group 21 case received from the detector dose determination means 11g and the structure read from the constant storage means 12f. The structural lifetime of the LPRM group 21 is determined by comparing the lifetime with the effective lifetime. Subsequently, the structural lifetime determination unit 11h gives the determination result of the structural lifetime to the detector lifetime determination device 11i.

  In step S18, the detector lifetime determination unit 11i determines the lifetime of each LPRM based on the results of the nuclear lifetime determination and the structural lifetime determination.

  By the above procedure, it is possible to perform the nuclear lifetime determination and the structural lifetime determination necessary for determining the lifetime of the neutron detector.

  Next, the life determination of each LPRM performed in step S18 shown in FIG. 13 will be described in detail.

  FIG. 14 is a flowchart showing a procedure for determining the lifetime of the neutron detector by the lifetime determination device 10B of the neutron detector and presenting the neutron detector determined to have a lifetime. In FIG. 14, reference numerals with numerals in S in the figure represent steps in the flowchart.

  In this procedure, the nuclear life determination means 11f provided the DCn / γ ratio, and the structural life determination means 11h provided the accumulated irradiation dose of fast neutrons to the welded portion of the case of the LPRM group 21 to the detector life determination means. Start at the point.

  First, in step S21, the core performance calculation means 31 obtains the current irradiation neutron flux at the insertion position of each LPRM from the current core neutron flux distribution calculated by performing the core performance calculation, and this neutron flux is obtained. This is given to the next regular inspection dose evaluation means 11i1.

  Next, in step S22, the next regular inspection dose evaluation means 11i1 receives the current in-core neutron flux distribution from the core performance calculation means 31, and irradiates each LPRM between the present and the next periodic inspection. By predicting the neutron flux to be performed, the integrated neutron flux for each LPRM at the start of the next periodic inspection is predicted. Subsequently, the next regular inspection dose evaluation means 11i1 gives this predicted integrated neutron flux to the next regular inspection life determination means 11i2.

  Next, in step S23, the next regular inspection life determination means 11i2 corrects the current DCn / γ ratio received from the nuclear life determination means 11f with the predicted integrated neutron flux for each LPRM at the start of the next periodic inspection. The DCn / γ ratio of each LPRM at the start of the next periodic inspection is predicted. Further, the next regular inspection life determination means 11i2 predicts the accumulated fast neutron dose to the welded portion of the case of the current LPRM group 21 received from the structural life determination means 11h for each LPRM at the start of the next periodic inspection. Corrected by the accumulated neutron flux, the accumulated dose of fast neutrons to the welded part of the case of the LPRM group 21 at the start of the next periodic inspection is predicted.

  Next, in step S24, the next regular inspection life determination means 11i2 compares the predicted DCn / γ ratio of each LPRM at the start of the next periodic inspection with the nuclear life DCn / γ ratio read from the constant storage means. For each LPRM, it is determined whether or not the nuclear lifetime will be reached at the start of the next periodic inspection.

  Further, the next regular inspection life determination means 11i2 is configured to predict the fast accumulated neutron dose to the welded portion of the LPRM group 21 case at the start of the next periodic inspection and the structural life irradiation dose of the LPRM group 21 read from the constant storage means. Are compared, it is determined whether the LPRM group 21 will reach the structural life at the start of the next periodic inspection.

  On the other hand, in step S25, the core performance calculation means 31 determines the insertion position of each LPRM from the current core neutron flux distribution calculated by performing the core performance calculation and the core neutron flux distribution at the start of the next periodic inspection. The current irradiation neutron flux and the irradiation neutron flux at the start of the next periodic inspection are obtained, and this neutron flux is given one after another to the routine inspection dose evaluation means 11i3.

  Here, the core performance calculation means 31 uses the fuel exchange data read from the fuel exchange plan storage means 12j at the next regular inspection when calculating the in-core neutron flux distribution at the start of the next periodic inspection. The core performance calculation means 31 obtains the fuel condition at the start of the next periodic inspection from the fuel exchange data, calculates the neutron flux distribution in the core under this fuel condition by the core performance calculation, and the core at the start of the next periodic inspection. Calculate the inner neutron flux distribution.

  Next, in step S26, the routine inspection dose evaluation means 11i3 successively receives the current core neutron flux distribution and the core neutron flux distribution at the start of the next periodic inspection from the core performance calculation means 31, and continues from the current time. By estimating the neutron flux irradiated to each LPRM before the periodic inspection, the cumulative neutron flux for each LPRM at the start of the next periodic inspection is predicted. Subsequently, the successive periodic inspection dose evaluation means 11i3 gives this accumulated neutron flux to the successive periodic inspection life determination means 11i4.

  Next, in step S27, the second regular inspection life determination means 11i4 corrects the current DCn / γ ratio received from the nuclear life determination means 11f with the predicted integrated neutron flux for each LPRM at the start of the next periodic inspection. The DCn / γ ratio of each LPRM is predicted at the start of the periodic inspection one after another. Further, the successive periodic inspection life determination means 11i4 predicts the accumulated fast neutron dose to the welded portion of the case of the current LPRM group 21 received from the structural life determination means 11h for each LPRM at the start of the subsequent periodic inspection. Corrected by the accumulated neutron flux, the accumulated dose of fast neutrons to the welded part of the case of the LPRM group 21 at the start of periodic inspections one after another is predicted.

  Next, in step S28, the regular inspection life determination means 11i4 after each time compares the predicted DCn / γ ratio of each LPRM at the start of the subsequent periodic inspection with the nuclear life DCn / γ ratio read from the constant storage means. Then, for each LPRM, it is determined whether or not the nuclear life is reached at the start of the periodic inspection one after another.

  Further, the successive periodic inspection life determination means 11i4 is configured to predict the fast integrated neutron dose to the welded portion of the LPRM group 21 case at the start of the subsequent periodic inspection, and the structural lifetime irradiation dose of the LPRM group 21 read from the constant storage means. Are compared, it is determined whether the LPRM group 21 will reach the structural life at the start of the next periodic inspection.

  Next, in step S29, the replacement detector presenting means 11i5 receives information on the life from the next regular inspection life determination means 11i2 and the subsequent regular inspection life determination means 11i4, and the nucleus is detected between the next periodic inspection and the next periodic inspection. It is determined that it is necessary to replace the LPRM that is determined to reach the target lifetime or structural lifetime at the next periodic inspection, and this is displayed to the user by displaying it on a required indicator or the like.

  According to the above procedure, the lifetime of the neutron detector is determined, and the neutron detector determined to reach the lifetime between the next periodic inspection and the next periodic inspection can be presented to the user.

  This neutron detector lifetime determination device 10B can determine the neutron component in the DC component based on the actual measurement value for each neutron detector by monitoring the history of the output of the neutron detector. Life assessment can be performed.

  Conventionally, the accumulated neutron flux that has been used for structural lifetime determination is obtained by integrating based on the in-core neutron flux distribution obtained by the core performance calculation. Therefore, when the irradiation conditions for each neutron detector change due to fuel shuffling, etc., it is necessary to manage the accurate irradiation history of each neutron detector. It is difficult to obtain accurately.

  On the other hand, this lifetime determination apparatus 10B can obtain the current DC component neutron sensitivity from the current irradiation neutron flux intensity using the neutron component value in the DC component that can be separated by using the measurement history. For this reason, the lifetime determination apparatus 10B can directly calculate the accurate integrated neutron flux directly from the amount of decrease in the current DC component neutron sensitivity from the initial insertion.

  Therefore, in this lifetime determination device 10B, the neutron flux distribution and gamma ray distribution in the core change due to fuel shuffling, etc., and the irradiation neutron flux intensity and gamma ray intensity at the insertion position of each LPRM change. Even if the intensity ratio changes, an accurate integrated neutron flux can be easily obtained.

  According to the lifetime determination apparatus 10B, it is possible to perform a structural lifetime determination with high accuracy by using an accurate irradiation accumulated neutron flux for each LPRM.

  Therefore, the lifetime determination apparatus 10B can accurately determine the nuclear lifetime and the structural lifetime, and can accurately determine the lifetime of each LPRM using these determination results.

  Utilizing this accurate life determination, the life determination device 10B can predict the life at the next periodic inspection and the subsequent periodic inspection, and can accurately present the replacement time.

[Fourth Embodiment]
FIG. 15: is a whole block diagram which shows 4th Embodiment of the lifetime determination apparatus of the neutron detector which concerns on this invention.

  The reactor core monitoring device 20 using the neutron detector lifetime determination device 10 shown in this embodiment can optimize the void ratio around the neutron detector. In this embodiment, the life determination device 10 is the same as the life determination device 10 shown in FIG. 1 except that the output to the neutron flux distribution correction means 40 is different from the life determination device 10 shown in the first embodiment. In order to achieve the above effects, the same components are denoted by the same reference numerals and description thereof is omitted.

  The reactor core monitoring device 20 includes a life determination device 10, an LPRM group 21, a multiplexer 22, a core performance calculation unit 31, and a neutron flux distribution correction unit 40.

  The neutron flux distribution correction means 40 includes a calculation means 41 and a storage means 42, and is connected to the life determination device 10 and the core performance calculation means 31.

  The detector characteristic determination unit 11e of the lifetime determination apparatus 10 has a function of supplying the neutron flux distribution correction unit 40 with the neutron component and the gamma ray component in the direct current component.

  The calculation means 41 is configured by reading a program into a computer or a required circuit, and functions as an irradiation n / γ ratio calculation means 41a and a peripheral void ratio evaluation means 41b, and is further connected to a storage means 42. . The calculation means 41 has a function of reading data in the storage means 42 as necessary.

  The storage means 42 is computer-readable and has a function of recording the sensitivity storage means 42a and the void ratio storage means 42b.

  The irradiation n / γ ratio calculation means 41a receives the DC component history and fluctuation component history of each LPRM received from the detector characteristic determination means 11e, and the DC component neutron sensitivity and gamma ray of each LPRM read from the sensitivity storage means 42a. Using the sensitivity, it has a function of obtaining the ratio of the neutron flux to the gamma ray flux at the insertion position of each LPRM. Further, the irradiation n / γ ratio calculating means 41a has a function of giving the calculated ratio to the peripheral void ratio evaluating means 41b.

  The peripheral void ratio evaluating means 41b has a function of searching for a ratio for each LPRM received from the irradiation n / γ ratio calculating means 41a according to the void ratio storage means 42b and acquiring a void ratio corresponding to this ratio. Further, the peripheral void ratio evaluation means 41 b has a function of giving the core performance calculation means 31 the value of the void ratio around each LPRM.

  The core performance calculation means 31 receives the value of the void ratio around each LPRM from the neutron flux distribution correction means 40, and calculates the core performance based on the void ratio value, thereby obtaining the in-core neutron flux distribution of the reactor. It has a function. Further, the core performance calculation means 31 obtains the neutron flux at the insertion position of each LPRM from this distribution, obtains the value of the accumulated neutron flux irradiated to each LPRM by accumulating the value of this neutron flux, It has a function of writing the value of the bundle into the integrated neutron flux history storage means 12c in the storage means 12.

  Next, the operation of the reactor core monitoring apparatus 20 using the neutron detector lifetime determination apparatus 10 will be described.

  First, the relationship between the neutron flux and gamma rays irradiated to the LPRM and the void ratio will be described.

  The emission intensity of neutrons and gamma rays from the fuel takes almost constant known values. Therefore, the intensity ratio of the neutron flux and the gamma ray flux at the time of emission is a substantially constant known value.

  The reactivity to water differs between neutrons and gamma rays. For this reason, the intensity ratio of the neutron flux and the gamma ray flux that passes through the void and reaches (irradiates) the LPRM varies depending on the void ratio.

  Therefore, it is possible to relate the void ratio to the ratio of the neutron flux and the gamma ray flux that passes through the void and irradiates the LPRM (hereinafter referred to as the irradiation n / γ ratio).

  First, the void ratio previously stored in the void ratio storage means 42b in association with the void ratio with respect to the ratio of the neutron flux and the gamma ray flux that passes through the void and irradiates the LPRM (hereinafter referred to as the irradiation n / γ ratio). Remember the data.

  Further, the DC component neutron sensitivity and DC component gamma ray sensitivity of each LPRM are recorded in advance in the sensitivity storage means 42a.

  The detector characteristic determination unit 11e of the lifetime determination apparatus 10 gives the neutron component and the gamma ray component in the direct current component to the irradiation n / γ ratio calculation unit 41a.

  The irradiation n / γ ratio calculation means 41a receives the neutron component and the gamma ray component in the DC component of each LPRM from the detector characteristic determination means 11e. Further, the irradiation n / γ ratio calculating unit 41 a reads the DC component neutron sensitivity and DC component gamma ray sensitivity of each LPRM from the sensitivity storage unit 42. Subsequently, the irradiation n / γ ratio calculating means 41a divides the neutron component by the neutron sensitivity to neutron flux value irradiated to the LPRM, and the gamma ray component by gamma ray sensitivity to irradiate each LPRM. Each bundle value is obtained.

  Subsequently, the irradiation n / γ ratio calculating means 41a obtains the irradiation n / γ ratio by dividing the neutron flux value by the gamma ray flux value. Subsequently, the irradiation n / γ ratio calculation means 41a gives this irradiation n / γ ratio to the peripheral void ratio evaluation means 41b.

  Subsequently, the peripheral void ratio evaluation means 41b searches the irradiation n / γ ratio received from the irradiation n / γ ratio calculation means 41a according to the void ratio storage means 42b, and acquires the void ratio corresponding to this ratio. Subsequently, the peripheral void ratio evaluation means 41 b gives the value of the void ratio in water around each LPRM to the core performance calculation means 31.

  Subsequently, the core performance calculation means 31 receives the value of the void ratio around each LPRM from the peripheral void ratio evaluation means 41b, and performs the core performance calculation based on the void ratio value, whereby the neutron flux distribution in the core is calculated. Ask for. Further, the core performance calculation means 31 obtains the neutron flux at the insertion position of each LPRM from this distribution, obtains the value of the accumulated neutron flux irradiated to each LPRM by accumulating the value of this neutron flux, The bundle value is written in the accumulated neutron flux history storage means 12c in the storage means 12.

  According to the reactor core monitoring device 20, the neutron component value and the gamma ray component value in the DC component that can be separated by using the measurement history can be used by using the life determination device 10. By using the neutron component value and the gamma ray component value, the neutron distribution correcting means 40 can determine an accurate irradiation n / γ ratio for each neutron detector. If a neutron detector is inserted in the entire core, an accurate distribution of the ratio of neutron flux and gamma ray flux in the core (hereinafter referred to as core n / γ ratio distribution) is obtained from this irradiation n / γ ratio. It becomes possible.

  Moreover, according to this reactor core monitoring apparatus 20, the void ratio around each neutron detector can be obtained using the irradiation n / γ ratio of each neutron detector.

  The void ratio is used to correct for voids when calculating the neutron flux distribution in the core in the core performance calculation.

  Conventionally, a value predicted in advance has been used as the void ratio. For this reason, when applied to a practical furnace during operation, it was difficult to cope with changes in the void ratio.

  According to the reactor core monitoring device 20, the void ratio around each neutron detector can be obtained from the measurement result. Therefore, by calculating the core performance using the void ratio obtained by this actual measurement, a more accurate and accurate neutron flux distribution in the core can be obtained.

  In addition, by utilizing this accurate core neutron flux distribution for reactor power monitoring, improvement in reactor core monitoring performance can be expected.

  Even if 10A or 10B is used instead of the lifetime determining apparatus 10 shown in FIG. 1 as the lifetime determining apparatus 10 used in the reactor core monitoring apparatus 20, it is possible to achieve the same operational effects. .

  Further, the nuclear lifetime determining means 11f of the lifetime determining device 10 or the lifetime determining device 10A, or the nuclear lifetime determining means 10f of the lifetime determining device 10B, the detector dose evaluation means 11g, the structural lifetime determining means 11h, and the detector lifetime. The determination unit 11i is not necessary in the present embodiment, and may be omitted.

[Fifth Embodiment]
FIG. 16 is an overall configuration diagram showing a fifth embodiment of the lifetime determining device for a neutron detector according to the present invention.

  The reactor core monitoring apparatus 20A using the neutron detector lifetime determination apparatus 10 shown in this embodiment is capable of performing highly accurate reactor power monitoring using the in-core gamma ray flux distribution. In this embodiment, the function of the neutron flux distribution correcting means 40 is different from the reactor core monitoring apparatus 20 shown in FIG. Since other configurations and operations are not substantially different from the reactor core monitoring apparatus 20 shown in FIG. 15, the same components are denoted by the same reference numerals and description thereof is omitted.

  The calculation means 41 is configured by reading a program into a computer or a required circuit, and functions as an irradiation n / γ ratio calculation means 41a and a gamma ray output distribution correction means 41c, and is further connected to a storage means 42. . The calculation means 41 has a function of reading data in the storage means 42 as necessary.

  The storage means 42 is computer-readable and has a function of recording the sensitivity storage means 42a.

  The irradiation n / γ ratio calculation means 41a receives the DC component history and fluctuation component history of each LPRM received from the detector characteristic determination means 11e, and the DC component neutron sensitivity and gamma ray of each LPRM read from the sensitivity storage means 42a. Using the sensitivity, it has a function of obtaining the irradiation n / γ ratio of each LPRM. Further, the irradiation n / γ ratio calculating means 41a has a function of giving this irradiation n / γ ratio to the gamma ray output distribution correcting means 41c.

  The gamma ray output distribution correcting means 41c is configured to evaluate the irradiation n / γ ratio of each LPRM from the irradiation n / γ ratio calculating means 41a, and the in-core gamma ray flux distribution from a means (not shown) for evaluating the gamma ray flux distribution from the gamma ray detector output. Has the function to receive. Further, the gamma ray output distribution correcting means 41c obtains the in-core n / γ ratio distribution from the irradiation n / γ ratio of each LPRM, and multiplies the in-core n / γ ratio distribution and the in-core gamma ray flux distribution to obtain the neutron in the core. It has a function for obtaining a bundle distribution.

  The gamma ray output distribution correcting means 41 c has a function of obtaining the in-core gamma ray flux distribution from the irradiation n / γ ratio of each LPRM and giving this in-core gamma ray flux distribution to the core performance calculating means 31.

  The core performance calculation means 31 corrects the conventional in-core neutron flux distribution calculation result using the in-core gamma ray flux distribution received from the gamma ray power distribution correction means 41c. Further, the core performance calculation means 31 obtains the neutron flux at the insertion position of each LPRM from the corrected distribution of neutron flux in the core, integrates the value of this neutron flux, and the value of the accumulated neutron flux irradiated to each LPRM. And the value of this integrated neutron flux is written into the integrated neutron flux history storage means 12c in the storage means 12.

  Next, the operation of the reactor core monitoring apparatus 20A using the neutron detector lifetime determination apparatus 10 will be described.

  First, a case where a gamma ray detector is used for monitoring the reactor power using the gamma ray flux distribution in the core will be described.

  When monitoring the power distribution of a nuclear reactor, a gamma ray detector such as a γ thermometer may be used. Monitoring of the reactor power distribution (neutron flux distribution) using this gamma ray detector is generally performed by obtaining the in-core neutron flux distribution by the following procedure.

  First, the gamma ray flux distribution in the core is obtained from the output of the gamma ray detector inserted in the entire core. Next, this in-core gamma ray flux distribution is multiplied by the in-core n / γ ratio distribution calculated by the core performance calculation.

  In conventional reactor power monitoring, reactor power distribution monitoring is performed using the neutron flux distribution in the core obtained as a result.

  In this embodiment, the n / γ ratio distribution in the core is not the distribution calculated by the core performance calculation, but the irradiation n / γ ratio of each neutron detector, and the n / γ in the core obtained by the following procedure. Apply a ratio distribution.

  First, the gamma ray output distribution correcting means 41c calculates the irradiation n / γ ratio of each LPRM from the irradiation n / γ ratio calculating means 41a, and the in-core gamma ray flux distribution from the means (not shown) for evaluating the gamma ray flux distribution from the gamma ray detector output. , Receive each. Subsequently, the gamma ray output distribution correction unit 41c obtains the n / γ ratio distribution in the core using the irradiation n / γ ratio of each LPRM. Subsequently, the gamma ray output distribution correcting means 41c obtains the in-core neutron flux distribution by multiplying the in-core gamma ray flux distribution by the in-core n / γ ratio distribution.

  Since this reactor core monitoring device 20A uses the life determination device 10, it can use the neutron component value and the gamma ray component value in the DC component that can be separated by using the measurement history. By using the neutron component value and the gamma ray component value, the neutron distribution correcting means 40 can determine an accurate irradiation n / γ ratio for each neutron detector. The in-core neutron flux distribution can be obtained from the output of the gamma ray detector using the in-core n / γ ratio distribution obtained by using this irradiation n / γ ratio.

  The in-core n / γ ratio distribution obtained by using the irradiation n / γ ratio of each LPRM is obtained based on actual measurement, and is more accurate than the in-core n / γ ratio distribution obtained by the core performance calculation.

  For this reason, when obtaining the neutron flux distribution in the core by using the gamma ray detector by the reactor core monitoring apparatus 20A, a more accurate distribution can be obtained as compared with the conventional case. Therefore, reactor power distribution monitoring using a gamma ray detector can be performed with high accuracy.

  Next, the case of correcting the in-core neutron flux distribution obtained by the core performance calculation when performing reactor power monitoring using the in-core gamma ray flux distribution will be described.

  The gamma ray output distribution correction means 41 c obtains the in-core gamma ray flux distribution from the irradiation n / γ ratio of each LPRM received from the irradiation n / γ ratio calculation means 41 a and gives this in-core gamma ray flux distribution to the core performance calculation means 31. .

  Next, the core performance calculation means 31 receives the in-core gamma ray flux distribution from the gamma ray output distribution correction means 41c. Subsequently, the core performance calculation means 31 applies the in-core gamma ray flux distribution to the in-core neutron flux distribution obtained by the core performance calculation to correct the in-core neutron flux distribution. Further, the core performance calculation means 31 obtains the neutron flux at the insertion position of each LPRM from the corrected distribution of neutron flux in the core, integrates the value of this neutron flux, and the value of the accumulated neutron flux irradiated to each LPRM. And the value of this integrated neutron flux is written into the integrated neutron flux history storage means 12c in the storage means 12.

  According to the reactor core monitoring apparatus 20A, information on the in-core gamma ray flux distribution can be added to the conventional core performance calculation of the in-core neutron flux distribution, and an accurate in-core neutron flux distribution can be configured. Therefore, by utilizing this accurate core neutron flux distribution for reactor power monitoring, it is expected to improve the core monitoring performance of the reactor.

  In addition, even if 10A or 10B is used instead of the lifetime determination apparatus 10 shown in FIG. 1 as the lifetime determination apparatus 10 used in the reactor core monitoring apparatus 20A, it is possible to achieve an equivalent effect. .

  Further, the nuclear lifetime determining means 11f of the lifetime determining device 10 or the lifetime determining device 10A, or the nuclear lifetime determining means 10f of the lifetime determining device 10B, the detector dose evaluation means 11g, the structural lifetime determining means 11h, and the detector lifetime. The determination unit 11i is not necessary in the present embodiment, and may be omitted.

[Sixth Embodiment]
FIG. 17 is an overall configuration diagram showing a sixth embodiment of the lifetime determining apparatus for a neutron detector according to the present invention.

  The reactor core monitoring apparatus 20B using the neutron detector lifetime determination apparatus 10 shown in this embodiment can evaluate the self-absorption amount of neutrons by the neutron detector. In this embodiment, the function of the neutron distribution correction means 40 is different from the reactor core monitoring apparatus 20 shown in FIG. Since other configurations and operations are not substantially different from the reactor core monitoring apparatus 20 shown in FIG. 15, the same components are denoted by the same reference numerals and description thereof is omitted.

  The calculation means 41 is configured by reading a program into a computer or a required circuit, and functions as an irradiation n / γ ratio calculation means 41a and a neutron self-absorption correction means 41d, and is further connected to a storage means 42. The The calculation means 41 has a function of reading data in the storage means 42 as necessary.

  The storage means 42 is computer readable and has a function of recording the sensitivity storage means 42a and the self-absorption amount storage means 42c.

  The irradiation n / γ ratio calculation means 41a receives the DC component history and fluctuation component history of each LPRM received from the detector characteristic determination means 11e, and the DC component neutron sensitivity and gamma ray of each LPRM read from the sensitivity storage means 42a. Using the sensitivity, it has a function of obtaining the irradiation n / γ ratio of each LPRM. The irradiation n / γ ratio calculating means 41a has a function of giving this irradiation n / γ ratio to the neutron self-absorption correcting means 41d.

  The neutron self-absorption correction means 41d searches the irradiation n / γ ratio of each LPRM received from the irradiation n / γ ratio calculation means according to the self-absorption storage means 42c, and acquires the self-absorption amount corresponding to this ratio. Has the function of The neutron self-absorption correcting means 41 d has a function of giving the self-absorption amount of each LPRM to the core performance calculating means 31.

  The core performance calculation means 31 receives the self-absorption amount of each LPRM from the neutron flux distribution correction means 40, and calculates the core performance calculation taking the self-absorption amount into consideration, thereby obtaining the in-core neutron flux distribution of the reactor. It has a function. Further, the core performance calculation means 31 obtains the neutron flux at the insertion position of each LPRM from this distribution, obtains the value of the accumulated neutron flux irradiated to each LPRM by accumulating the value of this neutron flux, It has a function of writing the value of the bundle into the integrated neutron flux history storage means 12c in the storage means 12.

  Next, the operation of the reactor core monitoring apparatus 20B using the neutron detector lifetime determination apparatus 10 will be described.

  Neutrons and gamma rays are absorbed primarily by the LPRM structural material as it passes through the LPRM. The absorption rate by this LPRM differs between neutrons and gamma rays. Therefore, the amount of neutron self-absorption by LPRM can be related to the irradiation n / γ ratio of LPRM.

  First, the self-absorption amount storage means 42c stores in advance self-absorption amount data in which the neutron self-absorption amount by LPRM is associated with the irradiation n / γ ratio of LPRM and stored.

  The neutron self-absorption correction means 41d searches the irradiation n / γ ratio received from the irradiation n / γ ratio calculation means 41a according to the self-absorption amount storage means 42c, and acquires the self-absorption amount corresponding to this ratio. Subsequently, the neutron self-absorption correction means 41 d gives the neutron self-absorption amount of each LPRM to the core performance calculation means 31.

  Subsequently, the core performance calculation means 31 calculates the core performance by using the neutron self-absorption amount of each LPRM to obtain the neutron flux distribution in the core. Further, the core performance calculation means 31 obtains the neutron flux at the insertion position of each LPRM from this distribution, obtains the value of the accumulated neutron flux irradiated to each LPRM by accumulating the value of this neutron flux, The bundle value is written in the accumulated neutron flux history storage means 12c in the storage means 12.

  By the above procedure, the neutron self-absorption amount by each LPRM can be obtained using the irradiation n / γ ratio of each LPRM.

  The self-absorption amount is used for correcting the neutron self-absorption by the neutron detector when obtaining the neutron flux distribution in the core by the core performance calculation.

  Conventionally, this self-absorption amount is handled assuming a constant value in the core performance calculation. However, in a practical reactor in operation, this self-absorption amount is not a constant value, and changes as the irradiation n / γ ratio of each neutron detector changes.

  According to the reactor core monitoring device 20B, the neutron self-absorption amount of each neutron detector can be evaluated based on the accurate irradiation n / γ ratio obtained by using the measurement history of the lifetime determination device 10. it can. For this reason, even when the irradiation n / γ ratio of the neutron detector changes, such as when the void ratio or neutron spectrum changes, the self-absorption amount corresponding to this change can be evaluated. By using this self-absorption amount, it is possible to accurately correct neutron self-absorption by the neutron detector, and to perform highly accurate core performance calculation.

  Moreover, by using this highly accurate core performance calculation for reactor power monitoring, it is expected to improve the core monitoring performance of the reactor.

  It should be noted that the same effect can be obtained by using another life determination device 10A or 10B instead of the life determination device 10 shown in FIG. 1 as the life determination device 10 used in the reactor core monitoring device 20B. It is possible.

  Further, the nuclear lifetime determining means 11f of the lifetime determining device 10 or the lifetime determining device 10A, or the nuclear lifetime determining means 10f of the lifetime determining device 10B, the detector dose evaluation means 11g, the structural lifetime determining means 11h, and the detector lifetime. The determination unit 11i is not necessary in the present embodiment, and may be omitted.

[Seventh Embodiment]
FIG. 18 is an overall configuration diagram showing a seventh embodiment of the lifetime determining apparatus for a neutron detector according to the present invention.

  The reactor core monitoring device 20C using the neutron detector lifetime determination device 10 shown in this embodiment is configured to be able to monitor the overlap region between the activation region neutron detector and the LPRM. In this embodiment, the life determination device 10 has the same effects as the life determination device 10 shown in FIG. Therefore, in the description of the reactor core monitoring device 20, the same configurations and operations as those of the life determination device 10 are denoted by the same reference numerals and description thereof is omitted.

  The reactor core monitoring device 20C includes a life determination device 10, an LPRM group 21, an SRNM 21z, a multiplexer 22, a core performance calculation unit 31, and an overlap region evaluation unit 34.

  The reactor core monitoring device 20 </ b> C has a structure in which two life determination devices 10 are connected via one overlap region evaluation means 34.

  One life determination device 10 is connected to the LPRM group 21 via the multiplexer 22 and also connected to the core performance calculation means 31.

  The other life determination device 10 is connected to a start-up region neutron monitor (SRNM) 21 z and also connected to the core performance calculation means 31.

  SRNM is generally a neutron detector that measures the neutron flux distribution in the core during reactor shutdown and during low power operation.

  The LPRM group 21 side life determination device 10 and the SRNM 21 z side life determination device 10 are both connected to the overlap evaluation means 34.

  Note that the number of life determination devices 10 is not necessarily two, and the life determination device 10 may be used according to the number of LPRM groups 21 and according to the number of SRNMs 21z. In any case, it should be noted that all the life judging devices 10 are connected to one overlap evaluating means 34 in order to compare their outputs.

  The detector characteristic determination unit 11e has a function of giving the corrected DC component value received from the DC component correction unit 11c and the corrected fluctuation component value received from the fluctuation component correction unit 11d to the overlap region evaluation unit 34. .

  The overlap region evaluation means 34 includes the corrected DC component value and fluctuation component value of the LPRM output received from the lifetime determination device 10 on the LPRM group 21 side, and the corrected SRNM output received from the lifetime determination device 10 on the SRNM 21z side. The DC component value and the fluctuation component value are compared, and the LPRM output and the SRNM output overlap abnormality is detected. The overlap region evaluation means 34 has a function of displaying the detected abnormality on a display (not shown) when an abnormality in overlap between the LPRM output and the SRNM output is detected in advance.

  Next, the operation of the reactor core monitoring device 20C using the neutron detector lifetime determination device 10 will be described.

  FIG. 19A is an explanatory diagram showing a comparison between the LPRM output and the SRNM output when the reactor is stopped. Since the LPRM output and the SRNM output have different scales, the LPRM output or the SRNM output is appropriately enlarged or reduced in FIG. 19A so that the relative comparison can be made by plotting in one graph.

  For example, if there is an abnormality in the SRNM output, the monitoring range of LPRM and SRNM (the linear region in FIG. 19A) will not overlap (do not overlap) if the reactor output is reduced to stop the operating reactor. )there is a possibility. In this case, even if only one SRNM is abnormal, an abnormal signal is output.

  In order to avoid this harmful effect due to the abnormal signal output, it is only necessary to detect the SRNM abnormality before the reactor power enters the overlap region. For this purpose, the history of the direct current component and the fluctuation component of the SRNM output is monitored.

  The monitoring of SRNM is generally performed by monitoring the fluctuation component value. When there is an abnormality in the SRNM output, if the history of the fluctuation component of the SRNM output is monitored, as shown in FIG. 19 (a), during normal operation before the reactor output is reduced (the SRNM output is a constant value). Even when), an abnormality can be detected.

  Therefore, when stopping the reactor, in order to detect an abnormality of SRNM before reaching the overlap region, the history of the SRNM output is evaluated before or immediately after the start of the decrease.

  The overlap region evaluation unit 34 calculates the corrected DC component value and fluctuation component value of the LPRM output from the lifetime determination device 10 on the LPRM group 21 side, and the corrected DC component value of the SRNM output from the lifetime determination device 10 on the SRNM 21z side. And the fluctuation component value are received.

  The overlap region evaluation means 34 evaluates the fluctuation component value history of the SRNM output before the reactor power decrease or immediately after the start of the decrease. When there is an abnormality as compared with the fluctuation component value in the normal state, the overlap region evaluation means 34 displays an indication notifying that an abnormality has been detected on a display (not shown).

  The overlap region evaluation means 34 evaluates the ratio of the SRNM output to the DC component value of the fluctuation component value before or immediately after the decrease in the reactor output. When this ratio is abnormal as compared with the normal time, the overlap area evaluation means 34 displays an indication notifying that an abnormality has been detected on a display (not shown).

  The ratio of the fluctuation component of the SRNM output to the DC component is proportional to the charge per SRNM output pulse. Therefore, this change in ratio suggests a change in SRNM characteristics. Therefore, in detecting the abnormality of SRNM, the evaluation of this ratio is supplementarily used in addition to the fluctuation component value history evaluation.

  According to the reactor core monitoring apparatus 20C, the history of the SRNM output can be monitored by using the life determination apparatus 10. By monitoring this history, when stopping the reactor, it is possible to detect an abnormality in the SRNM output before or immediately after the decrease in the reactor output. Therefore, before reaching the overlap region, it is possible to take appropriate measures such as repairing the SRNM with an output abnormality or bypassing the SRNM, and it is possible to eliminate an inadvertent abnormality signal output. .

  FIG. 19B is an explanatory diagram showing a comparison between the LPRM output and the SRNM output when the nuclear reactor is started. Since the LPRM output and the SRNM output are different in scale, the LPRM output or the SRNM output is appropriately enlarged or reduced in FIG. 19B so that the relative comparison can be made by plotting in one graph.

  For example, when LPRM has an abnormality, the monitoring range of LPRM and SRNM may not overlap if a reactor that is stopped is started. In this case, even if only one LPRM is abnormal, an abnormal signal is output.

  In order to avoid the harmful effects caused by the abnormal signal output, the LPRM abnormality may be detected at a stage before the reactor output enters the overlap region. For this purpose, the history of the DC component and fluctuation component of the LPRM output is monitored.

  Since the fluctuation component of the LPRM output is hardly affected by gamma rays, it has a characteristic that the output is linear with respect to the reactor output at an early stage after the reactor startup compared to the DC component. By utilizing this feature, abnormality detection of LPRM output is performed. If the LPRM output has an abnormality, if the history of the fluctuation component of the LPRM output is monitored, as shown in FIG. Can do.

  The overlap region evaluation unit 34 calculates the corrected DC component value and fluctuation component value of the LPRM output from the lifetime determination device 10 on the LPRM group 21 side, and the corrected DC component value of the SRNM output from the lifetime determination device 10 on the SRNM 21z side. And the fluctuation component value are received.

  The overlap region evaluation means 34 evaluates the fluctuation component value history of the LPRM output immediately after the reactor is started. When there is an abnormality in the rise of the fluctuation component, the overlap area evaluation means 34 displays a notification notifying that an abnormality has been detected on a display (not shown).

  The reactor core monitoring device 20C can monitor the history of LPRM output by using the life determination device 10. For this reason, by using this history, when starting the nuclear reactor, it is possible to detect an abnormality in the LPRM output immediately after starting the nuclear reactor. Therefore, before reaching the overlap region, it is possible to take appropriate measures such as repairing an LPRM having an output abnormality or bypassing the LPRM, and an inadvertent abnormality signal output can be eliminated. .

  Even if 10A or 10B is used instead of the life determination device 10 shown in FIG. 1 as the life determination device 10 used in the reactor core monitoring device 20C, it is possible to achieve the same effect. .

  Further, the nuclear lifetime determining means 11f of the lifetime determining device 10 or the lifetime determining device 10A, or the nuclear lifetime determining means 10f of the lifetime determining device 10B, the detector dose evaluation means 11g, the structural lifetime determining means 11h, and the detector lifetime. The determination unit 11i is not necessary in the present embodiment, and may be omitted.

  The first to seventh embodiments may be implemented by selecting and combining any number of embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram which shows 1st Embodiment of the lifetime determination apparatus of the neutron detector which concerns on this invention. Explanatory drawing which shows the relationship between the integration | stacking neutron flux irradiated to LPRM, and the DC component value of LPRM output. (A) is explanatory drawing which shows the relationship between the integration neutron flux irradiated to LPRM at the time of gas leak, and the DC component value of LPRM output, (b) is the integration neutron flux irradiated to LPRM, and after correction | amendment FIG. 4C is an explanatory diagram showing the relationship between the fluctuation component value of the LPRM output of FIG. 5C, and FIG. 5C is a diagram illustrating the accumulated neutron flux irradiated to the LPRM and the neutron component in the DC component of the corrected LPRM output when Method 1 is applied; Explanatory drawing which shows the relationship with a gamma ray component. Explanatory drawing which shows the relationship between the integration | stacking neutron flux irradiated to LPRM in the case of applying Method 2, and the neutron component and gamma ray component in the direct current | flow component of LPRM output after correction | amendment. (A) is an explanatory diagram showing the LPRM applied voltage characteristic of the fluctuation component of the LPRM output, and (b) shows the LPRM applied voltage characteristic of the fluctuation component of the LPRM output when the slope of the characteristic curve at the drive voltage is larger than (a). FIG. Explanatory drawing which shows the LPRM applied voltage characteristic of the fluctuation component of LPRM output when there is noise induction in the neutron detector output. (A) is explanatory drawing which shows the frequency characteristic of fluctuation component of LPRM output, (b) is explanatory drawing which shows the frequency characteristic of fluctuation component when the fluctuation component neutron sensitivity of LPRM changes. (A) is a flowchart which shows the procedure which evaluates the fluctuation | variation component attenuation amount by a facility cable, (b) is explanatory drawing which shows the signal attenuation data of a laying cable. The whole block diagram which shows 2nd Embodiment of the lifetime determination apparatus of the neutron detector which concerns on this invention. (A) is an explanatory diagram showing a relative comparison of the time response of the DC component and fluctuation component of the LPRM output, and (b) is the integrated neutron flux irradiated to the LPRM and the prompt component and the delayed component of the DC component of the LPRM output. Explanatory drawing which shows the relationship. The whole block diagram which shows 3rd Embodiment of the lifetime determination apparatus of the neutron detector which concerns on this invention. The figure which shows the structure of the detector lifetime determination apparatus of the lifetime determination apparatus of the neutron detector shown in FIG. The flowchart which shows the procedure at the time of performing nuclear lifetime determination and structural lifetime determination required in the lifetime determination of a neutron detector by the lifetime determination apparatus of the neutron detector which concerns on this invention. The flowchart which shows the procedure at the time of performing the lifetime determination of a neutron detector by the lifetime determination apparatus of the neutron detector which concerns on this invention, and showing the neutron detector determined as the lifetime The whole block diagram which shows 4th Embodiment of the lifetime determination apparatus of the neutron detector which concerns on this invention. The whole block diagram which shows 5th Embodiment of the lifetime determination apparatus of the neutron detector which concerns on this invention. The whole block diagram which shows 6th Embodiment of the lifetime determination apparatus of the neutron detector which concerns on this invention. The whole block diagram which shows 7th Embodiment of the lifetime determination apparatus of the neutron detector which concerns on this invention. (A) is explanatory drawing which compared and showed the LPRM output and SRNM output in the case of stopping a nuclear reactor, (b) is the explanatory drawing which compared and showed the LPRM output and SRNM output in the case of starting a nuclear reactor.

Explanation of symbols

10, 10A, 10B Lifetime determination device 11 Calculation means 11a DC component measurement means 11b Fluctuation component measurement means 11c DC component correction means 11d Fluctuation component correction means 11e Detector characteristic determination means 11f Nuclear lifetime determination means 11g Detector irradiation amount evaluation means 11h Structural life determination means 11i Detector life determination means 11i1 Next regular inspection irradiation dose evaluation means 11i2 Next regular inspection life determination means 11i3 Next periodic inspection irradiation dose evaluation means 11i4 Next periodic inspection life determination means 11i5 Replacement detector presenting means 12 Storage Means 12a DC component history storage means 12b Fluctuation component history storage means 12c Accumulated neutron flux history storage means 12d Applied voltage history storage means 12e Frequency characteristic history storage means 12f Constant storage means 12g Gas μ storage means 12h Gas μ correction fluctuation history storage Means 12i Elapsed time history record It means 12j next periodic inspection during refueling plan storage unit 20, 20A, 20B, 20C nuclear reactor core monitoring system 21 LPRM group 21a, 21b, 21c, 21d LPRM
21z SRNM
22 multiplexer 31 core performance calculation means 32 control rod operation information acquisition means 33 elapsed time provision means 34 overlap region evaluation means 40 neutron flux distribution correction means 41 calculation means 41a irradiation n / γ ratio calculation means 41b peripheral void ratio evaluation means 41c gamma rays Output distribution correction means 41d Self absorption amount correction means 42 Storage means 42a Sensitivity storage means 42b Void rate storage means 42c Self absorption amount storage means

Claims (21)

DC component measuring means for measuring the DC component in the electrical signal output from the radiation detecting means inserted in the nuclear reactor,
DC component history storage means for storing the measured value of the DC component as a history;
DC component correction means for reading the history of the DC component measurement value from the DC component history storage means and correcting the history;
Fluctuation component measuring means for measuring a fluctuation component in the electrical signal;
Fluctuation component history storage means for storing the measured value of the fluctuation component as a history;
A lifetime determination apparatus for a neutron detector, comprising: fluctuation component correction means for reading the fluctuation component measured value history from the fluctuation component history storage means and correcting the history. Constant storage means for storing the sensitivity ratio of the DC component neutron sensitivity to the fluctuation component neutron sensitivity of the radiation detection means inserted in the reactor in advance,
DC component measuring means for measuring a DC component in an electrical signal output from the radiation detecting means;
DC component history storage means for storing the measured value of the DC component as a history;
DC component correction means for reading the history of the DC component measurement value from the DC component history storage means, and extracting and correcting sudden changes in the DC component measurement value from the history;
Fluctuation component measuring means for measuring a fluctuation component in the electrical signal;
Fluctuation component history storage means for storing the measured value of the fluctuation component as a history;
Fluctuation component correction means for correcting the fluctuation component history read from the fluctuation component history storage means based on the data of the sudden change received from the DC component correction means;
Detector characteristic determining means for determining the neutron component in the corrected DC component by multiplying the corrected fluctuation component by the sensitivity ratio read from the constant storage means,
The detector characteristic determining means is configured to be able to separate the corrected DC component into a neutron component and a gamma ray component by comparing the corrected DC component based on the measurement value history and the neutron component. A device for determining the lifetime of a neutron detector. The constant storage means is a constant storage means that stores in advance the nuclear life ratio and the sensitivity ratio,
Nuclei for determining the end of the nuclear life of the radiation detection means when the ratio obtained by dividing the corrected neutron component in the DC component by the gamma ray component is equal to or less than the nuclear life ratio read from the constant storage means The lifetime determination apparatus for a neutron detector according to claim 2, further comprising a static lifetime determination means. The sensitivity ratio stored in the constant storage means is obtained by subtracting the gamma ray component in the DC component determined by the design specification of the radiation detection means from the DC component at the time of initial installation of the reactor of the radiation detection means. The lifetime determination apparatus of the neutron detector of Claim 2 or 3 obtained by remove | dividing the neutron component in the direct current | flow component of time by the fluctuation component at the time of the said first installation. The sensitivity ratio stored in the constant storage means was measured by measuring the output of a pair of the radiation detection means having the same structure and different only in the presence or absence of neutron sensitive substances under the same irradiation conditions before inserting the reactor. The neutron component in the direct current component obtained by subtracting the direct current component of the radiation detection means having no neutron sensitive material from the direct current component of the radiation detection means having the sensitive material is changed as a fluctuation component of the radiation detection means having the neutron sensitive material. The lifetime determination apparatus for a neutron detector according to claim 2 or 3, wherein the lifetime determination apparatus is obtained by dividing by. The constant storage means is a constant storage means that further stores in advance the sensitivity ratio and the electron mobility of the gas of the radiation detection means serving as a reference,
Gas μ storage means for storing in advance the electron mobility of the gas of the radiation detection means in association with the slope of the applied voltage characteristic curve of the fluctuation component of the radiation detection means;
An applied voltage history storage means for changing an applied voltage to the radiation detecting means and storing the applied voltage value as a history;
A fluctuation component history storage unit for gas μ correction that stores, as a history, a fluctuation component value when the fluctuation component measurement unit measures an applied voltage to the radiation detection unit;
The fluctuation component correction means reads data from the gas μ correction fluctuation component history storage means and the applied voltage history storage means, obtains an inclination of an applied voltage characteristic curve of the fluctuation component, and based on the inclination, the gas Find the μ storing means extracts the electron mobility of the corresponding gas, based on the ratio of the electron mobility of the gas serving as the reference read and the electron mobility of the extracted gas from the constant storing unit The lifetime determination apparatus for a neutron detector according to claim 2 or 3, wherein the fluctuation component history after correction is configured to be corrected. The constant storage means is a constant storage means further storing the fluctuation component value measured by the fluctuation component measurement means as a noise component value with the sensitivity ratio and the voltage applied to the radiation detection means being 0V,
4. The lifetime determination device for a neutron detector according to claim 2, wherein the fluctuation component correction unit is configured to be able to perform correction by subtracting the noise component value read from the constant storage unit from the corrected fluctuation component value. 5. . A frequency characteristic history storage means for storing the frequency characteristics of the radiation detection means as a reference in advance;
The fluctuation component correction means measures the frequency characteristic of the fluctuation component of the radiation detection means, performs spectral analysis of the frequency characteristic and the reference frequency characteristic read from the frequency characteristic history storage means, and compares them. The lifetime determination apparatus for a neutron detector according to claim 2 or 3, wherein a relative change ratio of the neutron sensitivity of the fluctuation component is obtained, and the fluctuation component history after the correction can be corrected based on the change ratio. 4. The neutron detection according to claim 2, wherein the fluctuation component correction unit further has a function of considering an attenuation amount of the fluctuation component due to a laying cable of the radiation detection unit when correcting the fluctuation component history. 5. Equipment life assessment device. An elapsed time providing means for obtaining an elapsed time calculated from the control rod operation time;
Elapsed time history storage means for receiving the elapsed time of the previous period from the elapsed time providing means and storing the history of the elapsed time,
The DC component correcting means is configured to create data corresponding to the corrected DC component history with respect to the elapsed time history and to provide the data to the detector characteristic determining means,
The fluctuation component correction unit is configured to create data in which the corrected fluctuation component history is associated with the elapsed time history and provide the data to the detector characteristic determination unit.
The detector characteristic determining means obtains the corrected DC component value at an elapsed time when the corrected fluctuation component history is substantially constant and an elapsed time when the corrected DC component history is substantially constant. The difference is obtained, and the corrected DC component is configured to be separable into a component composed of an immediate component and a neutron component of the gamma ray component and a component composed of a delayed component of the gamma ray component. Lifetime detector for neutron detectors. The constant storage means is a constant storage means further storing a structural lifetime irradiation amount in advance,
By dividing the neutron component in the corrected direct current component received from the detector characteristic determining means by the thermal neutron flux irradiated by the radiation detecting means, the direct current component neutron sensitivity of the radiation detecting means is obtained. Obtaining and accumulating the thermal neutron flux irradiated by the radiation detecting means from the change in the sensitivity of the DC component neutrons, and receiving the radiation detecting means container from the integrated value of the thermal neutron flux Detector dose determination means for calculating the cumulative dose of fast neutrons;
A structural lifetime determination means for determining that the structural lifetime of the radiation detection means is over, by the cumulative irradiation dose of the fast neutrons being equal to or greater than the structural lifetime dose stored in the constant storage means in advance;
The detector further comprises detector life determination means that receives the determination results of the nuclear life determination means and the structural life determination means, and determines that the life of the radiation detection means is ended when one of them is determined to be life. Item 3. The lifetime determination device for a neutron detector according to Item 3. The detector lifetime determination means predicts the neutron flux irradiated to the previous radiation detection means between the present and the next periodic inspection based on the neutron flux currently being irradiated by the radiation detection means. A next regular inspection dose evaluation means for predicting an integrated neutron flux for each LPRM at the start of the next periodic inspection,
At the start of the next periodic inspection in the previous period by correcting the ratio obtained by dividing the neutron component in the corrected DC component by the gamma ray component with the predicted value of the integrated neutron flux for the previous period radiation detector at the start of the next periodic inspection. Predicting the ratio of the neutron component in the direct current component of the radiation detector divided by the gamma ray component in the above, and comparing the predicted ratio with the nuclear lifetime ratio read from the constant constant storage means, It is determined whether or not the nuclear life of the radiation detection means ends at the start of the inspection, and the accumulated dose of fast neutrons irradiated by the container of the radiation detection means is determined as the initial radiation at the start of the next periodic inspection. By correcting with the predicted value of the integrated neutron flux for the detector, the container of the radiation detection means is irradiated at the start of the next periodic inspection in the previous period. By predicting the cumulative dose of fast neutrons received, and comparing the predicted cumulative dose of fast neutrons with the structural lifetime dose stored in the constant storage means, the next periodic inspection is started. In the next periodic inspection life determination means for determining whether the structural life of the radiation detection means is completed in
Based on the predicted value of the neutron flux irradiated by the radiation detection means at the start of the next periodic inspection obtained from the neutron flux irradiated by the current radiation detection means and the fuel condition, the periodic inspection is performed one after the next. Predicting the neutron flux irradiated to the radiation detection means during the previous period, predicting the accumulated neutron flux for each LPRM at the start of the next periodic inspection,
The ratio obtained by dividing the corrected neutron component in the DC component by the gamma ray component is corrected by the predicted value of the integrated neutron flux for the previous radiation detector at the start of the next periodic inspection, thereby starting the next periodic inspection. Predicting a ratio obtained by dividing the neutron component in the direct current component of the radiation detector by a gamma ray component, and comparing the predicted ratio with the nuclear life ratio read from the initial constant storage means, It is determined whether or not the nuclear life of the radiation detecting means ends at the start of the inspection, and the accumulated dose of fast neutrons irradiated by the container of the radiation detecting means is determined as the initial radiation at the start of the next periodic inspection. By correcting with the predicted value of the integrated neutron flux for the detector, the radiation detection means can be stored at the start of the next periodic inspection. By predicting the cumulative dose of fast neutrons irradiated by the vessel, and comparing the predicted cumulative dose of fast neutrons with the structural lifetime dose stored in the constant storage means, One after another regular inspection life determination means for determining whether the structural life of the container of the radiation detection means ends at the start of periodic inspection,
It is determined that it is necessary to replace the previous period radiation detection means determined in the next periodical inspection for the nuclear period or the first period container that has reached the structural lifetime between the next periodical inspection and the next periodical inspection. The neutron detector lifetime determination apparatus according to claim 11, further comprising: a replacement detector presenting means for presenting the fact to a user by displaying the information on a display or the like. Measuring a DC component in an electrical signal output from a radiation detection means inserted in the nuclear reactor;
Storing the measured value of the DC component as a history;
Correcting the history of measured values of the DC component;
Measuring a fluctuation component in the electrical signal;
Storing the measured value of the fluctuation component as a history;
Correcting the fluctuation history of the fluctuation component,
A method for determining the lifetime of a neutron detector, comprising: Sensitivity storage means for storing the DC component neutron sensitivity and DC component gamma ray sensitivity of the radiation detection means inserted in the reactor in advance,
DC component measuring means for measuring a DC component in an electrical signal output from the radiation detecting means;
DC component history storage means for storing the measured value of the DC component as a history;
DC component correction means that reads the history of the DC component measurement value from the DC component history storage means, extracts sudden changes in the DC component measurement value from the history, and corrects the change,
Fluctuation component measuring means for measuring a fluctuation component in the electrical signal;
Fluctuation component history storage means for storing the measured value of the fluctuation component as a history;
Fluctuation component correction means for correcting the fluctuation component history read from the fluctuation component history storage means based on the data of the sudden change received from the DC component correction means;
The neutron flux and the gamma ray flux irradiated to the radiation detection means are obtained by dividing the neutron component and the gamma ray component in the corrected DC component by the DC component neutron sensitivity and the DC component gamma ray sensitivity read from the sensitivity storage means, respectively. And a irradiation neutron flux / gamma ray flux ratio calculating means for calculating a ratio of a neutron flux irradiated to the radiation detecting means and a gamma ray flux. Constant storage means for storing the nuclear life ratio and the sensitivity ratio of the DC component neutron sensitivity of the radiation detection means to the fluctuation component neutron sensitivity in advance;
A detector for multiplying the corrected fluctuation component by the sensitivity ratio read from the constant storage means to obtain a neutron component in the corrected DC component, and separating the corrected DC component into a neutron component and a gamma ray component Characteristic determination means;
Nuclear lifetime that determines the end of the lifetime of the radiation detection means when the ratio obtained by dividing the corrected neutron component in the DC component by the gamma ray component is equal to or less than the nuclear lifetime ratio read from the constant storage means The reactor core monitoring apparatus according to claim 14, further comprising a determination unit. Void ratio storage means for storing the void ratio in association with the neutron flux / gamma ray flux ratio irradiated to the radiation detection means in advance;
Based on the neutron flux / gamma ray flux ratio irradiated to the radiation detecting means received from the irradiated neutron flux / gamma ray flux ratio calculating means, the void ratio storage means is searched to obtain the corresponding void ratio, and this void ratio The reactor core monitoring apparatus according to claim 14, further comprising: a peripheral void ratio evaluation unit that provides a unit for performing a core performance calculation. The irradiation neutron flux / gamma ray flux ratio calculating means receives the neutron flux / gamma flux ratio irradiated to the radiation detection means, and a gamma ray distribution in the core from a gamma ray detector inserted in the reactor, respectively. The reactor core monitoring apparatus according to claim 14 or 15, further comprising a gamma-ray output distribution correcting means for obtaining an in-core neutron flux distribution by multiplying an inner gamma ray flux distribution by the neutron flux / gamma flux ratio. The neutron flux / gamma flux ratio irradiated to the radiation detection means is received from the irradiation neutron flux / gamma flux ratio calculating means, and the gamma ray flux distribution in the core is obtained from the neutron flux / gamma flux ratio, and this gamma ray flux distribution in the core is obtained. The reactor core monitoring apparatus according to claim 14, further comprising a gamma ray power distribution correction unit that supplies the unit to a unit for performing core performance calculation. Self-absorption amount storage means for storing the neutron self-absorption amount by the radiation detection means in association with the neutron flux / gamma ray flux ratio irradiated to the radiation detection means in advance;
Based on the neutron flux / gamma ray flux ratio irradiated to the radiation detecting means received from the irradiated neutron flux / gamma ray flux ratio calculating means, the self-absorption amount storage means is searched to obtain a corresponding self-absorption amount, The reactor core monitoring apparatus according to claim 14, further comprising a neutron self-absorption amount correcting unit that supplies the self-absorption amount to a unit that performs core performance calculation. Constant storage means for storing the sensitivity ratio of the DC component neutron sensitivity to the fluctuation component neutron sensitivity of the radiation detection means inserted in the reactor in advance,
DC component measuring means for measuring a DC component in an electrical signal output from the radiation detecting means;
DC component history storage means for storing the measured value of the DC component as a history;
DC component correction means for reading the history of the DC component measurement value from the DC component history storage means, and extracting and correcting sudden changes in the DC component measurement value from the history;
Fluctuation component measuring means for measuring a fluctuation component in the electrical signal;
Fluctuation component history storage means for storing the measured value of the fluctuation component as a history;
A neutron detector comprising fluctuation component correction means for correcting the fluctuation component history read from the fluctuation component history storage means based on the data of the sudden change received from the DC component correction means. Install multiple life judging devices in parallel,
The number of installed life judging devices is one using a starting area neutron detector as the radiation detecting means and one using a local output area monitor, each one or more,
Monitoring the history of the corrected fluctuation component received from the lifetime determination device on the startup region neutron detector side and the history of the corrected fluctuation component received from the lifetime determination device on the local output region monitor side, Overlap region evaluation to detect anomalies before linearization with respect to reactor power, regarding the output of the startup region neutron detector at the time of shutdown, and the output of the local power region monitor at the time of reactor startup Reactor core monitoring device comprising means. The constant storage means is a constant storage means for storing a nuclear life ratio and the sensitivity ratio in advance.
The lifetime determination apparatus obtains a neutron component in the corrected DC component by multiplying the corrected fluctuation component by the sensitivity ratio read from the constant storage means, and determines the corrected DC component as a neutron component and a gamma ray. Detector characteristic determination means that separates into components;
Nuclear lifetime that determines the end of the lifetime of the radiation detection means when the ratio obtained by dividing the corrected neutron component in the DC component by the gamma ray component is equal to or less than the nuclear lifetime ratio read from the constant storage means The reactor core monitoring apparatus according to claim 20, further comprising a determination unit.

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