JP4393316B2 - Neutron detector lifetime diagnostic system - Google Patents

Description

  The present invention relates to a lifetime diagnosis system for a neutron detector that performs neutron flux level monitoring.

In nuclear power plants, it is important to constantly monitor the power distribution in the reactor for ensuring the safety of the core.
Conventionally, as a means for monitoring the core power of a boiling water reactor, a local power range monitor (LPRM) that monitors local neutron flux levels in the horizontal and axial directions in the reactor ) Is used.

  This local power region monitor calculates the average neutron flux level and heat output of the core from the outputs of multiple neutron detectors (LPRM detectors) placed around the reactor control rods, resulting in an abnormal increase in output. In the event of an accident, the reactor power is monitored by generating an alarm, control rod withdrawal prevention, and generating a reactor scram signal.

  The neutron detector is a nuclear fission ionization chamber that is fixed inside the reactor. The inner surface of the detector is coated with uranium and reacts with neutrons to generate a current. For example, in a 1,100 MWe class boiling water reactor Neutron detectors are loaded in the reactor.

  This neutron detector is subject to neutron irradiation in the furnace for a long period of time, and its output characteristics deteriorate when left reacting. Therefore, it is necessary to perform a timely life diagnosis and to make periodic corrections and replacements.

  In general, the lifetime of a neutron detector that can be used as a guide for replacement includes a nuclear lifetime in which the detection sensitivity deteriorates when irradiated with thermal neutrons, and a service life of the structural materials that make up the neutron detector assembly. Deterioration life diagnosis is performed from the lifespan.

  Regarding the nuclear lifetime of the neutron detector, the actual change in detection sensitivity of the neutron detector is calculated from the detector output signal and used for lifetime diagnosis.

  The neutron detector is a fission ionization chamber as described above, and uranium is applied to the cathode surface of the detector. As the uranium to be applied, in addition to uranium 235 which is a fissile material, uranium which is a fission conversion material. 234 is mixed and applied (for example, refer to Patent Document 1).

  In this case, the mixing ratio of uranium is set to be about uranium 235: uranium 234 = 1: 4.

FIG. 10 shows the change in detection sensitivity accompanying the deterioration of the neutron detector.
In FIG. 10, the vertical axis represents the sensitivity ratio S / S ₀ which is the ratio of the current sensitivity S to the initial sensitivity S ₀ of the neutron detector, and the horizontal axis represents the neutron irradiation amount to the neutron detector.

  Due to the effect of mixing uranium 234, the detection sensitivity of the neutron detector rises first as the neutron irradiation increases (T1) and then gradually decreases (T2) as shown in FIG. At a certain time (T3), the sensitivity ratio L indicating the life limit sensitivity is reached.

In FIG. 10, the sensitivity ratio S / S ₀ of the neutron detector shown on the vertical axis is a calibration current (current required for the neutron detector to show 100%) value I with respect to the initial calibration current value I ₀ of the neutron detector. The ratio I / I ₀ may be regarded as substantially equal. That is,
S / S ₀ ≒ I / I ₀
Holds.

  Therefore, as a life diagnosis of the neutron detector in the conventional local output region monitor, the change in the detection sensitivity is grasped by using the change in the calibration current value I instead of the change in the detection sensitivity S of the neutron detector. , Have a life diagnosis.

  The detected current component of the neutron detector includes a current caused by neutrons and a current caused by other than neutrons. However, the current caused by other than neutrons is usually dominated by gamma rays, and for the sake of simplicity, it will be described as a current caused by gamma rays in the following description.

  In the case of a neutron detector, the detection sensitivity of neutrons is high at the initial stage of the reactor interior loading, and there are many current components due to neutrons. Can no longer be ignored.

  When the ratio of the current component due to gamma rays in the detected current component increases, a response delay of the neutron detector occurs due to the influence of delayed gamma rays.

  Therefore, the point in time at which this response delay is not negligible is set as the nuclear lifetime limit of the neutron detector. That is, the ratio between the current caused by neutrons and the current caused by gamma rays is a factor that determines the nuclear lifetime limit of the neutron detector.

FIG. 11 shows a flowchart of a method for determining the nuclear lifetime of a conventional neutron detector.
As shown in FIG. 11, first, the current calibration current value I of the neutron detector is obtained by the core performance calculation function of the process computer (S201).

Next, using the initial calibration current value _{I 0} obtained in advance as well (S202), calculating the ratio I / _{I 0} of the current calibration current value I with respect to the initial calibration current value _{I 0} (S203).

  This result and the calculated neutron irradiation amount (S204) obtained by the core performance calculation are plotted on a graph to obtain a sensitivity change transition curve of the neutron detector as shown in FIG. 10 (S205).

  The neutron irradiation amount at which the sensitivity change transition curve reaches the sensitivity ratio L indicating the life limit sensitivity is predicted as the life of the neutron detector (S206).

  The update time of the neutron detector is predicted from the predicted lifetime obtained by this method, and the neutron detector update plan is made from the periodic inspection information within the lifetime range (S207).

As described above, as a method of determining the nuclear lifetime of the conventional neutron detector, a method of determining from the degree of decrease in the calibration current value of the neutron detector is used, and generally, in the core performance calculation of the process computer. The lifetime is determined by the ratio of the calibration current value of the obtained neutron detector to the initial value.
Japanese Patent Laid-Open No. 2003-232862

  However, since the conventional neutron detector life diagnosis method evaluates the detection sensitivity from the calibration current value obtained in the core performance calculation, it is affected by the accuracy of the core performance calculation function of the process computer, so accurate life prediction is possible. Difficult to do.

  In addition, since the calibration current is measured by direct current (DC) measurement, the current caused by gamma rays cannot be ignored with respect to the current caused by neutrons as the detection sensitivity deteriorates. Is a value including the influence of gamma rays and the like, and there is a problem that life diagnosis based on highly accurate evaluation cannot be performed.

  When updating the neutron detector based on this life diagnosis result, if it is short even within the accuracy range, it may be updated one cycle earlier than the usable period as a detector, or conversely, if it is long, the usable period If the accuracy of the 47 neutron detectors varies and the periodic inspection period of the power plant is short, the periodic inspection period must be extended to replace the neutron detector. Therefore, there were problems to be solved such as causing economic loss.

  The present invention has been made to solve the above-described problems, and can appropriately and accurately perform life diagnosis based on a change in detection sensitivity of a neutron detector, and update the neutron detector with respect to a periodic inspection period. An object of the present invention is to provide a lifetime diagnostic system for a neutron detector that is optimized and reduces costs.

In order to solve the above-mentioned problems, a neutron detector lifetime diagnosis system according to the present invention includes a neutron detector, a measuring means for measuring an average square voltage of the neutron detector, and the neutron detector from a measurement value of the measuring means. Neutron detector lifetime evaluation means for evaluating the lifetime of the neutron detector, periodic inspection plan means for storing periodic inspection plan data, and the neutron detector lifetime determined by the neutron detector lifetime evaluation means and periodic inspection plan inspection means In the neutron detector lifetime diagnosis system comprising neutron detector update planning means for determining the detector update periodic inspection time from the plan data , the neutron detector lifetime evaluation means includes the current mean square voltage of the neutron detector Detection sensitivity measuring means for calculating a ratio between the value of the mean square voltage when the neutron detector is loaded, and a current sensitivity based on the calculated detection sensitivity. A means for obtaining a neutron sensitivity change transition curve A with respect to the integrated neutron irradiation dose up to, a means for comparing the neutron sensitivity change transition curve A with the neutron sensitivity change transition curve B obtained by the DC current method, and obtaining the difference; And determining means for determining the lifetime of the neutron detector based on the ratio of the difference with respect to the neutron sensitivity change transition curve A.

  According to the neutron detector lifetime diagnosis system of the present invention, lifetime diagnosis based on a change in detection sensitivity can be performed appropriately and more accurately, and the update of the neutron detector can be optimized for the periodic inspection period to reduce costs. be able to.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram showing a lifetime diagnostic system for a neutron detector according to a first embodiment of the present invention, and FIG. 2 is a flowchart for explaining a lifetime diagnostic method.

  In FIG. 1, 1 is a neutron detector of a local output region monitor, 2 is a signal measuring device connected to the neutron detector 1 through a high voltage conductor 3, and this signal measuring device 2 is referred to as mean square voltage (hereinafter referred to as MSV). And a power supply (HV) 5 for applying a high voltage to the measurement circuit 4 and the neutron detector 1.

  Here, in order to reduce the quantity of the signal measuring device 2, the MSV measuring circuit 4 and the power source (HV) 5 are built in the same signal measuring device 2, but the MSV measuring circuit 4 and the power source (HV) 5 are used. And may be installed individually.

  Reference numeral 6 denotes a data collection device which is connected to the signal measuring device 2 and has a storage medium for transmitting a detection signal caused by the neutrons measured by the signal measuring device 2 and storing the measurement data.

  Here, when the measurement data from the signal measuring device 2 is stored in the data sampling device 6, the measurement date and time, the identification number of the neutron detector (loading position coordinates, serial number, etc.), etc. are stored at the same time. Identification is easy and is convenient when calculating the sensitivity of the neutron detector described later.

  Further, as a storage medium of the data collection device 6, a generally used one such as a hard disk or an MO disk can be used, and a display device such as an LCD or a CRT can be used.

  Reference numeral 7 denotes a neutron detector lifetime evaluation apparatus that evaluates the lifetime of the neutron detector 1 based on measurement data stored in the data sampling apparatus 6. Reference numeral 8 denotes a neutron detector lifetime evaluation apparatus 7 and a periodic inspection planning apparatus 9 of a power plant. Is a neutron detector renewal planning device to which the signal is input.

  Next, a method of calculating the detection sensitivity of the neutron detector from the measurement data of the MSV measurement circuit 4 in the neutron detector lifetime evaluation apparatus 7 will be described using the flowchart of FIG.

  First, the current MSV value of the neutron detector 1 is detected by the MSV measuring circuit 4 of the signal measuring device 2, and the neutron amount is measured based on this value to monitor the normal core power (S101). ).

Next, it is detected using the MSV signal data of the neutron detector 1 obtained in step (S101) and MSV ₀ (S102) which is an initial MSV value measured in advance at the initial stage of loading of the neutron detector. The ratio MSV / MSV ₀ between the current MSV value and the initial MSV ₀ value is calculated (S103), and the detection sensitivity is measured.

  Similarly, at the neutron detector position obtained by the core performance calculation, the integrated neutron irradiation amount from when the neutron detector is loaded inside the reactor until the detection sensitivity measurement is performed is calculated (S104). A neutron sensitivity change transition curve is plotted on a graph to obtain a neutron sensitivity change transition curve A as shown in FIG. 3 (S105).

Here, when the neutron sensitivity change transition curve A is plotted on the same graph as the neutron sensitivity change transition curve B of I / I ₀ obtained by the conventional DC current method, the DC current method is affected by gamma rays in addition to neutrons. As shown in FIG. 3, when both sensitivity change transition curves A and B are compared (S106), a difference D appears.

  As shown in FIG. 3, the neutron component and the gamma ray component have a relationship such that the ratio of the gamma ray component to the neutron component gradually increases as the amount of neutron irradiation increases. Thus, it is determined that the neutron irradiation time point P at which the gamma ray component is not negligible with respect to the neutron component is the lifetime of the neutron detector (S107).

  FIG. 4 is a flow chart showing the procedure of the neutron detector renewal planning device 8, with the neutron detector lifetime (S107) obtained by the MSV measurement method as the neutron detector lifetime diagnosis result (S111). 7, the remaining life time data of the neutron detector based on this neutron detector life diagnosis result (S111) is converted into days (S112), and this number of days from the start date of using the neutron detector Convert to day (S113).

  On the other hand, the periodic inspection plan data such as the lifetime of the neutron detector obtained by the neutron detector lifetime evaluation apparatus stored in the periodic inspection planning apparatus 9 of the power plant and the start date and the end date of the periodic inspection of the power plant (S114) Is input to the neutron detector renewal planning apparatus 8, and in this neutron detector renewal planning apparatus 8, the detector renewal power generation predetermined period inspection period is determined from the periodic inspection plan data (S114) and the neutron detector life date (S113). Is determined (S115), and update target neutron detector information for which the update time comes for each periodic inspection of the power plant is determined (S116).

  Here, if the neutron detector lifetime is further performed in units of time, a more accurate evaluation can be performed, and this evaluation can be used even when there is a neutron flux change that cannot be ignored.

Further, although the data collection device 6, the neutron detector lifetime evaluation device 7, and the neutron detector update planning device 8 shown in FIG. 1 are shown individually, they may be installed as the same device.
Further, this method can be automatically executed by software processing, and the switching cycle can be arbitrarily set.

  As described above, according to the neutron detector lifetime diagnosis system according to the first embodiment of the present invention, the average square voltage is detected and signal-processed in the lifetime diagnosis of the neutron detector. It is not affected by the accuracy of the calculation function of the process computer, and the lifetime of the neutron detector can be diagnosed with high accuracy by eliminating the influence of the gamma ray component.

  Further, the update execution time of the neutron detector is determined from the calculated remaining life of the neutron detector, and the detector update power generation predetermined period inspection time is determined from this and the periodic inspection plan data stored in the power generation predetermined period inspection plan apparatus. Since it is determined and the neutron detector information to be updated for each predetermined generation inspection is determined, the update time of the neutron detector can be optimized with respect to the periodic inspection period of the power plant.

  For this reason, it is not necessary to lengthen the periodic inspection period of the power plant more than necessary, and the cost can be reduced.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic configuration diagram of a lifetime diagnosis system for a neutron detector according to the second embodiment of the present invention.

  In the present embodiment, first, the lifetime of the neutron detector is calculated from the degree of decrease in the calibration current value calculated by the DC current method which is the conventional neutron detector lifetime diagnosis method shown in the flowchart of FIG. From the lifetime evaluation result (S121), the detector update power plant power generation predetermined period inspection period is determined by the DC measurement detector update plan (S122).

  This discrimination (S122) is based on the life evaluation result (S121) calculated from the neutron detector life evaluation diagnosis result (S111) by the DC current method in the evaluation flow of the neutron detector life evaluation apparatus 7 shown in FIGS. In the same manner, the periodic inspection time is determined.

On the other hand, the MSV measurement method is determined from the MSV measurement method life evaluation result (S123) of the evaluation flow of the neutron detector life evaluation device 7 shown in FIG. (A124) and quantitatively comparing this result with the above result (S122) (S125). As comparison items, there are a difference in life days, a life time difference, a difference in the number of periodic inspections, and a plurality of neutron detectors for each periodic inspection. Calculate renewal quantity difference.
This calculation result is displayed using an LCD, CRT, etc. (not shown).

  According to the present embodiment, it is possible to compare and display the economy by comparing the results of the conventional DC current method life evaluation and the MSV measurement method life evaluation, and quantitatively determine the update time of the neutron detector. Can be visualized, and the renewal time of the neutron detector can be further optimized.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a schematic configuration diagram of a lifetime diagnosis system for a neutron detector according to the third embodiment of the present invention.

  In the present embodiment, first, the neutron detector replacement work period (S131) is calculated from the neutron detector renewal planning device 8.

  Further, the fuel movement target is searched based on the detector position information (S132) stored in the neutron detector update planning device 8 (S133), and the fuel replacement plan (S134) registered in the fuel replacement work plan (S134). A fuel exchange period and a movement period are calculated from S135), and a work period related to fuel is calculated (S136).

  In addition, as representative examples of other work in the reactor, the control rod (CRD) work period (S138) based on the control rod (CRD) work plan (S137), the neutron detector replacement work period (S131) and the fuel are involved. A work process is generated from the work period (S136) (S139), and from this work process (S139) and the periodic inspection plan (S140) of the power plant, it is periodically determined whether the work process is within the periodic inspection period of the power plant. The determination is made by the in-period determination function (S141).

As a result, if there is no problem within the regular inspection period, the update plan is confirmed (S142), and if the regular inspection period is exceeded, the detector update plan is changed (S143).
The renewal plan is changed from a detector with a limited life to one periodical inspection.

  According to the present embodiment, the replacement work period of the neutron detector to be updated, the fuel exchange period, and the fuel transfer period are calculated to generate a work process, and whether this work process is within the periodic inspection period. Since the determination is made, the update time of the neutron detector can be further optimized.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic configuration diagram of a lifetime diagnosis system for a neutron detector according to the fourth embodiment of the present invention.

  In the present embodiment, first, the fuel movement target (S133), the fuel replacement target (S144), the fuel rotation (from the position information (S132) of the neutron detector to be updated stored in the neutron detector renewal planning device 8) A target (S145) for shuffling is searched, and the fuel moving order, moving distance, moving speed, and the like are calculated (S146) so as to minimize the fuel replacement time, and a fuel replacement plan is generated (S147).

  The embodiment shown in FIG. 7 generates an exchange plan that minimizes the total fuel exchange time for each periodic inspection unit for a plurality of neutron detectors.

  According to the present embodiment, the fuel moving order, moving distance, moving speed, etc. are calculated so that the fuel replacement time is minimized, and the fuel replacement plan is generated. The neutron detector can be updated.

  Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a schematic configuration diagram of a lifetime diagnosis system for a neutron detector according to the fifth embodiment of the present invention.

  In the present embodiment, first, the fuel movement target is searched from the position information (S132) of the neutron detector to be updated stored in the plurality of neutron detector renewal planning devices 8 (S133), and the fuel replacement target (S144). ), A fuel replacement work plan (S134) for calculating the fuel moving order, moving distance, and moving speed from the fuel replacement work planning function indicating the fuel rotation target (S145), and planning to minimize the fuel replacement time. And a control rod based on a control rod (CRD) work plan (S137) and a detector exchange work step (S148) for planning a detector replacement work step from position information (S132) of a plurality of neutron detectors to be updated (CRD) Function to generate a process plan to complete the work in the shortest time from the work period (S138) (S149), from the above work and target to the above process The work procedure manual generation function (S150) that creates a work procedure document that defines the work procedure as standard, and supplies necessary for neutron detector renewal, refueling, CRD work, etc. are set in advance. A product supply function (S151) capable of automatically procuring products from the implementation target is provided.

  According to the present embodiment, the work procedure manual generation function (S150) for creating a work procedure manual in which the work procedure is standardized in advance from the above-described implementation work and target in the process, and neutron detector updating and fuel exchange In addition, the supplies required for the CRD work etc. are set in advance and the supply function (S151) that can automatically procure the supplies from the implementation target in the process is provided, so the work is standardized, and the efficiency is reduced in a shorter time The renewal time of the neutron detector can be optimized.

  Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a schematic configuration diagram of a lifetime diagnosis system for a neutron detector according to a sixth embodiment of the present invention.

  The factors that determine the lifetime of a neutron detector include the nuclear lifetime where the detection sensitivity deteriorates when irradiated with thermal neutrons, and the service life of the structural materials that make up the neutron detector assembly. The life of the detector can be comprehensively determined by determining the life of the neutron detector as soon as it reaches the replacement standard among the life evaluated from the above viewpoint. FIG. 9 is a flowchart showing a method for carrying out these in the neutron detector lifetime evaluation apparatus 7.

  First, the flow (S101 to S106) for evaluating the nuclear lifetime of the neutron detector is as described in the first embodiment of the present invention. By this method, the nuclear lifetime of the neutron detector can be obtained (S161).

  On the other hand, in order to evaluate the service life of the structural material of the neutron detector assembly, the fast neutron irradiation amount (S162) obtained from the core performance calculation or the like is compared with a preset exchange reference value (S163). The time when the fast neutron irradiation amount reaches the exchange reference value is obtained as the service life of the structural material of the neutron detector assembly. Here, the fast neutron irradiation dose can be calculated by using the core performance calculation function used in the process computer of the plant, but the future cycle operation plan (core fuel arrangement, etc.) such as the next cycle or the cycle after the next If used, it is possible to predict the future dose with the same function. In addition, the exchange reference value set in advance is easier to compare if it is set as the neutron irradiation amount.

  In this way, by evaluating the lifetime from the viewpoints of both the nuclear lifetime where the detection sensitivity deteriorates due to thermal neutron irradiation and the service life of the structural materials that make up the neutron detector assembly, It is possible to make a practical life determination, and a more practical life determination.

  In the embodiment described above, the present invention can be carried out by adding the embodiment as follows.

(1) The neutron irradiation amount is calculated from the position information of the neutron detector so that the lifetime of the neutron detector is ensured until the renewal periodic inspection determined by the neutron detector renewal planning function. A function for generating and displaying the result is provided.

(2) A function is provided for generating a control rod position change operation plan that minimizes the number of fuel changes accompanying the neutron detector update.

(3) A function to generate a reactor control rod position change operation plan that minimizes the number of fuel movements and to correct the reactor control rod position change operation plan so that the fuel movement numbers coincide with each other during periodic inspections of neutron detector renewal Is provided.

(4) A means for determining the inspection cycle, inspection evaluation result, and handling state of the neutron detector, confirming and displaying the result, and providing a discrimination function for guaranteeing the life evaluation result according to the determination result.

(5) A function for automatically performing neutron sensitivity measurement, calculation, planning, and data generation and enabling the data update cycle to be arbitrarily set is provided.

(6) A reward calculation function is provided according to the difference in the number of days of renewal, the difference in the number of periodic inspections, the predicted number of plant usage period updates, the difference in weight of the waste detector, and the difference in the number of update detectors for each periodic inspection.

(7) Estimate the reduction amount of the fuel replacement quantity during the plant usage period, and provide a compensation calculation function according to the purchase cost, waste disposal cost and taxation incurred when the reduced fuel is used.

(8) Applicable to neutron detectors used in reprocessing facilities, waste disposal facilities, fuel storage facilities, research facilities, medical facilities, and mine facilities.

The system block diagram which shows the lifetime diagnostic system of the neutron detector by the 1st Embodiment of this invention. The flowchart which shows the lifetime diagnostic method of the neutron detector by the 1st Embodiment of this invention. The characteristic view which shows the relationship between the sensitivity ratio of the neutron detector and neutron irradiation amount in the 1st Embodiment of this invention. The flowchart which shows the procedure of the neutron detector update plan apparatus in the 1st Embodiment of this invention. The schematic block diagram which shows the lifetime diagnostic system of the neutron detector by the 2nd Embodiment of this invention. The schematic block diagram which shows the lifetime diagnostic system of the neutron detector by the 3rd Embodiment of this invention. The schematic block diagram which shows the lifetime diagnostic system of the neutron detector by the 4th Embodiment of this invention. The schematic block diagram which shows the lifetime diagnostic system of the neutron detector by the 5th Embodiment of this invention. The schematic block diagram which shows the lifetime diagnostic system of the neutron detector by the 6th Embodiment of this invention. The characteristic view which shows the relationship between the sensitivity ratio of the conventional general neutron detector and neutron irradiation amount. The flowchart which shows the procedure of the lifetime diagnostic system of the conventional neutron detector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Neutron detector, 2 ... Signal measuring device, 3 ... High voltage conductor, 4 ... Mean square voltage measuring circuit, 5 ... Power supply (HV), 6 ... Data sampling device, 7 ... Neutron detector lifetime evaluation device, 8 ... Neutron Detector update planning device, 9 ... periodic inspection planning device.

Claims (6)

Stores neutron detector, measuring means for measuring the mean square voltage of the neutron detector, neutron detector life evaluating means for evaluating the life of the neutron detector from the measured value of the measuring means, and periodic inspection plan data Neutron detector renewal plan means for discriminating a detector renewal periodic inspection time from the neutron detector life determined by the neutron detector life evaluation means and the periodic inspection plan data of the periodic inspection plan means In a neutron detector lifetime diagnosis system comprising:
The neutron detector lifetime evaluation means includes a detection sensitivity measurement means for calculating a ratio between a current mean square voltage value of the neutron detector and a mean square voltage value when the neutron detector is loaded, and the calculated The means for obtaining the neutron sensitivity change transition curve A with respect to the integrated neutron irradiation dose based on the detection sensitivity is compared with the neutron sensitivity change transition curve A and the neutron sensitivity change transition curve B obtained by the DC current method. A neutron detector lifetime diagnostic system comprising: means for obtaining a difference; and determination means for determining a lifetime of the neutron detector based on a ratio of the difference to the neutron sensitivity change transition curve A. The lifetime of the neutron detector calculated from the measurement value of the measuring means and the lifetime of the neutron detector calculated from the change in the calibration current value of the neutron detector are compared. lifting system of the neutron detector according to claim 1, wherein the comparing display calculates a plurality of neutron detectors updating quantity difference periodic inspection differential number and each periodic inspection.   Based on the position information of the neutron detector to be updated, a work process is generated by calculating a replacement work period, a fuel exchange period, and a fuel transfer period of the neutron detector to be updated. 2. The lifetime diagnostic system for a neutron detector according to claim 1, wherein the system has a function of discriminating whether or not the work process is within a periodic inspection period of a power plant from a periodic inspection plan. Search the fuel movement target, fuel replacement target, fuel rotation target from the position information of the neutron detector to be updated, calculate the fuel movement order, movement distance, movement speed so that the fuel movement time is the shortest, 4. The neutron detector lifetime diagnosis system according to claim 3, further comprising a neutron detector renewal work plan function for generating a fuel exchange plan. Based on position information of the plurality of neutron detectors to be updated, a detector replacement process planning function for planning a detector replacement process, and a reactor control rod for planning a reactor control rod inspection or replacement process The neutron detector lifetime diagnosis system according to any one of claims 1 to 4, further comprising a process plan, a work procedure generation, and a product supply function so as to complete the work in the shortest time from the work plan function.   The lifetime of the neutron detector is determined from the nuclear life obtained from the measured value of the square voltage of the neutron detector and the service life of the structural material of the neutron detector assembly, whichever comes first. The neutron detector lifetime diagnosis system according to claim 1, further comprising a neutron detector lifetime evaluation unit for performing the neutron detector lifetime evaluation.

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