JP2008175692A - Measuring method of axial power distribution of core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure the axial power distribution of the core in various core states. <P>SOLUTION: In this measuring method, the axial power distribution of the core during operation is measured based on a measured value of a neutron detector mounted in a plurality of places along the axial direction of a pressure vessel and an expression showing the relation between the axial power distribution of the core and the measured value of the neutron detector. This measuring method comprises an analysis expression creation step of creating an analysis expression showing the relation between the axial power distribution of the core and the measured value of the neutron detector regarding, as a target, the core state whose axial power distribution of the core is actually measured, an analysis expression correction step of correcting the analysis expression created in the analysis expression creation step diverting data for correcting the analysis expression obtained using the actual operation of the nuclear reactor in another core state, and a core axial power distribution measurement step of using the measured value of the neutron detector and the expression obtained by correcting the analysis expression in the analysis expression correction step during operation of the nuclear reactor in the core state as the target of the analysis expression creation step. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for measuring the axial power distribution of a core (hereinafter, also simply referred to as “axial power distribution”), and in particular, an analytical expression derived for a core state to be measured from now on is actually used for other core states. Make the necessary corrections based on the data about the difference between the analytical formulas already obtained in operation and the measured values, and use the analytical formulas after the corrections to measure the axial power distribution. The present invention relates to a distribution measurement method.

  In boiling water reactors as well as pressurized water reactors, neutron leakage occurs in the vertical direction (hereinafter also referred to as “axial” or “axial”), and the temperature distribution in the reactor is also different. Therefore, the neutron distribution in the axial direction of the core differs from the axial power distribution (axial offset. Hereinafter, in principle, it is described as “A.O.” except for the claims). Therefore, in order to perform safer and more efficient operation of the reactor, A. O. Must be measured accurately.

For this reason, the following measurement methods have been generally employed, particularly in pressurized water reactors.
First, a sensor called a movable microneutron detector is inserted into the instrument assembly thimble tube at a plurality of locations along the axial direction of the outer wall of the reactor pressure vessel (the positions in the axial direction are different). In addition, a neutron detector is installed, and the control rod is further operated to moderately vibrate the power distribution in the axial direction of the reactor. In this state, the movable micro neutron detector is scanned in the axial direction to actually perform A . O. At the same time, neutrons are also measured by each neutron detector (hereinafter, “each” is omitted) mounted on the outer wall of the pressure vessel.

Next, the measured value of the movable microneutron detector is correct. O. Each A. is measured. O. In this state, the neutron detectors mounted at a plurality of locations along the axial direction of the outer wall of the pressure vessel output what values are output as neutron measurement values. That is, each A.E. O. Data (calibration data) representing the relationship between the state of and the actual output of the corresponding neutron detector.
At the time of steady operation of the reactor, based on the measured values of neutrons output from the neutron detectors mounted at a plurality of axial positions on the outer wall of the pressure vessel and the calibration data, A. O. Estimate Therefore, an indirect measurement method is adopted.

  However, this method is performed with the reactor power reduced by about 25% from the viewpoint of ensuring safety, and xenon vibration that does not occur during normal operation (core generated with the axial movement of the control rod). As a result of the difference between the overall power fluctuation and the power distribution in the axial direction of the core, the concentration of xenon that absorbs neutrons changes with time in the whole core and the axial direction of the core, and the resulting core and core axes are generated accordingly. It is not desirable from the viewpoint of the economics of the operation of the nuclear reactor that the equipment cost is extremely high.

Therefore, as conceptually shown in FIG. 2, an invention for measuring by adopting an analytical technique has been made and put into practical use (Patent Document 1). The technical contents will be described below with reference to FIG.
First, the inside of the reactor is virtually divided into several locations in the axial direction, and the neutron density at each of the divided locations and the neutron detectors installed at multiple locations along the axial direction of the outer wall of the pressure vessel Analyze how the measured values relate to each other.

This state is shown in (1) and (2) of FIG.
In FIG. 2 (1), 10 is the core of a pressurized water reactor, and 20 is the pressure vessel wall of the reactor near the core 10. On the outer periphery of the reactor pressure vessel wall 20 near the core 10, neutron detectors 21, 22, 23, 24, 25 are mounted, for example, at five locations in order from the top.

In order to analytically derive the expression representing the relationship between the axial power distribution of the core 10 and the measured values of the neutron detectors 21, 22, 23, 24, 25, as shown in (1) of FIG. The core is virtually divided into five regions indicated by 11, 12, 13, 14, and 15 in order from the top (the actual core has an integral structure).
Further, J1, J2, J3, J4, and J5 are the output states of the respective regions of the core 10 that are divided into five in order from the top, and C1, C2, C3, C4, and C5 are respectively in order from the top. The measured values of the neutron detectors 21, 22, 23, 24, and 25 attached to the reactor pressure vessel 20.

  In FIG. 2 (1), for the convenience of explanation, the number of virtual divisions in the vertical direction of the core and the number of neutron detectors mounted in the vertical direction on the outer peripheral wall of the nearby reactor pressure vessel are as follows. Although both are set to 5, these are not limited to 5 and may be different from each other. In the case of an actual nuclear reactor, there are generally eight in two axial directions, four at the same height in the upper part and four at the same height in the lower part.

  Based on the above, several cases are assumed in which the power distribution in the axial direction in the reactor, and thus the neutron distribution, is different using the two-dimensional transport code or the like in the same core state. Next, in each case, how are the measured values C1, C2, C3, C4, C5 of the neutron detectors 21, 22, 23, 24, 25 mounted at a plurality of locations along the axial direction of the outer wall of the pressure vessel? Or the measurement value to be output, the distance between the neutron detector and the neutron source, the angle that the neutron detector occupies with respect to the neutron source, the absorption of neutrons by boron in cooling water, etc. In consideration, each case is obtained by analysis.

The obtained results are shown in the following formula (1).
Rc = A × A. O. + B (1)
Here, Rc is a distribution of intensity of neutron flux (flow of neutrons escaping outside the reactor) measured (output) by neutron detectors mounted at a plurality of locations along the axial direction of the outer wall of the pressure vessel. That is, C1, C2, C3, C4, and C5 are out-of-core detector responses expressed by a one-dimensional vector arranged in a line in the vertical direction.
A. O. Is the power distribution J1, J2, J3, J4, J5 of each region in the axial direction of the virtually divided core, that is, the distribution of neutrons in the axial direction of the core, which is also expressed by a one-dimensional vector in the longitudinal direction. Is done.
(2) of FIG. O. The contents of the determinant consisting of B and B are shown visually.

Since calculations were performed assuming a plurality of cases in which the axial neutron distribution in the furnace is different, J1, J2, J3, J4, and J5 shown in FIG. 2 (1) are eventually C1, C2, and C3. A and B shown in (2) of FIG. 2 are obtained by calculating a plurality of states in which C4 and C5 are different from each other, averaging the calculated values, and using the least square method.
For this reason, B may be zero.

  Note that the neutron flux measurement by the neutron detector is not only actually output as a current value, but also has different sensitivities depending on the neutron flux spectrum (neutron energy distribution) and the like. Furthermore, there are certain limits that arise from the analysis itself, such as the two-dimensional transport theory and the assumption of neutron flux decay, and the accuracy of the constants used in the analysis. For these reasons, it is necessary to correct an equation created by analysis using actual operation, that is, to compensate for a deviation generated between the neutron flux and the measured current value. Therefore, finally, the operation of one cycle is completed in the actual nuclear reactor, and when Rc and A.I. O. And make necessary corrections for A and B.

  Note that one correction coefficient is required for each of A and B to correct equation (1) and obtain equation (2) shown later, but only A may be corrected depending on conditions. In this case, if the correction count is K and the measurement current is I, K = I / (Rc).

The corrected formula is shown in (3) of FIG.
The corrected equation (1) is expressed as Rc = A ′ × A. O. It can be expressed as + B ′. This is defined as equation (2).
Here, A ′ is a matrix composed of a′11,..., A′55 after correcting a11,..., A55, and B ′ is after correcting b1,. Is a one-dimensional vector in the vertical direction composed of b′1,..., B′5.

  Under the above, Rc is measured during the operation of the nuclear reactor, and A. O. Will be measured indirectly.

In Patent Document 1, “AO” is used instead of “A.O.”, and AO is defined as follows.
AO = (Pr−Ps) / (Pr + Ps)
Here, Pr is the output of the upper half of the reactor, and Ps is the output of the lower half. In other words, the axial power distribution is measured by dividing the core into two parts. This is not essentially different from the description that the core is divided into five parts in the axial direction and the output of each divided part is different.

Japanese Patent Publication No. 4-33000

  By the way, in the above invention, A. O. In this measurement, an analytical expression is created assuming several cases with different axial power distributions, and correction is made in actual operation, but basically it is based on one specific core state. In addition, for example, an equation (calibration equation or calibration data) obtained by calibrating an analytical equation created based on one operation state in which 100% output is maintained is used.

  However, in an actual nuclear reactor, various states of the core are variously changed and complicated. For this reason, various parameters such as furnace power, burnup, and boron concentration change more complicatedly than before. For example, if the boron concentration in the cooling water is different, the absorption coefficient of neutrons used in the analysis is different. As a result, various constants used in the analytical expression are also different.

In addition, the position of the control rod that absorbs neutrons in the furnace can be changed depending on the operating state and the furnace power, and the temperature of the cooling fluid in the upper part of the furnace, such as light water, is also different. The neutron detectors mounted at a plurality of locations along the axial direction of the outer wall of the reactor pressure vessel may have complex and different response characteristics at the upper and lower portions of the core.
As a result, the intensity of the neutron flux output from the core power and the neutron detector as a current value is not a simple proportional relationship. For example, when the reactor power is changed from 50% to 100%, the current value as a whole is accurately 2 It doesn't double. That is, it changes complicatedly in the state of the core.
For this reason, the relationship between the axial power distribution of the core and the measured values of the neutron detectors installed at a plurality of locations along the axial direction also changes in a complicated manner.

That is, since the calibration formula in the above invention is created based on one specific core state, there is a certain limit in accuracy in a core state that is significantly different from that.
For this reason, in a core state that is significantly different from the core state that has been calibrated, it has been necessary to perform calibration inside and outside the reactor during steady operation.
Furthermore, the A.A. O. Development of technology that can measure

  The present invention has been made for the purpose of solving the above problems, and in order to measure the axial power distribution of the core in a new core state, an analytical expression newly derived for the core state, Make necessary corrections using the data to correct the analytical formula obtained using actual measurements during operation in other core conditions, and measure the axial power distribution using the revised analytical formula. This is what I did. The invention of each claim will be described below.

The invention described in claim 1
Based on the measured values of the neutron detectors installed at multiple locations along the axial direction of the pressure vessel and the formula representing the relationship between the axial power distribution of the core and the measured values of the neutron detector A method for measuring the axial power distribution of the core of
Analytical expression creating step for creating an analytical expression representing the relationship between the axial power distribution of the core and the measured value of the neutron detector for the core state that will actually measure the axial power distribution of the core; ,
An analytical formula correction step for correcting the analytical formula created in the analytical formula creation step by using data for correcting the analytical formula obtained by utilizing the actual operation of the reactor in another core state, ,
During the operation of the reactor in the core state targeted by the analytical formula creation step, the measured value by the neutron detector and the formula obtained by correcting the analytical formula in the analytical formula correction step are used. A measuring step of measuring the axial power distribution of the core.

  In the invention of this claim, the measurement of the axial power distribution of the core performed during the operation of the nuclear reactor is performed by measuring actual measured values of neutron detectors installed at a plurality of locations along the axial direction of the pressure vessel. This is done indirectly based on the equation representing the relationship between the axial power distribution of the core and the measured value of the neutron detector. At this time, an analysis created for the core state that is currently being measured Make necessary corrections to the formula to correct the analytical formula obtained by using actual measurements during operation in other core conditions, and use the corrected analytical formula to perform the axial direction. Since the power distribution is measured, the measurement accuracy of the axial power distribution of the core in various core states is improved.

  Further, since the measurement accuracy is improved, it is possible to eliminate the need for calibration inside and outside the furnace during steady operation, which has been conventionally performed, and to reduce the number of calibrations.

Here, the “core state” means the average output and maximum output of the core that is continuously operated, whether there is output fluctuation during continuous operation, the type of fuel in the reactor, maximum burnup, current burnup, The state of the core and the state of operation using parameters such as the type and arrangement of each fuel (aggregate), the boron concentration in the cooling water, the position of the control rod, and the like.
The “operation in another core state” may be another nuclear reactor as long as data for correcting the analytical expression can be used.

  In addition, the analytical formulas for each core state are created by appropriately assuming the axial power distribution of the core within the range that seems to be appropriate under the target core state. If the idea is the same, the details may be different. For example, the number of virtual divisions in the axial direction of the core may be the same or different. In addition, the number of cases of the axial power distribution of the core that is appropriately assumed may be the same or different.

Further, the assumed axial power distribution of the core may be assumed based on empirical rules.
The “analytic expression” includes not only pure theory and calculation but also an expression created by reflecting already obtained empirical rules, actual measurement data, and the like.
In addition, “data that corrects the analytical formula obtained by using the actual operation of the reactor in other core states” means the actual neutron flux in the neutron measuring instrument and the current value output as the measured value. In addition, data for compensating for an error occurring in is based on actual measurement.
In addition, a book that measures the axial power distribution using a formula that has been corrected by using the data that corrects the analytical formula obtained by utilizing the actual operation of the reactor in other core conditions. Under the spirit of the invention, the difference between the actual measurement and the analytical expression in a plurality of core states has been studied, and therefore there are a plurality of data for correcting the analytical expression, and measurement will be performed using these multiple data. The analytical expression for the core state may be modified.

The invention according to claim 2 is a method of measuring the axial power distribution of the core,
The analytical formula correcting step includes:
Analytical formula creation procedure for obtaining analytical formulas representing the relationship between the axial power distribution of the core and the measured values of the neutron detectors installed at multiple locations along the axial direction of the pressure vessel for other core conditions When,
Using the operation of the reactor in the other core state, the relationship between the axial power distribution of the core in the core state and the measured value of the neutron detector is actually measured and created by the analytical formula creation procedure. A data acquisition procedure for correction to acquire data for correction so that the analytical expression represents a correct relationship;
The axial power distribution of the reactor core has a correction procedure for correcting the analytical formula created in the analytical formula creation step by diverting the data obtained in the correction data acquisition procedure This is a measurement method.

  In the invention of this claim, the correction of the analytical expression created for the core state that will actually measure the axial power distribution of the core is the axial power distribution of the core for other core states. And an analytical expression representing the relationship between the measured values of the neutron detectors installed at multiple locations along the axial direction of the pressure vessel, and further using the operation of the reactor in the core state, Actually measure the relationship between the axial power distribution of the reactor core and the measured value of the neutron detector, acquire data to correct the analytical formula to represent the correct relationship, and use that data. The correction is appropriate because it is made by correcting an expression created by analysis for the core state as a new measurement target.

The invention described in claim 3
Based on the measured values of the neutron detectors installed at multiple locations along the axial direction of the pressure vessel and the formula representing the relationship between the axial power distribution of the core and the measured values of the neutron detector A method for measuring the axial power distribution of the core of
The axial direction of the core in the first core state in which a formula corrected to be actually adapted based on the measurement during the operation of the nuclear reactor has already been obtained and in the second core state in which the actual measurement will be performed from now on An examination step for examining a difference occurring in an analytical expression representing a relationship between an output distribution and a measurement value of the neutron detector,
Based on the result of the examination in the examination step, the equation corrected so as to be actually adapted to the first core state, the axial power distribution of the core intended for the second core state, and the neutron detector A correction step that corrects the relationship to the measured value of
During the operation of the reactor in the second core state, there is a measurement step for measuring the power distribution of the core in the axial direction using the measurement value by the neutron detector and the formula corrected in the correction step. It is the measuring method of the axial direction power distribution of the core characterized by the above-mentioned.

  The invention according to the present invention relates to an A.D. O. Based on the equation used for the measurement of the core, but the core state is different but has been corrected by actual measurement in actual operation, the difference that occurs in the analytical equation due to the difference in the core state is examined, and Since the correction is made, the measurement accuracy of the axial power distribution of the core in the new core state is improved.

  Further, since the measurement accuracy is improved, it is possible to eliminate the need for calibration inside and outside the furnace during steady operation, which has been conventionally performed, and to reduce the number of calibrations.

The invention according to claim 4
Based on the measured values of the neutron detectors installed at multiple locations along the axial direction of the pressure vessel and the formula representing the relationship between the axial power distribution of the core and the measured values of the neutron detector A method for measuring the axial power distribution of the core of
An analytical expression creating step for obtaining an analytical expression representing the relationship between the axial power distribution of the core in the first core state and the measured value of the neutron detector;
Using the operation of the reactor in the first core state, the relationship between the axial power distribution of the core in the first core state and the measured value of the neutron detector is actually measured, and the analytical expression is correct Analytical formula correction step for correcting the relationship to be expressed,
Examining the difference between the second core state, which is the core state to be actually measured, and the first core state, further modifying the analytical formula corrected in the analytical formula correcting step based on the examination results, A formula creating step for obtaining a formula that correctly represents the relationship between the axial power distribution of the core in the core state of 2 and the measured value of the neutron detector;
During the operation of the reactor in the second core state, the measured value actually measured by the neutron detector and the formula obtained in the formula creation step are used to calculate the core in the second core state. It is a measuring method of the axial power distribution of a core characterized by having a measurement step which measures axial power distribution.

  The invention of this claim provides an analytical expression representing the relationship between the axial power distribution of the core in the first core state and the measured values of the neutron detectors installed at a plurality of locations along the axial direction of the pressure vessel. , Corrected to reflect the actual measurement results of the axial power distribution of the core and the measured values of the neutron detector using the operation of the reactor in the core state, and in the core state to be actually measured in the revised formula Analyzing the difference between the second core state and the first core state, making further corrections, and expressing the relationship between the axial power distribution of the core and the measured value of the neutron detector in the second core state Therefore, the measurement accuracy of the axial power distribution of the core in the new core state is improved.

  In addition, the measurement accuracy is improved, and it is possible to eliminate the need for calibration inside and outside the furnace during steady operation, which has been conventionally performed, or to reduce the number of calibrations.

The invention according to claim 5 is a method of measuring the axial power distribution of the core,
The neutron detectors installed at a plurality of locations along the axial direction of the pressure vessel are at least partially equipped on the outer wall or outside of the pressure vessel, and the axial power distribution of the reactor is characterized in that This is a measurement method.

  In the invention of this claim, the neutron detectors installed at several locations in the axial direction are provided at least partially on the outer wall or outside of the reactor pressure vessel. Detectors can be mounted and adjusted, flexibility in measurement during operation can be increased, accuracy can be improved, and the core can be monitored constantly.

In the present invention, necessary correction is performed using the data for correcting the analytical expression obtained in the actual measurement in spite of other core states, and a new core state is determined using the corrected analytical expression. Since the axial power distribution is measured, the measurement accuracy of the axial power distribution of the core in various core states is improved.
For this reason, calibration inside and outside the furnace during steady operation, which has been conventionally performed, becomes unnecessary, and the number of calibrations can be reduced.

  Hereinafter, the present invention will be described based on the best mode. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

(First embodiment)
In the present embodiment, necessary corrections are made by diverting data for correcting analytical formulas obtained by actual measurements in other core states to formulas created by analysis for a certain core state. About.

FIG. 1 conceptually shows the procedure of the embodiment of the present invention. The procedure shown in (1) to (3) of FIG. 1 is the same as the procedure shown in (1) to (3) of FIG.
As shown in (1) of FIG. 1, assuming a standard core state (hereinafter, this core state is referred to as “core state 1”), a plurality of cases of A.D. O. Is assumed.

As shown in (2) of FIG. O. As described in the background art section, the out-of-core detector response (hereinafter, Rc in the core state 1 is referred to as “Rc1”) and A. O. Create an expression that shows the relationship.
That is, Rc1 = A1 × A. O. + B1 is obtained. Here, A1 and B1 are the same as A and B shown in (2) of FIG. 1, respectively, but are described in this way for convenience of later explanation.

As shown in (3) of FIG. 1, one cycle of operation is completed in an actual nuclear reactor, and when Rc1 and A.I. are actually started for the first time in the next cycle after fuel replacement. O. Is measured, and necessary corrections are made to the obtained A1 and B1.
As a result, the out-of-core detector response in the core state 1 (hereinafter referred to as “Rc1”) and the A.D. O. Rc1 = A1 ′ × A. O. + B1 ′ is obtained. Here, A1 ′ and B1 ′ are the same as A ′ and B ′ shown in FIG. 1 (3) respectively, but are also described in this way for convenience of later explanation.
Therefore, the steps so far are the same as those in the background art section described with reference to (1) to (3) in FIG.

  As shown in (4) of FIG. 1, correction data AS and BS are obtained. Here, AS = A1 '/ A1 and BS = B1' / B1.

As shown in FIG. 1 (5), as in (1) of FIG. O. Is assumed to be an actual core state (hereinafter referred to as “core state 2”).
As shown in (6) of FIG. 1, a plurality of A.D. O. A plurality of A.S. O. On the basis of the state of the reactor (hereinafter, Rc in the core state 2 is referred to as “Rc2”) and A. O. Is calculated.

  That is, Rc2 = A2 × A. O. + B2 is obtained. Here, A2 and B2 are obtained by the same method as A1 and B1 shown in FIG. 1 (2), but the operating state 1 and operating state 2 have different core states. O. Are often different values.

As shown in (7) of FIG. 1, the following correction is performed on A2 and B2 using the correction data AS and BS described in (4) of FIG. A2 and B2 after correction are denoted as A2 ′ and B2 ′, respectively.
A2 ′ = A2 × AS = A2 × (A1 ′ / A1)
B2 ′ = B2 × BS = B2 × (B1 ′ / B1)

As shown in FIG. 1 (8), in the reactor core state 2, the out-of-core detector response Rc2 and the A.D. O. This relationship can be expressed by the following equation.
Rc2 = A2 ′ × A. O. + B2 '

In addition, although the power distribution in the reactor is regarded as the intensity of the neutron flux, the neutron detector actually outputs the intensity of the neutron as the intensity of the current value. Core state 2 A.E. O. Measurement (indirect measurement by estimation) will be performed.
Further, in the present embodiment, the preferred form and technical contents of the present invention are generally described without being restricted by the type of the reactor, but in a pressurized water reactor for domestic power generation, The power distribution in the lower half axial direction is measured and monitored. For this reason, when neutron detectors are arranged at a number of locations in the axial direction as in the present embodiment, A.A. O. However, since the electric circuit for that purpose is easy, the description is omitted.

(Second Embodiment)
In the present embodiment, when an analytical formula that has been corrected based on actual measurement has already been obtained, it is necessary to reflect the difference in the core state in order to use it in the measurement of other core states. On making various corrections.

  Suppose a reactor has been operating continuously at 100% load for the first few months. This state is referred to as core state 1. At this time, the axial power distribution of the core is measured using the analytical formula created on the assumption that it is continuously operated at 100% load, using the time when the reactor is started. Based on the measured axial core distribution and the measured values of the neutron measuring instruments installed at multiple locations along the axial direction, the formula with the necessary corrections is used.

It is assumed that this nuclear reactor is continuously operated at a load of 70% for some reason such as the start of operation of another nuclear reactor or a reduction in power demand. This state is referred to as core state 2.
In this case, the neutron source, that is, the neutron density in each part of the core is reduced, and the boron concentration in the coolant is increased, resulting in a change in the internal state of the reactor, such as an increase in neutron absorption along the way. Although the measurement value of the measuring instrument becomes small, how much it becomes small can be easily obtained by examination centering on analysis. Therefore, the equation used for the core state 1 that is continuously operated at the 100% load is corrected to reflect the examination result, and the core state in which the operation is continuously performed at the 70% load. 2 will be used to measure the axial output distribution.

That is, if the correction factor for core state 1 is K and the correction factor for core state 2 (improved correction factor) is K ′, then K ′ = K × C. Here, C = a value indicating the difference between the core state 1 and the core state 2.
Alternatively, K ′ = {measured I of core state 1 / (measured Rc of core state 1)} {I of core state 2 calculated by analysis / I of core state 1 calculated by analysis} / {Rc of core state 2 calculated by analysis / Rc of core state 1 calculated by analysis}.

In-furnace detector response and A. O. It is a figure which shows notionally the procedure which calculates | requires the formula which shows these relationships. A prior art out-of-core detector response and A.I. O. It is a figure which shows notionally the procedure which calculates | requires the formula which shows these relationships.

Explanation of symbols

10 Core 11, 12, 13, 14, 15 Each region of the core virtually divided in the axial direction 20 Reactor pressure vessel walls 21, 22, 23, 24, 25 Neutron detector

Claims (5)

Based on the measured values of the neutron detectors installed at multiple locations along the axial direction of the pressure vessel and the formula representing the relationship between the axial power distribution of the core and the measured values of the neutron detector A method for measuring the axial power distribution of the core of
Analytical expression creating step for creating an analytical expression representing the relationship between the axial power distribution of the core and the measured value of the neutron detector for the core state that will actually measure the axial power distribution of the core; ,
An analytical formula correction step for correcting the analytical formula created in the analytical formula creation step by using data for correcting the analytical formula obtained by utilizing the actual operation of the reactor in another core state, ,
During the operation of the reactor in the core state targeted by the analytical formula creation step, the measured value by the neutron detector and the formula obtained by correcting the analytical formula in the analytical formula correction step are used. A measuring method for measuring the axial power distribution of the core, comprising the step of measuring the axial power distribution of the core. The analytical formula correcting step includes:
Analytical formula creation procedure for obtaining analytical formulas representing the relationship between the axial power distribution of the core and the measured values of the neutron detectors installed at multiple locations along the axial direction of the pressure vessel for other core conditions When,
Using the operation of the reactor in the other core state, the relationship between the axial power distribution of the core in the core state and the measured value of the neutron detector is actually measured and created by the analytical formula creation procedure. A data acquisition procedure for correction to acquire data for correction so that the analytical expression represents a correct relationship;
2. The method according to claim 1, further comprising a correction procedure for correcting the analytical formula created in the analytical formula creation step by diverting the data obtained in the correction data acquisition procedure. A method for measuring the axial power distribution of the core. Based on the measured values of the neutron detectors installed at multiple locations along the axial direction of the pressure vessel and the formula representing the relationship between the axial power distribution of the core and the measured values of the neutron detector A method for measuring the axial power distribution of the core of
The axial direction of the core in the first core state in which a formula corrected to be actually adapted based on the measurement during the operation of the nuclear reactor has already been obtained and in the second core state in which the actual measurement will be performed from now on An examination step for examining a difference occurring in an analytical expression representing a relationship between an output distribution and a measurement value of the neutron detector,
Based on the result of the examination in the examination step, the equation corrected so as to be actually adapted to the first core state, the axial power distribution of the core intended for the second core state, and the neutron detector A correction step that corrects the relationship to the measured value of
During the operation of the reactor in the second core state, there is a measurement step for measuring the power distribution of the core in the axial direction using the measurement value by the neutron detector and the formula corrected in the correction step. A method of measuring the axial power distribution of the core, characterized in that Based on the measured values of the neutron detectors installed at multiple locations along the axial direction of the pressure vessel and the formula representing the relationship between the axial power distribution of the core and the measured values of the neutron detector A method for measuring the axial power distribution of the core of
An analytical expression creating step for obtaining an analytical expression representing the relationship between the axial power distribution of the core in the first core state and the measured value of the neutron detector;
Using the operation of the reactor in the first core state, the relationship between the axial power distribution of the core in the first core state and the measured value of the neutron detector is actually measured, and the analytical expression is correct Analytical formula correction step for correcting the relationship to be expressed,
Examining the difference between the second core state, which is the core state to be actually measured, and the first core state, further modifying the analytical formula corrected in the analytical formula correcting step based on the examination results, A formula creating step for obtaining a formula that correctly represents the relationship between the axial power distribution of the core in the core state of 2 and the measured value of the neutron detector;
During the operation of the reactor in the second core state, the measured value actually measured by the neutron detector and the formula obtained in the formula creation step are used to calculate the core in the second core state. A measuring method of an axial power distribution of a core, comprising a measuring step of measuring an axial power distribution.   5. The neutron detectors installed at a plurality of locations along the axial direction of the pressure vessel are at least partially provided on the outer wall or outside of the pressure vessel. A method for measuring the axial power distribution of the core according to any one of the above.

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