Stepwise static reactor control rod worth measurement method

Abstract

The application discloses a kind of step-by-step static reactor control rod value measurement methods, comprising the following steps: make reactor and measured control rod initial state;Measured control rod is inserted to initial target rod position, and obtains initial reactivity difference in the process that measured control rod is inserted from initial state to initial target rod position;Make core supercritical state;Measured control rod is inserted to segmented target rod position, and obtains segmented reactivity difference in the process that measured control rod is inserted from supercritical state to segmented target rod position;The first two steps are repeatedly executed until measured control rod reaches reactor bottom;Each segmented reactivity difference is accumulated, and obtains cumulative result;Cumulative result and initial reactivity difference are summed, and the reactivity value of measured control rod is obtained.The method improves measurement accuracy, reduces measurement error, effectively solves the problem that the value measurement test result of the control rod with smaller value frequently exceeds the tolerance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nuclear power, in particular to a kind of step-by-step static reactor control rod value measurement method. BACKGROUND

[0002] Reactivity is a physical quantity reflecting the state of nuclear reactor, which represents the degree of reactor deviating from critical state, i.e., the relative deviation of effective multiplication factor K from critical value 1. The reactivity measurement of nuclear power plant is based on point reactor model, which receives the measurement current signal from the output of ex-core detector by using reactivity instrument, and obtains the reactivity of reactor by inverse dynamic calculation of point reactor neutron kinetics equation. Under given conditions, the absolute value of reactivity change caused by inserting a control rod completely withdrawn from the core into the core is the control rod value.

[0003] The principle of traditional boron adjustment method for measuring control rod value is as follows: when the reactor is in zero power physical test range, continuously and uniformly dilute or boronize the boron concentration of the reactor, and compensate the reactivity change caused by the change of boron concentration by continuously inserting or withdrawing the measured control rod to ensure that the reactor is near critical state; during the operation, the reactivity instrument reflects the reactivity change during the entire operation on the recording paper, and the technical personnel obtains the reactivity change intercept value during each rod movement by manually drawing a line on the reactivity change curve on the recording paper, converts the reactivity change corresponding to each rod position change by using the corresponding relationship between the recording paper grid and the reactivity channel range, and finally adds up all the reactivity changes corresponding to the complete insertion or complete withdrawal of the measured rod into the reactor to obtain the value of the entire control rod. The measured control rod value is compared with the theoretical rod value for acceptance, if the deviation between them is within the acceptance criteria, the measurement result is not out of tolerance, and the measurement test result is qualified.

[0004] In view of the problem that the traditional boron adjustment method has large measurement error and frequent unqualified measurement test results when measuring the value of small control rod, the boron adjustment measurement method is optimized, and a step-by-step static reactor control rod value measurement method is developed to improve the measurement accuracy, reduce the measurement error, effectively solve the problem of frequent out-of-tolerance of measurement test results of small control rod value in nuclear power field, and has very important practical significance and great popularization value for nuclear power plant. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a step-by-step static reactor control rod value measurement method.

[0006] The technical solution adopted by the present application to solve the technical problem is: a step-by-step static reactor control rod value measurement method is constructed, which comprises the following steps:

[0007] S1, adjusting the reactor and the measured control rod to initial states respectively, and obtaining an initial target rod position;

[0008] S2, inserting the measured control rod into the initial target rod position, and obtaining an initial reactivity difference generated in the process of inserting the measured control rod from the initial state into the initial target rod position;

[0009] S3, adjusting the core of the reactor to a supercritical state, and obtaining a segmented target rod position;

[0010] S4, inserting the measured control rod into the segmented target rod position, and obtaining a segmented reactivity difference generated in the process of inserting the measured control rod from the supercritical state into the segmented target rod position;

[0011] S5, repeatedly performing steps S3 to S4 until the measured control rod reaches the bottom of the reactor;

[0012] S6, accumulating each segmented reactivity difference obtained after each time of performing steps S3 to S4 to obtain an accumulated result;

[0013] S7, summing the accumulated result and the initial reactivity difference to obtain a reactivity value of the measured control rod.

[0014] Preferably, in the step-by-step static reactor control rod value measurement method constructed in the application, a reactivity instrument for monitoring the reactivity of the reactor is arranged in the reactor.

[0015] Preferably, in the step-by-step static reactor control rod value measurement method constructed in the application, step S1 is specifically:

[0016] S11, adjusting the core of the reactor to a critical state so that the reactor is in an initial state;

[0017] S12, lifting the measured control rod out of the core of the reactor so that the measured control rod is in an initial state;

[0018] S13, obtaining a theoretical value of the measured control rod, and calculating the initial target rod position according to the theoretical value.

[0019] Preferably, in the step-by-step static reactor control rod value measurement method constructed in the application, step S13 is specifically: obtaining a theoretical value of the measured control rod, calculating an initial expected reactivity integral value of the measured control rod from the time when the control rod is inserted outside the core of the reactor to each rod position interval according to the theoretical value, and selecting a rod position in the rod position interval where the initial expected reactivity integral value is not greater than the lower limit of the range of the reactivity instrument as the initial target rod position in this step.

[0020] Preferably, in the step-by-step static reactor control rod value measurement method constructed in the application, the following steps are performed before step S2 is performed:

[0021] S20, obtaining a first reactivity reading on the reactivity instrument when the reactor and the measured control rod are in an initial state;

[0022] Step S2 is specifically:

[0023] S21, inserting the measured control rod into the initial target rod position and making the measured control rod stay at the initial target rod position;

[0024] S22, obtaining a second reactivity reading on the reactivity instrument after the measured control rod stays at the initial target rod position for a first preset period of time;

[0025] S23, subtracting the second reactivity reading from the first reactivity reading to obtain an initial reactivity difference value.

[0026] Preferably, in the step-by-step static reactor control rod value measurement method constructed in the application, step S3 is specifically:

[0027] S31, performing a dilution operation on the reactor to adjust the core of the reactor to a supercritical state;

[0028] S32, obtaining a theoretical value of the measured control rod, and calculating the segmented target rod position according to the theoretical value.

[0029] Preferably, in the step-by-step static reactor control rod value measurement method constructed in the application, step S31 is specifically: performing the dilution operation on the reactor, and adjusting the core of the reactor to a supercritical state on the premise that the reading of the reactivity instrument is not greater than the upper limit of the measurement of the reactivity instrument.

[0030] Preferably, in the step-by-step static reactor control rod value measurement method constructed in the application, step S32 is specifically: obtaining a theoretical value of the measured control rod, calculating an expected reaction integral value of the measured control rod when inserted into each rod position interval according to the theoretical value, and selecting a rod position in the rod position interval where the expected reaction integral value is not greater than the lower limit of the reactivity instrument range as the segmented target rod position in this step.

[0031] Preferably, in the step-by-step static reactor control rod value measurement method constructed in the application, the following step is performed before step S4 is performed:

[0032] S40, obtaining a third reactivity reading on the reactivity instrument when the core of the reactor is in a supercritical state;

[0033] Step S4 is specifically:

[0034] S41, inserting the measured control rod into the segmented target rod position and making the measured control rod stay at the segmented target rod position;

[0035] S42, after waiting for the measured control rod to stay at the segmented target rod position for a second predetermined period of time, obtaining a fourth reactivity reading on the reactivity instrument at this time;

[0036] S43, subtracting the fourth reactivity reading from the third reactivity reading to obtain a segmented reactivity difference value.

[0037] Preferably, in the step-by-step static reactor control rod value measurement method constructed in the application, the method further includes the following steps:

[0038] S8, performing a boronization operation on the reactor to adjust the reactor to a critical state and remove the measured control rod from the core of the reactor, so that the reactor is in a critical state to restore the core state of the reactor.

[0039] By implementing the application, the following beneficial effects are achieved:

[0040] The application constructs a step-by-step static reactor control rod value measurement method, comprising the steps of: S1, adjusting the reactor and the measured control rod to an initial state respectively, and obtaining an initial target rod position; S2, inserting the measured control rod into the initial target rod position, and obtaining an initial reactivity difference generated in the process of the measured control rod from the initial state to the insertion into the initial target rod position; S3, adjusting the reactor core to a supercritical state, and obtaining a segmented target rod position; S4, inserting the measured control rod into the segmented target rod position, and obtaining a segmented reactivity difference generated in the process of the measured control rod from the supercritical state to the insertion into the segmented target rod position; S5, repeatedly executing the steps S3 to S4 until the measured control rod reaches the bottom of the reactor; S6, accumulating each segmented reactivity difference obtained after each execution of the steps S3 to S4 to obtain an accumulation result; and S7, summing the accumulation result and the initial reactivity difference to obtain the reactivity value of the measured control rod. The method improves the measurement accuracy of the reactivity value, reduces the measurement error, effectively solves the problem of frequent out-of-tolerance of the value measurement test results of the control rod with a smaller value, and has very important practical significance and great popularization value for nuclear power plants. BRIEF DESCRIPTION OF DRAWINGS

[0041] The application will be further described below in conjunction with the drawings and embodiments, wherein:

[0042] Figure 1 is a logic diagram of the step-by-step static reactor control rod value measurement method of the application. DETAILED DESCRIPTION

[0043] In order to have a clearer understanding of the technical features, objectives and effects of the application, the specific embodiments of the application will be described in detail below with reference to the drawings.

[0044] It should be noted that the flowchart shown in the drawings is only illustrative, and does not necessarily include all the contents and operations / steps, nor does it necessarily execute in the order described. For example, some operations / steps can be further divided, and some operations / steps can be combined or partially combined, so the actual execution order may be changed according to the actual situation.

[0045] The block diagram shown in the drawings is only a functional entity, which does not necessarily correspond to a physically independent entity. That is, these functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0046] The test process and data processing are based on a point reactor neutron kinetics model, and the neutron flux is a three-dimensional spatial distribution in the reactor core. The change of the control rod position or the continuous change of the boron concentration will affect the power distribution in the reactor, and then affect the reactivity measurement results, and finally affect the rod value measurement results. During the whole test period of the traditional boron adjustment method, the boron concentration is continuously changing. At the same time, during data processing, the reactivity change introduced during the rod movement is also converted by the intercept of the reactivity change curve during the rod movement, resulting in the influence of dynamic spatial effect during the whole boron adjustment method measurement test period. The reactivity change curve recorded on the recording paper during the test period has a certain degree of nonlinearity, which has a negative impact on the subsequent manual line drawing and increases the measurement error.

[0047] When the measured control rod value is small, the total amount of dilution or boronization of the reactor is also small, and it is difficult to establish a relatively stable dilution or boronization rate, which further leads to poor linearity of the reactivity change curve presented by the recorder, and it is easy to introduce large errors when the technician performs manual line drawing to fit a straight line and calculate the intercept.

[0048] The data processing of the traditional boron adjustment method needs to fit the reactivity change curve recorded by the recording paper into a straight line by manual line drawing, then draw a vertical line along the time midpoint of the reactivity change curve of the moving measured rod, and intersect the two ends of the fitted straight line before and after the control rod moves, respectively, to obtain the vertical line intercept value, and then convert and calculate the reactivity change amount caused by the change of the position of the measured control rod. This method will introduce errors to the measurement results due to the subjective judgment of the technician, the drawing angle and the habit.

[0049] Referring to Figure 1 The first embodiment of the present application discloses a step-by-step static reactor control rod value measurement method, which comprises the following steps:

[0050] Step S1, adjust the reactor and the measured control rod to the initial state respectively, and obtain the initial target rod position.

[0051] Step S2, insert the measured control rod into the initial target rod position, and obtain the initial reactivity difference generated in the process of inserting the measured control rod from the initial state to the initial target rod position.

[0052] Step S3, adjusting the core of the reactor to a supercritical state, and obtaining a segmented target rod position; wherein the supercritical state refers to a state of the reactor, at which time the neutron production rate in the reactor is greater than the disappearance rate, and the neutron flux level will continue to rise. The segmented target rod position can be obtained by estimation method, in actual operation, by referring to the "nuclear design report" file provided by the refueling design party, which contains the value of different control rods under the zero-power physical test condition, the theoretical data in the report can be used to estimate the segmented target rod position.

[0053] Step S4, inserting the measured control rod into the segmented target rod position, and obtaining the segmented reactivity difference generated by the measured control rod from the supercritical state to the insertion into the segmented target rod position.

[0054] Step S5, repeatedly performing steps S3 to S4 until the measured control rod reaches the bottom of the reactor.

[0055] Step S6, accumulating each segmented reactivity difference obtained after each execution of steps S3 to S4 to obtain an accumulated result.

[0056] Step S7, summing the accumulated result and the initial reactivity difference to obtain the reactivity value of the measured control rod.

[0057] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, the reactor is provided with a reactivity instrument for monitoring the reactivity of the reactor. The reactivity instrument receives the measurement current signal output from the ex-core detector, performs inverse dynamic calculation using the point reactor neutron kinetics equation, and obtains the reactivity of the reactor.

[0058] Further, the initial reactivity difference obtained in step S2 and the segmented reactivity difference obtained in step S4 are both calculated based on the reactivity reading when the reactor is in a static state, which can effectively avoid errors introduced by factors such as traditional strip dynamic spatial effect, unstable dilution rate or boronization rate, and manual line calculation, thereby improving the accuracy of the measurement.

[0059] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, step S1 specifically comprises: S11, adjusting the core of the reactor to a critical state, so that the reactor is in an initial state; S12, lifting the measured control rod outside the core of the reactor, so that the measured control rod is in an initial state; S13, obtaining the theoretical value of the measured control rod, and calculating the initial target rod position based on the theoretical value.

[0060] In the step S11 and the step S12 can be combined to perform, so that the measured control rod is taken out of the reactor core is in the vicinity of the critical state, and the reactor neutron flux is at a higher level close to the upper limit of the requirements. Thus, it can be ensured that the step S2 will be measured control rod moved to the initial target rod position, the reactor neutron flux level will not exceed the lower limit of the range of requirements. In some embodiments, the neutron flux level control range will be set in advance, the upper limit of the neutron flux is 100%, corresponding to 0.3 times the Doppler point corresponding to the neutron flux level.

[0061] Further, in the step S13 of the step-by-step static reactor control rod value measurement method disclosed in the embodiment, the theoretical value of the measured control rod is obtained, the initial expected reactivity integral value of the measured control rod from the reactor core outside to each rod position interval is calculated according to the theoretical value, and a rod position is selected as the initial target rod position in the rod position interval where the initial expected reactivity integral value is not greater than the lower limit of the range of the reactivity instrument.

[0062] For the selection of the initial target rod position X1, it is necessary to ensure that the size of the reactivity introduced into the reactor during the process of inserting the measured control rod from the initial rod position to the initial target rod position does not exceed the lower limit of the range of the reactivity instrument-100pcm, and at the same time, the initial target rod position should also meet the requirement that the reactor core will not deviate too far from the critical state after the measured control rod is inserted into the position, so as to ensure the applicability of the point reactor neutron dynamics model.

[0063] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, the following step is performed before step S2 is performed: S20, when the reactor and the measured control rod are in the initial state, obtaining the first reactivity reading on the reactivity instrument at this time. In order to obtain accurate values, the first reactivity reading is read after the reading of the reactivity instrument is stable. In some embodiments, the first reactivity reading can be read after the measured control rod is located at the initial rod position and waits for 20 seconds.

[0064] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, the step S2 is specifically: S21, inserting the measured control rod into the initial target rod position and making the measured control rod stay at the initial target rod position; S22, after the measured control rod stays at the initial target rod position for a first predetermined period of time, obtaining the second reactivity reading on the reactivity instrument at this time; S23, the second reactivity reading and the first reactivity reading are subtracted to obtain the initial reactivity difference value. The formula for obtaining the initial reactivity difference value is: Δρ0=ρ 0-2 -ρ0-1 wherein, Δρ0 is the initial reactivity difference, ρ 0-2 is the second reactivity reading, ρ 0-1 is the first reactivity reading.

[0065] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, step S3 is specifically: S31, performing a dilution operation on the reactor to adjust the core of the reactor to a supercritical state; S32, obtaining the theoretical value of the measured control rod, and calculating the segmented target rod position according to the theoretical value. Wherein, the dilution operation refers to the operation of injecting water into the reactor to reduce the boron concentration and introduce positive reactivity to the reactor.

[0066] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, step S31 is specifically: performing the dilution operation on the reactor to adjust the core of the reactor to a supercritical state, on the premise that the reading of the reactivity meter does not exceed the upper limit of the measurement of the reactivity meter.

[0067] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, step S32 is specifically: obtaining the theoretical value of the measured control rod, calculating the expected reactivity integral value of the measured control rod when inserted into each rod position interval, and selecting a rod position in the rod position interval whose expected reactivity integral value does not exceed the lower limit of the reactivity meter range as the segmented target rod position in this step.

[0068] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, before step S4 is performed, the following step is performed: S40, when the core of the reactor is in a supercritical state, obtaining a third reactivity reading on the reactivity meter at this time; in order to obtain accurate values, before reading the third reactivity reading on the reactivity meter, waiting for the reading of the reactivity meter to be stable, and then reading the third reactivity reading at this time. In some embodiments, the reactivity value displayed on the reactivity meter does not fluctuate back and forth, but stabilizes at a fixed value, and the third reactivity reading at this time is read.

[0069] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, step S4 is specifically: S41, inserting the measured control rod into the segmented target rod position and making the measured control rod stay at the segmented target rod position; S42, after the measured control rod stays at the segmented target rod position for a second preset time period, acquiring a fourth reactivity reading on the reactivity instrument at this time; and S43, subtracting the fourth reactivity reading from the third reactivity reading to obtain a segmented reactivity difference value. The formula for obtaining the initial reactivity difference value is: Δρ = ρ2- ρ1, wherein Δρ is the segmented reactivity difference value, ρ2 is the fourth reactivity reading, and ρ1 is the third reactivity reading.

[0070] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, the summing of the cumulative result and the initial reactivity difference value to obtain the reactivity value of the measured control rod in step S7 includes: ρ x = Δρ0+ Δρ1+ Δρ2+…+ Δρ n , wherein ρ x is the reactivity value of the measured control rod, Δρ0 is the initial reactivity difference value, Δρ1 is the segmented reactivity difference value obtained when step S3 to S4 is performed for the first time, Δρ2 is the segmented reactivity difference value obtained when step S3 to S4 is performed for the second time, and Δρ n is the segmented reactivity difference value obtained when step S3 to S4 is performed for the nth time, and the omitted segmented reactivity difference values between Δρ2 and Δρ n are the segmented reactivity difference values obtained when step S3 to S4 is performed for each time in between.

[0071] , wherein n≥1 and n is an integer.

[0072] Further, in the step-by-step static reactor control rod value measurement method disclosed in the embodiment, the method further includes the following step: S8, performing a boronization operation on the reactor to adjust the reactor to a critical state and remove the measured control rod from the reactor core, so that the reactor is in a critical state to restore the core state of the reactor.

[0073] The second embodiment of the present application discloses a measurement process of a step-by-step static reactor control rod value measurement method based on the first embodiment:

[0074] (1) Adjust the initial core state

[0075] Adjust all control rods to out-of-pile, so that the control rods are in the full withdrawn state and the core is in the vicinity of critical state, the neutron flux in the reactor is at a high level close to the upper limit of the requirement, to ensure that the level of the neutron flux in the reactor will not exceed the lower limit of the reactivity instrument after the measured control rod is moved in step (2). At this time, the rod position X of the measured control rod n = 225 steps, read the reactivity instrument reading in the stable state. Step is the unit of the control rod position. The control rod is divided into 225 segments in the entire axial length, and each segment represents 1 step. When the control rod is fully withdrawn from the core, it represents a rod position of 225 steps, and when the control rod is fully inserted into the core, it represents a rod position of 5 steps.

[0076] (2) Move the measured control rod

[0077] According to the theoretical value of the measured control rod, the integral value of the control rod in different rod position intervals is roughly estimated, a suitable target rod position is set, and the measured control rod is quickly inserted to the initial target rod position X1, to ensure that the reactivity introduced into the reactor does not exceed the lower limit of the reactivity instrument range -100 pcm, and also to ensure that the core does not deviate too far from the critical state, to ensure the applicability of the point reactor neutron dynamics model. Further, it is ensured that the reactivity introduced into the reactor does not exceed the lower limit of the reactivity instrument range, and is relatively close to the lower limit, to ensure that more reactivity is introduced as much as possible to reduce the number of steps of the distribution measurement.

[0078] In this embodiment, the reactivity introduced into the reactor at this time is about -90 pcm. Wait for about 20 s, and read the reactivity instrument reading after the reading is stable. Calculate the initial reactivity difference, from which the reactivity introduced into the reactor during the adjustment of the measured control rod from the initial rod position to the initial target rod position can be obtained.

[0079] (3) Adjust the core state

[0080] By dilution, the core state is adjusted to a supercritical state, and the reactivity instrument reading is stable at a state not exceeding the upper limit +100 pcm of the reactivity instrument, and the adjustment process needs to ensure that the level of the neutron flux in the reactor does not exceed the required upper and lower limit range. Read the reactivity instrument reading at this time. Further, based on risk control, the reading is controlled to be within +60 pcm.

[0081] wherein the dilution rate F is set as: In the formula, C B is the initial boron concentration;

[0082]

[0083] Through continuous dilution, the positive reactivity is continuously introduced to the reactor, and the core state is continuously monitored by the reactivity instrument during the dilution. Considering the hysteresis effect of dilution on the reactivity introduction of the reactor and the deviation of the reactivity instrument indication under dynamic conditions, when the reactivity instrument indication reaches +40 pcm, the continuous dilution needs to be stopped, and the loop needs to be waited for to reach a uniform state.

[0084] The standard for judging whether the loop reaches a uniform state is that the stabilizer and loop boron concentration sampling measurements are completed every 10 minutes. If the sampling analysis results of the stabilizer and the loop show that the boron concentration deviation between the stabilizer and the loop is less than 20 ppm for three consecutive times, it is proved that the loop has reached a uniform state.

[0085] During the continuous dilution or dilution waiting for uniformity, if the neutron flux level is about to exceed the required range of the range, the neutron flux level can be adjusted by inserting the measured control rod to ensure that the neutron flux level is within the range of the measuring instrument during the entire test period. After the short-time adjustment of the neutron flux level, the measured rod position is restored.

[0086] (4) Move the measured control rod

[0087] According to the measured control rod theoretical integral value in the "start-up physical test report" and the theoretical differential value corresponding to different rod positions, the integral value theoretical value of the control rod in different rod position intervals is calculated.

[0088] According to the integral value theoretical value corresponding to the current reactivity reading +90 pcm, the target rod position X2 of the measured control rod is calculated. The measured control rod is quickly inserted to the target rod position X2 to ensure that the reactivity of the reactor after moving the rod does not exceed the lower limit of the reactivity instrument range -100 pcm. After waiting for about 20 s, the reactivity instrument reading is read when the reactivity instrument reading is stable. Thus, the reactivity introduced by adjusting the measured control rod from rod position X1 to rod position X2 is obtained.

[0089] (5) Cycle the operations described in steps (3) and (4)

[0090] Cycle the operations of steps (3) and (4) to make the rod position of the measured control rod from X2 to X3, X4, …, X n-1 , until the rod position of the measured control rod is finally inserted to X n = 5 (at the bottom of the reactor), and the reactivity introduced by adjusting the measured control rod from rod position X2 to rod position X3, from rod position X3 to rod position X4, …, from rod position X n-1 to rod position X n is obtained, that is, a plurality of reactivity differences.

[0091] (6) Restore the core state

[0092] Boronization, adjusting the reactor to criticality, withdrawing the control rod under test from the core, and bringing the reactor to near criticality. This step can be performed selectively or after step (7).

[0093] In this step (6), the boronization rate is set to where, C B (RER) is the boron concentration in the current REA system boron tank;

[0094] The negative reactivity to be introduced to the reactor for the boronization operation is estimated to be the sum of the reactivity introduced during the process of inserting the control rod under test to the rod position X n-1 and the value of the control rod under test; n

[0095] The boron differential value ΔρC B / ΔC B at the current boron concentration is obtained from the "Start-up Physics Test Report";

[0096] The boron concentration that needs to be changed is calculated as:

[0097] Then the target boron concentration is C B (225) = C B + ΔC B

[0098] Then the amount of boron to be added is

[0099] (7) Calculate the value of the control rod under test

[0100] The value of the control rod under test is equal to the total sum of all the introduced reactivity, i.e. the cumulative sum of all the reactivity differences, during the process of the rod position of the control rod under test from X0to X1, X2, X3, X4, …, X n-1 , and finally inserting the rod position of the control rod under test to X n = 5.

[0101] Specifically, the reactivity difference when the rod position of the control rod under test from X0to X1is Δρ1, the reactivity difference when the rod position from X1to X2is Δρ2, the reactivity difference when the rod position from X2to X3is Δρ3, …, the reactivity difference when the rod position from X n-1 to X n is Δρ n . The reactivity value of the control rod under test is ρ x , ρ x = Δρ1+ Δρ2+ Δρ3+ … + Δρ n-1 + Δρ n .

[0102] ​​The step-by-step static control rod measurement method calculates the reactivity value of the measured control rod through multiple control rod insertion operations, multiple core state adjustments, and reactivity reading measurements under the static working condition of the reactor.

[0103] During the zero-power physical test process of a unit debugging and starting in a certain nuclear power plant, when the traditional boron adjustment method is used to measure the value of the D10 position control rod in the core with a small value, the measurement result error is large, and the deviation between the measured control rod value and the theoretical control rod value is up to 40 pcm, which exceeds the acceptance criteria requirement. Subsequently, the step-by-step static reactor control rod value measurement method disclosed in the present application is used to redevelop the control rod value measurement, and the final measurement result deviation from the theoretical value is reduced to 2 pcm, which fully verifies the effectiveness of the method.

[0104] By implementing the present application, the following beneficial effects are achieved:

[0105] The step-by-step static reactor control rod value measurement method disclosed in the present application can effectively avoid the influence of the traditional boron adjustment method on the rod value measurement due to dynamic space effect, unstable dilution or boronization rate, and manual line drawing calculation, improve the measurement accuracy, effectively solve the frequent result out-of-tolerance situation of the control rod value measurement with a small value, and has very important practical significance for nuclear power plants and great popularization value.

[0106] It can be understood that the above embodiments only express the preferred embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application; it should be pointed out that for ordinary skilled persons in the art, the above-mentioned embodiments or technical features can be freely combined without departing from the concept of the present application, and some deformations and improvements can be made, which belong to the protection scope of the present application, i.e. the embodiments described in "in some embodiments" can be freely combined with any of the above and below embodiments; therefore, any equivalent transformation and modification within the scope of the claims of the present application shall belong to the scope of the claims of the present application.

Claims

1. A step-wise static reactor control rod worth measurement method, characterized by, The method comprises the following steps: S1, adjusting the reactor and the measured control rod to an initial state respectively, and obtaining an initial target rod position; S2, inserting the measured control rod into the initial target rod position, and obtaining an initial reactivity difference generated in the process of inserting the measured control rod from the initial state to the initial target rod position; S3, adjusting the core of the reactor to a supercritical state, and obtaining a segmented target rod position; S4, inserting the measured control rod into the segmented target rod position, and obtaining a segmented reactivity difference generated in the process of inserting the measured control rod from the supercritical state to the segmented target rod position; S5, repeatedly performing steps S3 to S4 until the measured control rod reaches the bottom of the reactor; S6, accumulating each segmented reactivity difference obtained after each performance of steps S3 to S4 to obtain an accumulated result; S7, summing the accumulated result and the initial reactivity difference to obtain the reactivity value of the measured control rod; In step S3, the following steps are performed: S31, performing a dilution operation on the reactor to adjust the core of the reactor to a supercritical state; S32, obtaining a theoretical value of the measured control rod, and calculating the segmented target rod position according to the theoretical value; In step S32, the theoretical value of the measured control rod is obtained, the expected reactivity integral value of the measured control rod when inserted into each rod position interval is calculated according to the theoretical value, and one rod position in the rod position interval with an expected reactivity integral value not exceeding the lower limit of the reactivity instrument range is selected as the segmented target rod position in this step.

2. The step static reactor control rod value measurement method of claim 1, wherein, The reactor is provided with a reactivity instrument for monitoring the reactivity of the reactor.

3. The step static reactor control rod value measurement method of claim 2, wherein, In step S1, the following steps are performed: S11, adjusting the core of the reactor to a critical state to make the reactor in an initial state; S12, lifting the measured control rod outside the core of the reactor to make the measured control rod in an initial state; S13, obtaining a theoretical value of the measured control rod, and calculating the initial target rod position according to the theoretical value.

4. The step static reactor control rod value measurement method of claim 3, wherein, In step S13, the theoretical value of the measured control rod is obtained, the initial expected reactivity integral value of the measured control rod when inserted into each rod position interval outside the core of the reactor is calculated according to the theoretical value, and one rod position in the rod position interval with an initial expected reactivity integral value not exceeding the lower limit of the reactivity instrument range is selected as the initial target rod position in this step.

5. The step static reactor control rod value measurement method of claim 2, wherein, Before step S2 is performed, the following step is performed: S20, when the reactor and the measured control rod are in an initial state, obtaining a first reactivity reading on the reactivity instrument at this time; In step S2, the following steps are performed: S21, inserting the measured control rod into the initial target rod position and making the measured control rod stay on the initial target rod position; S22, after the measured control rod stays on the initial target rod position for a first preset time period, obtaining a second reactivity reading on the reactivity instrument at this time; S23, difference between the second reactivity reading and the first reactivity reading is obtained as the initial reactivity difference.

6. The step static reactor control rod value measurement method of claim 1, wherein, The step S31 is specifically: performing the dilution operation on the reactor, and adjusting the core of the reactor to a supercritical state under the premise that the reading of the reactivity meter does not exceed the upper limit of the measurement of the reactivity meter.

7. The step static reactor control rod value measurement method of claim 2, wherein, Before step S4 is performed, the following steps are performed: S40, when the core of the reactor is in a supercritical state, a third reactivity reading on the reactivity meter at this time is obtained; Step S4 is specifically: S41, inserting the measured control rod into the segmented target rod position and stopping the measured control rod at the segmented target rod position; S42, after the measured control rod stays at the segmented target rod position for a second preset time period, a fourth reactivity reading on the reactivity meter at this time is obtained; S43, difference between the fourth reactivity reading and the third reactivity reading is obtained as the segmented reactivity difference.

8. The step static reactor control rod value measurement method of claim 1, wherein, The method further includes the following steps: S8, performing a boronization operation on the reactor to adjust the reactor to a critical state, and taking out the measured control rod from the core of the reactor, so that the reactor is in a critical state to restore the core state of the reactor.

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