Step-by-step static reactor control rod value measurement method

Abstract

The invention discloses a step-by-step static reactor control rod value measurement method. The method comprises the following steps: enabling a reactor and a measured control rod to be in an initial state; inserting the to-be-tested control rod into the initial target rod position, and obtaining an initial reactivity difference value of the to-be-tested control rod from the initial state to the process of inserting the to-be-tested control rod into the initial target rod position; the reactor core is in a supercritical state; inserting the to-be-tested control rod into the segmented target rod position, and obtaining a segmented reactivity difference value of the to-be-tested control rod from the supercritical state to the process of inserting the to-be-tested control rod into the segmented target rod position; repeating the previous two steps until the tested control rod reaches the bottom of the reactor; the reactivity difference values of all the segments are accumulated, and an accumulation result is obtained; and summing the accumulated result and the initial reactivity difference value to obtain the reactivity value of the tested control rod. According to the method, the measurement precision is improved, the measurement error is reduced, and the problem that the value measurement test result of the control rod with relatively low value is frequently out of tolerance is effectively solved.

Description

Technical Field

[0001] The invention relates to the field of nuclear power, and in particular to a step-by-step static reactor control rod value measurement method. Background Art

[0002] Reactivity is a physical quantity that reflects the state of a nuclear reactor, characterizing the degree to which the reactor deviates from the critical state, that is, the relative offset of the effective multiplication factor K to the critical value 1. The reactivity measurement of a nuclear power plant is based on the point reactor model. The reactivity of the reactor is obtained by using a reactivity meter to receive the measurement current signal output from the external detector and performing inverse dynamic calculation using the point reactor neutron kinetic equation. Under given conditions, the absolute value of the reactivity change caused by a control rod that is completely pulled out of the core and fully inserted into the core is the control rod value.

[0003] The principle of the traditional boron adjustment method for measuring the value of control rods is: when the reactor is within the range of zero-power physical tests, the boron concentration of the reactor is continuously and uniformly diluted or boronized, and the reactivity changes introduced by the changes in boron concentration are supplemented by continuously inserting or withdrawing the control rods to ensure that the reactor is near the critical state; during this period, the reactivity instrument will reflect the reactivity changes during the entire operation on the recording paper. The technicians manually draw lines on the reactivity change curve on the recording paper to obtain the intercept value of the reactivity change during each rod movement. Using the correspondence between the recording paper grid and the reactivity channel range, the reactivity change corresponding to each rod position change is calculated. Finally, all the reactivity changes when the entire rod is fully inserted or withdrawn from the reactor are superimposed 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 range of the two is within the acceptance criteria, the measurement result is within the tolerance and the measurement test result is qualified.

[0004] In view of the problem that the traditional boron adjustment method has large measurement errors and frequent measurement test failures when measuring the value of control rods of smaller value, the boron adjustment measurement method is optimized, and a step-by-step static reactor control rod value measurement method is developed to improve measurement accuracy, reduce measurement errors, and effectively solve the problem of frequent out-of-tolerance value measurement test results of control rods of smaller value at nuclear power sites. This has very important practical significance and great promotion value for nuclear power plants. Summary of the invention

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

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

[0007] S1, adjusting the reactor and the control rod to be tested to their initial states respectively, and obtaining the initial target rod position;

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

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

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

[0011] S5, repeating steps S3 to S4 until the control rod to be tested reaches the bottom of the reactor;

[0012] S6, accumulating each of the segmented reactivity differences obtained after each execution of step S3 to step S4 to obtain an accumulation result;

[0013] S7. Sum the accumulated result and the initial reactivity difference to obtain the reactivity value of the tested control rod.

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

[0015] Preferably, in the step-by-step static reactor control rod value measurement method constructed by the present invention, 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 control rod under test to the outside of the core of the reactor, so that the control rod under test is in an initial state;

[0018] S13, obtaining the theoretical value of the control rod under test, 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 by the present invention, step S13 specifically comprises: obtaining the theoretical value of the control rod under test, calculating the initial expected reactivity integral value of the control rod under test when it is inserted from 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 does not exceed 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 by the present invention, before executing step S2, the following steps are performed:

[0021] S20, when the reactor and the control rod under test are both in an initial state, obtaining a first reactivity reading on the reactivity instrument at this time;

[0022] Step S2 is specifically as follows:

[0023] S21, inserting the control rod under test to the initial target rod position, and making the control rod under test stay at the initial target rod position;

[0024] S22, waiting for the control rod under test to stay at the initial target rod position for a first preset period of time, and obtaining a second reactivity reading on the reactivity instrument at this time;

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

[0026] Preferably, in the step-by-step static reactor control rod value measurement method constructed by the present invention, 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 the theoretical value of the control rod under test, 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 by the present invention, step S31 specifically comprises: 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 measurement upper limit of the reactivity meter.

[0030] Preferably, in the step-by-step static reactor control rod value measurement method constructed by the present invention, step S32 is specifically: obtaining the theoretical value of the control rod under test, calculating the expected reactivity integral value when the control rod under test is inserted into each rod position interval according to the theoretical value, and selecting a rod position in the rod position interval where the expected reactivity integral value does not exceed 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 by the present invention, before executing step S4, the following steps are performed:

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

[0033] Step S4 is specifically as follows:

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

[0035] S42, waiting for the control rod under test to stay at the segmented target rod position for a second preset time period, and 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 the segmented reactivity difference value.

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

[0038] S8. Perform a boronization operation on the reactor to adjust the reactor to a critical state, and take the control rod under test out of 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 present invention, the following beneficial effects are achieved:

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

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0042] Figure 1 It is a logical schematic diagram of the step-by-step static reactor control rod value measurement method of the present invention. DETAILED DESCRIPTION

[0043] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0044] It should be noted that the flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor do they have to be executed in the order described. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0045] The block diagrams shown in the accompanying drawings are only functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software form, 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 the point reactor neutron kinetic model, and the neutron flux is distributed in three-dimensional space in the core. Changes in the control rod position or continuous changes in boron concentration will affect the power distribution inside the reactor, which in turn affects the reactivity measurement results, and ultimately affects the rod value measurement results. During the entire test period of the traditional boron adjustment method, the boron concentration continues to change; at the same time, when processing data, it is also necessary to convert the intercept of the reactivity change curve during the rod moving period to obtain the reactivity change introduced during the rod moving period, resulting in the entire boron adjustment method measurement test period being affected by the dynamic spatial effect, causing the reactivity change curve presented on the recording paper during the test to have a certain degree of nonlinearity, which has a negative impact on the subsequent manual marking of data processing and increases the measurement error.

[0047] When the value of the control rod being tested is small, the total amount of dilution or boronization of the reactor is also small, making it 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. It is easy to introduce large errors when technicians manually draw lines to fit the straight line and calculate the intercept.

[0048] The traditional boron adjustment method data processing requires that the reactivity change curve recorded on the recording paper be fitted into a straight line by manual drawing, and then a vertical line is drawn along the time midpoint of the reactivity change curve of the moving rod to be measured, and the vertical line is intersected with the two ends of the fitting straight line before and after the control rod is moved, and the vertical line intercept value is obtained, and then the reactivity change caused by the rod position change of the measured control rod is obtained by conversion calculation. This method will introduce errors to the measurement results due to the subjective judgment, drawing perspective and habits of technicians.

[0049] See also Figure 1 The first embodiment of the present invention discloses a step-by-step static reactor control rod value measurement method, the method comprising the following steps:

[0050] Step S1, adjusting the reactor and the control rod to be tested to their initial states respectively, and obtaining the initial target rod position.

[0051] Step S2: inserting the control rod under test to the initial target rod position, and obtaining an initial reactivity difference value generated in the process of the control rod under test from the initial state to the insertion into the initial target rod position.

[0052] Step S3, adjust the core of the reactor to a supercritical state, and obtain the segmented target rod position; wherein the supercritical state refers to a state of the reactor, at which 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 relying on an estimation method. In actual operation, by consulting the "Nuclear Design Report" file provided by the refueling designer, which contains the value of different control rods under zero-power physical test conditions, the segmented target rod position can be estimated based on the theoretical data in the report.

[0053] Step S4: inserting the control rod under test into the segmented target rod position, and obtaining the segmented reactivity difference generated in the process of the control rod under test from the supercritical state to the insertion into the segmented target rod position.

[0054] Step S5, repeating steps S3 to S4 until the control rod under test reaches the bottom of the reactor.

[0055] Step S6, accumulating each of the segmented reactivity differences obtained after each execution of step S3 to step S4 to obtain an accumulation result.

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

[0057] Furthermore, in the step-by-step static reactor control rod value measurement method disclosed in this embodiment, a reactivity meter for monitoring the reactor is provided in the reactor. The reactivity meter receives the measurement current signal output from the external detector, performs inverse dynamic calculation using the point reactor neutron kinetic equation, and obtains the reactivity of the reactor.

[0058] Furthermore, the initial reactivity difference obtained in step S2 and the segmented reactivity difference obtained in step S4 are both calculated based on the reactivity readings when the reactor is in static conditions. This can effectively avoid errors introduced into the control rod value measurement due to factors such as the dynamic spatial effect of traditional rod readings, unstable dilution rate or boronization rate, and manual line calculation, thereby improving the measurement accuracy.

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

[0060] Among them, step S11 and step S12 can be combined and executed so that when all the control rods under test are taken out of the reactor, the core of the reactor is in a critical state and the neutron flux of the reactor is at a high level close to the upper limit of the requirement. Thus, it can be ensured that when the control rods under test are moved to the initial target rod position in step S2, the neutron flux level of the reactor will not exceed the lower limit requirement range. In some embodiments, the neutron flux level control range will be set in advance, and the upper limit of the neutron flux is 100%, corresponding to the neutron flux level corresponding to 0.3 times the Doppler point.

[0061] Furthermore, in the step-by-step static reactor control rod value measurement method disclosed in the present embodiment, step S13 specifically comprises: obtaining the theoretical value of the control rod under test, calculating the initial expected reactivity integral value of the control rod under test when it is inserted from 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 does not exceed the lower limit of the range of the reactivity instrument as the initial target rod position in this step.

[0062] For the initial target stick position X 1 The selection of the control rod should ensure that the reactivity introduced into the reactor during the insertion of the control rod from the initial rod position to the initial target rod position does not exceed the lower limit of the reactivity instrument range of -100 pcm. At the same time, the initial target rod position should also ensure that after the control rod is inserted into place, the core of the reactor will not deviate too far from the critical state, so as to ensure the applicability of the point reactor neutron kinetic model.

[0063] Furthermore, in the step-by-step static reactor control rod value measurement method disclosed in this embodiment, before executing step S2, the following steps are executed: S20, when the reactor and the control rod to be tested are both in the initial state, obtaining the first reactivity reading on the reactivity meter at this time. In order to obtain an accurate value, before reading the first reactivity reading on the reactivity meter, wait for the reading of the reactivity meter to stabilize before reading the first reactivity reading at this time. In some embodiments, the first reactivity reading at this time can be read after waiting for 20 seconds for the control rod to be tested to be in the initial rod position.

[0064] Further, in the step-by-step static reactor control rod value measurement method disclosed in this embodiment, step S2 is specifically as follows: S21, inserting the control rod to be tested into the initial target rod position, and making the control rod to be tested stay at the initial target rod position; S22, waiting for the control rod to be tested to stay at the initial target rod position for a first preset time period, and obtaining a second reactivity reading on the reactivity instrument at this time; S23, subtracting the second reactivity reading from the first reactivity reading to obtain the initial reactivity difference. The formula for obtaining the initial reactivity difference is: Δρ0 =ρ 0-2 -ρ 0-1 , where Δρ 0 is the initial reactivity difference, ρ 0-2 is the second reactivity reading, ρ 0-1 This is the first reactivity reading.

[0065] Further, in the step-by-step static reactor control rod value measurement method disclosed in this embodiment, step S3 is specifically as follows: 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 control rod under test, and calculating the segmented target rod position according to the theoretical value. The dilution operation refers to the operation of injecting water into the reactor to reduce the boron concentration and introduce positive reactivity into the reactor.

[0066] Furthermore, in the step-by-step static reactor control rod value measurement method disclosed in this embodiment, step S31 specifically includes: 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 measurement upper limit of the reactivity meter.

[0067] Furthermore, in the step-by-step static reactor control rod value measurement method disclosed in the present embodiment, step S32 specifically comprises: obtaining the theoretical value of the control rod under test, calculating the expected reactivity integral value when the control rod under test is inserted into each rod position interval according to the theoretical value, and selecting a rod position in the rod position interval where the expected reactivity integral value does not exceed the lower limit of the reactivity instrument 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 this embodiment, before executing step S4, the following steps are executed: S40, when the core of the reactor is in a supercritical state, obtain the third reactivity reading on the reactivity meter at this time; in order to obtain an accurate value, before reading the third reactivity reading on the reactivity meter, wait for the reading of the reactivity meter to stabilize, and then read the third reactivity reading at this time. In some embodiments, the reactivity value displayed on the reactivity meter does not jump 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 this embodiment, step S4 is specifically as follows: S41, inserting the control rod to be tested into the segmented target rod position, and making the control rod to be tested stay at the segmented target rod position; S42, waiting for the control rod to be tested to stay at the segmented target rod position for a second preset time period, and obtaining the fourth reactivity reading on the reactivity instrument at this time; S43, subtracting the fourth reactivity reading from the third reactivity reading to obtain the segmented reactivity difference. The formula for obtaining the initial reactivity difference is: Δρ=ρ 2 -ρ 1 , where Δρ is the difference in segmented reactivity, ρ 2 is the fourth reactivity reading, ρ 1 is the third reactivity reading.

[0070] Further, in the step-by-step static reactor control rod value measurement method disclosed in this embodiment, in step S7, the cumulative result and the initial reactivity difference are summed to obtain the reactivity value of the measured control rod, which includes: ρ x =Δρ 0 +Δρ 1 +Δρ 2 +…+Δρ n , where ρ x is the reactivity value of the control rod under test, Δρ 0 is the initial reactivity difference, Δρ 1 is the difference in the segmented reactivity obtained when steps S3 to S4 are performed for the first time, Δρ 2 is the difference in segmental reactivity obtained when steps S3 to S4 are performed for the second time ... Δρ n is the difference in segmented reactivity obtained when steps S3 to S4 are performed for the nth time, Δρ 2 With Δρ n Omitted are the segmented reactivity differences obtained each time steps S3 to S4 are performed.

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

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

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

[0074] (1) Adjusting the initial core state

[0075] All control rods are adjusted outside the reactor so that they are all out of the core and the core is near criticality. The reactor neutron flux is at a high level close to the upper limit required to ensure that after the control rods under test are moved in step (2), the reactor neutron flux level will not exceed the lower limit required by the reactivity instrument. n = 225 steps, read the instrument reading of the reactivity instrument in a stable state. Step is the unit of control rod position. The entire axial length of the control rod is divided into 225 sections, each section represents 1 step. When the control rod is fully pulled out of the core, it represents that the rod position is 225 steps. When the control rod is fully inserted into the core, it represents that the rod position is 5 steps.

[0076] (2) Move the control rod under test

[0077] According to the theoretical value of the control rod under test, roughly estimate the integral value of the control rod in different rod position intervals, set an appropriate target rod position, and quickly insert the control rod under test to the initial target rod position X 1 , ensuring that the reactivity introduced into the reactor does not exceed the lower limit of the reactivity instrument range -100pcm, while also ensuring that the core does not deviate too far from the critical state, ensuring the applicability of the point reactor neutron kinetic model. Further, ensuring that the reactivity introduced into the reactor does not exceed the lower limit of the reactivity instrument range, while being relatively close to the lower limit, ensuring that as much reactivity as possible is introduced to minimize the number of steps in the distributed measurement.

[0078] In this embodiment, the reactivity introduced into the reactor at this time is about -90pcm. Wait for about 20 seconds, and after the reactivity meter reading is stable, read the reactivity meter reading at this time. Calculate the initial reactivity difference, and thus obtain the reactivity introduced into the reactor during the process of adjusting the control rod under test from the initial rod position to the initial target rod position.

[0079] (3) Adjusting the core status

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

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

[0082]

[0083] Positive reactivity is continuously introduced into the reactor through continuous dilution, during which the core state is continuously monitored through the reactivity meter indication. Taking into account the lag effect of dilution on reactor reactivity and the deviation of the reactivity meter indication under dynamic conditions, when the reactivity meter indication reaches +40pcm, continuous dilution must be stopped and the loop must wait for a uniform state.

[0084] The criterion for judging whether the circuit has reached a uniform state is to complete a sampling measurement of the boron concentration of the voltage stabilizer and the circuit every 10 minutes. If the results of three consecutive sampling analyses show that the deviation of the boron concentration between the voltage stabilizer and the circuit is less than 20ppm, it proves that the circuit has reached a uniform state.

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

[0086] (4) Move the control rod under test

[0087] According to the theoretical integral value of the control rod under test in the "Start-up Physical Test Report" and the theoretical differential value corresponding to different rod positions, the theoretical value of the control rod integral value in different rod position intervals is calculated.

[0088] According to the theoretical value of the integral value corresponding to the current reactivity reading + 90pcm, the target rod position X of the control rod to be tested is calculated. 2 . Quickly insert the control rod to the target rod position X 2 , to ensure that the reactivity of the reactor after the rod is moved does not exceed the lower limit of the reactivity meter range of -100pcm. Wait for about 20s, and read the reactivity meter reading after the reactivity meter reading stabilizes. 1 Adjust to stick position X 2 Introduced reactivity.

[0089] (5) Loop through the operations from step (3) to step (4)

[0090] Execute steps (3) to (4) repeatedly, so that the position of the control rod under test changes from X to 2 Arrive at X 3 , X 4 ,……,X n-1 Until the control rod to be tested is inserted down to X n = 5 steps (at the bottom of the reactor), the control rod under test is obtained from the rod position X 2 Adjust to stick position X 3 , by the rod position X 3 Adjust to stick position X4 , ..., by the stick position X n-1 Adjust to stick position X n The reactivity introduced, i.e., multiple reactivity differences.

[0091] (6) Restoring the core status

[0092] By boronization, the reactor is adjusted to a critical state, the control rod to be tested is taken out of the reactor, and the reactor is placed in a near-critical state. This step can be performed selectively or after step (7).

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

[0094] It is estimated that the negative reactivity that needs to be introduced into the reactor during the boronization operation is: n-1 Insert to rod position X n The reactivity introduced during the process is added to the value of the control rod being measured;

[0095] Query the boron differential value ΔρC at the current boron concentration through the "Startup Physical Test Report" B / ΔC B ;

[0096] Calculate the required change in boron concentration:

[0097] The target boron concentration is C B (225) = C B +ΔC B ;

[0098] Boron amount

[0099] (7) Calculate the value of the control rod being tested

[0100] The value of the control rod under test is equal to the position of the control rod under test from X 0 Arrive at X 1 , X 2 , X 3 , X 4 ,……,X n-1 Until the control rod to be tested is inserted down to X n = The cumulative sum of all introduced reactivities obtained during the 5-step process, i.e., all reactivity differences.

[0101] Specifically, the rod position of the control rod to be measured is from X 0 Arrive at X 1 The reactivity difference is Δρ1 , from X 1 Arrive at X 2 The reactivity difference is Δρ 2 , from X 2 Arrive at X 3 The reactivity difference is Δρ 3 , ..., from X n-1 Arrive at X n The reactivity difference is Δρ n The reactivity value of the control rod under test is ρ x , ρ x =Δρ 1 +Δρ 2 +Δρ 3 +……+Δρ n-1 +Δρ n .

[0102] The above-mentioned step-by-step static control rod measurement method calculates the reactivity value of the measured control rod through multiple control rod insertion operations, multiple dilution core state adjustments, and reactivity reading measurements when the reactor is in a static condition.

[0103] During the commissioning and startup of a unit in a nuclear power plant, when the traditional boron adjustment method was used to measure the value of the control rod at the D10 position of the core with a relatively small value, a large measurement error occurred. The deviation between the measured control rod value and the theoretical control rod value reached 40pcm, which exceeded the acceptance criteria. Subsequently, the step-by-step static reactor control rod value measurement method disclosed in the present invention was used to re-measure the control rod value. The final measurement result and the theoretical value deviation were reduced to 2pcm, which fully verified the effectiveness of the method.

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

[0105] The invention discloses a step-by-step static reactor control rod value measurement method, which 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 calculation, improve the measurement accuracy, and effectively solve the problem of frequent out-of-tolerance results in the value measurement test of control rods with smaller values. It has very important practical significance for nuclear power plants and has great promotion value.

[0106] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, without departing from the concept of the present invention, the above embodiments or technical features can be freely combined, and several deformations and improvements can be made, which all belong to the protection scope of the present invention, that is, the embodiments described in "some embodiments" can be freely combined with any of the above and below embodiments. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A step-by-step static reactor control rod value measurement method, characterized in that: The method comprises the following steps: S1, adjusting the reactor and the control rod to be tested to their initial states respectively, and obtaining the initial target rod position; S2, inserting the control rod under test to the initial target rod position, and obtaining an initial reactivity difference value generated in the process of the control rod under test from the initial state to the insertion into the initial target rod position; S3, adjusting the core of the reactor to a supercritical state, and obtaining segmented target rod positions; S4, inserting the control rod under test into the segmented target rod position, and obtaining the segmented reactivity difference generated in the process of the control rod under test from the supercritical state to the insertion into the segmented target rod position; S5, repeating steps S3 to S4 until the control rod to be tested reaches the bottom of the reactor; S6, accumulating each of the segmented reactivity differences obtained after each execution of step S3 to step S4 to obtain an accumulation result; S7. Sum the accumulated result and the initial reactivity difference to obtain the reactivity value of the tested control rod.

2. The step-by-step static reactor control rod value measurement method according to claim 1, characterized in that: The reactor is provided with a reactivity instrument for monitoring the reactor.

3. The step-by-step static reactor control rod value measurement method according to claim 2, characterized in that: Step S1 is specifically as follows: S11, adjusting the core of the reactor to a critical state so that the reactor is in an initial state; S12, lifting the control rod under test to the outside of the core of the reactor, so that the control rod under test is in an initial state; S13, obtaining the theoretical value of the control rod under test, and calculating the initial target rod position according to the theoretical value.

4. The step-by-step static reactor control rod value measurement method according to claim 3, characterized in that: Step S13 specifically includes: obtaining the theoretical value of the control rod under test, calculating the initial expected reactivity integral value when the control rod under test is inserted from the outside of the reactor core 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 does not exceed the lower limit of the range of the reactivity instrument as the initial target rod position in this step.

5. The step-by-step static reactor control rod value measurement method according to claim 2, characterized in that: Before executing step S2, perform the following steps: S20, when the reactor and the control rod under test are both in an initial state, obtaining a first reactivity reading on the reactivity instrument at this time; Step S2 is specifically as follows: S21, inserting the control rod under test to the initial target rod position, and making the control rod under test stay at the initial target rod position; S22, waiting for the control rod under test to stay at the initial target rod position for a first preset period of time, and obtaining a second reactivity reading on the reactivity instrument at this time; S23, subtracting the second reactivity reading from the first reactivity reading to obtain the initial reactivity difference value.

6. The step-by-step static reactor control rod value measurement method according to claim 2, characterized in that: Step S3 is specifically as follows: 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 control rod under test, and calculating the segmented target rod position according to the theoretical value.

7. The step-by-step static reactor control rod value measurement method according to claim 6, characterized in that: Step S31 specifically includes: 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 instrument does not exceed the measurement upper limit of the reactivity instrument.

8. The step-by-step static reactor control rod value measurement method according to claim 6, characterized in that: Step S32 specifically includes: obtaining the theoretical value of the control rod under test, calculating the expected reactivity integral value when the control rod under test is inserted into each rod position interval according to the theoretical value, and selecting a rod position in the rod position interval where the expected reactivity integral value does not exceed the lower limit of the reactivity instrument range as the segmented target rod position in this step.

9. The step-by-step static reactor control rod value measurement method according to claim 2, characterized in that: Before executing step S4, the following steps are performed: S40, when the core of the reactor is in a supercritical state, obtaining a third reactivity reading on the reactivity instrument at this time; Step S4 is specifically as follows: S41, inserting the control rod to be tested into the segmented target rod position, and making the control rod to be tested stay at the segmented target rod position; S42, waiting for the control rod under test to stay at the segmented target rod position for a second preset time period, and obtaining a fourth reactivity reading on the reactivity instrument at this time; S43, subtracting the fourth reactivity reading from the third reactivity reading to obtain the segmented reactivity difference value.

10. The step-by-step static reactor control rod value measurement method according to claim 1, characterized in that: The method further comprises the following steps: S8. Perform a boronization operation on the reactor to adjust the reactor to a critical state, and take the control rod under test out of the core of the reactor so that the reactor is in a critical state to restore the core state of the reactor.

Images