A method for checking and verifying a reactor dynamic parameter symmetric group rod optimization fitting strategy

Abstract

The present application belongs to the technical field of nuclear reactor physics test, and particularly relates to a reactor dynamic parameter symmetric group rod optimization fitting strategy checking and verifying method, step one: based on the data reliability checking and measuring of the core symmetry, a group of original data which can be checked mutually is obtained; step two: based on the fitting process optimization and verification of the symmetric data, the fitting strategy which can reduce the subjective sensitivity and can be self-verified is implemented by using the checked reliable data. The present application solves the technical problems of low data reliability and high fitting sensitivity in the traditional extrapolation method by the cooperative measurement and optimization fitting strategy of the symmetric group rod.

Description

Technical Field

[0001] This invention belongs to the field of nuclear reactor physics testing technology, specifically relating to a verification method for a symmetrical rod assembly optimization fitting strategy for reactor dynamic parameters. By using a symmetrical rod assembly collaborative measurement and optimization fitting strategy, it solves the technical problems of low data reliability and high fitting sensitivity in traditional extrapolation methods. Background Technology

[0002] Importance of reactor dynamic characteristic parameters in reactor physics experimental verification and validation measurements The expression is: It is a crucial bridge connecting the effective delayed neutron fraction and the transient neutron lifetime, and its accurate measurement is an indispensable experimental benchmark for reactor physics design verification and safety analysis. The effective delayed neutron share represents the proportion of delayed neutrons in the total neutron source; Reactivity indicates the degree to which a system deviates from its critical state; Neutron effective lifetime represents the average time from the generation of a fission neutron to its subsequent fission. This formula reflects... Its central position in the core dynamics model: it integrates neutron lifetime ( Slow-released neutron effect ( ) and system reactivity ( The combined effects of ) through precise measurement Further verification and validation of other dynamic parameters can be performed.

[0003] Dynamic parameters Measurement Principle Analysis: Characteristic Parameters Commonly used measurement methods include the Rossi-α method, the Feynman method, and the pulse source method. The derivation originates from the nth-order system eigenvalues ​​of reactor neutron spacetime dynamics. , with system eigenvalues Specifically referring to the eigenvalues, or fundamental modes, of the 0th-order system. The difference is, It is also the equilibrium point within the instantaneous neutron reactor under the slow-release critical state, according to The expression: (1) in: Let be the eigenvalues ​​of the nth-order system, with dimensions (s). -1 ); The geometric curvature is of order n; The neutron diffusion area; For diffusion time; For infinite media multiplication factor; For the total delayed neutron emission share; , Let represent the fraction and decay constant of the i-th group of slow-emitting neutrons.

[0004] (1) The first term represents the system state, and the second term is the intercept term. The numerator of the first term indicates the three states of the system: critical, subcritical, and supercritical; the intercept of the second term is a coefficient related to the delayed neutron fraction. When the system is in the critical state, the intercept is the dynamic parameter of the instantaneous neutrons in the delayed critical state. .

[0005] (2) From equation (2), we can see that the dynamic parameters under critical conditions are... Coupled with instantaneous neutrons First harmonic and The delayed neutron emission characteristics of the reactor are in a dynamic equilibrium under high background neutron flux within the reactor, and the critical state can be directly measured. Distinguishing neutrons from multiple decay chains under high background conditions is necessary. For example, the Rossi-α method requires high detector sensitivity and interference resistance, while the Feynman method requires long-term data acquisition and is sensitive to background statistical errors, such as when measuring on the UTR-KINKI device. The gamma background can be overestimated by up to 24%. The pulse source method is characterized by its intuitiveness and strong anti-interference capability; however, in the delayed critical state, it is difficult to distinguish between delayed and transient neutrons from a measurement perspective. Generally, different values ​​near the critical point are used to differentiate them. The measured values ​​were fitted to obtain Extrapolation fitting involves different subcritical states. To the critical point of slow onset Excessive.

[0006] Express the numerator of the intercept term in equation (1) as follows: Considering the change in the sub-absorption cross section during the rod lifting process and axial variation of curvature coefficient Thus, an approximate relationship (3) is obtained for the attenuation coefficient as a function of the control rod insertion depth. The factors influencing the curve are quite complex. In addition to changes in delayed neutron fractions The influence of the added value coefficient is also related to factors such as the non-uniformity of the differential value of the control rod and marginal effects, while the change in the absorption cross section... and curvature change It is a comprehensive effect, the specific form of which is related to factors such as the value efficiency of the control rods and the interference effect between the rods. The curve represents the macroscopic effects of the longitudinal distribution and axial variation of neutron flux within the reactor.

[0007] (3) Express the intercept term in equation (1) as Introducing the value-added coefficient as it changes with reactivity And the change of absorption cross section with reactivity From this, we can obtain the relationship between the attenuation coefficient and the change in reactivity (4). Essentially, it is a linear relationship between the subcritical reactivity value and the transient neutron fundamental frequency coefficient, measured by changes in reactivity. It is a relatively simple linear extrapolation relationship. Considering the neutron rate fluctuations under deep subcritical conditions, this linear relationship is applicable only under intermediate subcritical conditions.

[0008] (4) Dynamic parameters Difficulties encountered in fit of nearest-neighbor extrapolation: The above analysis shows that fitting near the nearest point faces multiple influencing factors. These factors macroscopically manifest as the radial flattening distribution and axial gradient variation of neutron flux. Therefore, the fitting curve near the nearest point is the result of the combined effects of neutron flux within the reactor core, and is related to the actual distribution of neutron flux in different reactor cores, making it an engineering measurement problem. Dynamic parameters The difficulties encountered in near-term extrapolation fitting are: the measurement data itself lacks a verification mechanism; traditional methods only measure a single control bar. Rod position data is susceptible to factors such as local core disturbances and detector response drift, posing a risk of undetected systematic or gross errors, and lacks verification of data reliability. The extrapolation fitting process is highly sensitive, and the selection of data ranges is largely subjective. The acquisition depends on the - or - Mathematical fitting of curves. The fitting results are extremely sensitive to the chosen approximation formula (linear, exponential, polynomial, etc.) and the data interval used in the fitting. For curves of varying shapes, there is a lack of objective standards for choosing the correct formula and interval, leading to discrete results from different analysts or different choices. This value makes the verification itself unreliable.

[0009] Therefore, there is an urgent need in this field for an innovative method that can simultaneously perform built-in verification and validation of measurement data and the fitting process to meet the requirements. Extrapolation fitting has universality across different stack types, while effectively improving the accuracy and confidence of the measurement results. Summary of the Invention

[0010] The purpose of this invention is to provide a verification method for the optimization fitting strategy of symmetrical rod assembly for reactor dynamic parameters. The method uses the measurement and comparison of symmetrical rod assembly as a data verification means, and uses the verified data to guide the optimization fitting. Finally, the consistency of the multi-path fitting results is used to verify the overall measurement and analysis process, forming an interlocking strategy system, which solves the shortcomings of traditional single rod fitting.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A verification method for a symmetric rod-based optimization fitting strategy for reactor dynamic parameters: Step 1: Based on the reliability verification measurement of core symmetry, obtain a set of original data that can be mutually verified; Step 2: Based on the symmetric data, optimize and verify the fitting process, and use the verified reliable data to implement a fitting strategy that can reduce subjective sensitivity and is self-verifiable.

[0012] Step one specifically comprises: S101: After the reactor reaches criticality and the flux is flattened, a pair of control rods H1 and H2 with geometric symmetry within the core are selected and defined as a symmetry check rod group; S102: Each rod in the symmetry rod group is independently and completely checked. - Bar position sequence measurement involves fixing all other bars, changing the position of a single symmetrical bar, and measuring its position. Value; S103: Perform cross-checking of data self-consistency, and combine the measurements obtained from the two symmetrical bars. - The curves at the rod positions are compared. According to the principle of core physics symmetry, these two curves should ideally overlap completely. In actual operation, the overall reliability of this measurement activity is verified by calculating the deviation of the two curves at the corresponding rod positions or the overall degree of agreement.

[0013] If the deviation exceeds the reasonable range of the engineering, it indicates that there is an abnormality in the measurement system or the core condition, and the data is unreliable. The cause must be investigated and the measurement must be repeated. If the deviation is within the preset tolerance, the measurement data is determined to be valid and reliable, and the next step of analysis can be carried out.

[0014] Step two specifically includes: S201: Collaborative optimization fitting interval selection. Based on the two curves verified in step one, their morphological consistency is comprehensively analyzed, and regions where both curves exhibit significant nonlinearity, jumps, or deviations are eliminated. A data interval where both curves perform well and are consistent is selected as the common fitting interval; S202: Multi-path complementary fitting verification is implemented. Within the selected optimization interval, at least two extrapolation paths with different principles are used for fitting: Path A: direct curve fitting; - The rod-position relationship is fitted using a direct function, and path B linear theory fitting is used: the rod position is converted into reactivity using the control rod value curve. , build - The relationship, based on reactor neutron dynamics theory, is linear at an appropriate subcritical degree. This linear relationship is fitted and extrapolated to... =0, thus obtaining subscript B Representation and path B Linear theoretical fitting of reactor dynamic characteristic parameters corresponding to control rods S203: Perform consistency verification and final determination of the fitting results, comparing multiple results obtained from different paths A and B and different symmetric rods 1 and 2. Forecast , , These values ​​originate from the same physical essence. However, because the measurement and fitting paths are independent, they form a cross-validation network for the fitting process and the final result.

[0015] The deviated areas include the boundary effect zone when the rod is positioned too deep.

[0016] The type of fitting function is not fixed in advance, but is adaptively selected based on the common morphological characteristics exhibited by the two symmetrical curves within the optimization interval.

[0017] If both curves exhibit an exponential decay trend within this interval, then an exponential fitting method is uniformly used. This method is applied to the independent data of both bars and extrapolated to obtain the desired results. and subscript A1 and A2 This represents the direct curve fitting of the two symmetrical bars corresponding to path A. .

[0018] If these estimates are highly consistent statistically, it strongly validates the correctness and robustness of the entire measurement and fitting process, ultimately... Take the average or optimal estimate of these values; if a certain estimate deviates significantly, trace its corresponding fitting path or individual data point, analyze and remove it to ensure that the final result is not affected by abnormal paths.

[0019] High consistency is defined as a standard deviation less than a preset threshold of 1.5 s. -1 .

[0020] The process also includes step three: systematic verification of multiple sets of symmetric bars. Multiple different sets of symmetric bars are selected within the same core load, and steps one and two are executed in parallel. Finally, the results of all independent verification sets are synthesized to provide a more universal and statistically significant assessment. The final value and its uncertainty.

[0021] The beneficial effects achieved by this invention are as follows: The symmetric rod optimization fitting strategy of this invention is for reactor dynamic parameters Improvements to the verification and validation process: It pioneered an internal verification mechanism for measurement data: by comparing the measurement curves using symmetrical bars, it achieved the verification of... Proactive and objective verification of the reliability of raw measurement data moves data quality control from post-evaluation to process control, reducing the risk of extrapolating from unreliable data.

[0022] The method optimizes and self-verifies the fitting process: it collaboratively determines the optimal fitting interval using symmetric data and employs multi-path independent fitting, transforming the extrapolation process from a single-path guess relying on subjective experience to a multi-path collaborative optimization and verification based on data commonalities and theory. This significantly reduces sensitivity to specific formulas and intervals, greatly improving the robustness of the method.

[0023] Integrating verification into the method body: This method outputs more than just a single... The numerical value is a reliable result, backed by both data verification and process validation. Its relatively small result dispersion (e.g., ±1.15 s) -1 This itself is a powerful proof of the method's effectiveness, and it aligns with the fundamental experimental purpose of verification.

[0024] A standardized and scalable methodology has been developed: the strategy has clear steps, rigorous logic, does not rely on prior knowledge of specific curve shapes, can adaptively handle different curve types under various core loading conditions, and has strong engineering applicability and promotion value. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the principle of symmetrical rod measurement and data verification in this invention; Figure 2 A schematic diagram of data self-consistency verification and collaborative optimization fitting interval selection for a symmetric bar group (H1, H2) with a single core; Figure 3 A schematic diagram of the data self-consistency verification and collaborative optimization fitting interval selection for loading two core symmetric bar groups (K1, K2); Figure 4 A schematic diagram of the data self-consistency verification and collaborative optimization fitting interval selection for loading 3-core symmetric bar groups (G1, G2); Figure 5 To use path B ( - A schematic diagram of extrapolating the same set of verification data using linear fitting. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] The technical solution of this invention revolves around a symmetrical bar-based optimized fitting strategy, which is a complete methodology integrating data acquisition and verification with the fitting process validation. Its core objective is to proactively verify and validate the reliability of measurement data and the robustness of fitting extrapolation through a built-in, systematic strategy, thereby outputting a reliable result that has undergone multiple cross-validations. Value. The specific steps are as follows: Step 1: Data reliability verification measurement based on core symmetry. The core objective of this step is to obtain a set of raw data that can be cross-checked.

[0028] S101: After the reactor reaches criticality and the flux is flattened, a pair of control rods with geometric symmetry in the core (such as H1 and H2) are deliberately selected and defined as the "symmetry check rod group".

[0029] S102: Perform independent and complete analysis on each bar in the symmetrical bar group. - Bar position sequence measurement. This involves fixing all other bars, individually changing the position of one symmetrical bar, and measuring its position. value.

[0030] S103: Perform cross-checking of data self-consistency. This involves measuring the data from two symmetrical rods. - The rod position curves are compared. According to the principle of core physics symmetry, these two curves should ideally coincide perfectly. In practice, the overall reliability of the measurement activity is verified by calculating the deviation or overall fit of the two curves at corresponding rod positions. If the deviation exceeds the reasonable engineering range, it indicates an anomaly in the measurement system or core condition, and the data is unreliable; the cause must be investigated and the measurement repeated. If the deviation is within the preset tolerance, the measurement data is deemed valid and reliable, and the next step of analysis can proceed. This step is the first of its kind in... A "data verification" step was introduced into the measurement process.

[0031] Step Two: Optimization and Validation of the Fitting Process Based on Symmetrical Data. The core objective of this step is to implement a fitting strategy that reduces subjective sensitivity and is self-verifiable, using verified and reliable data.

[0032] S201: Selection of the Collaborative Optimization Fitting Interval. Based on the two curves validated in Step 1, their morphological consistency is comprehensively analyzed. Regions where both curves exhibit significant nonlinearity, jumps, or deviations (such as the boundary effect region when the rod is too deep) are eliminated. A data interval where both curves perform well and are consistent is selected as the common fitting interval. This selection is based on the data's own performance, rather than subjective judgment.

[0033] S202: Perform multi-path complementary fitting verification. Within the selected optimization interval, use at least two extrapolation paths with different principles for fitting: Path A (direct curve fitting): for... - The relationship between the bars is fitted using a direct function. The type of fitting function (e.g., exponential, linear, low-order polynomial) is not predetermined but adaptively selected based on the common morphological characteristics exhibited by the two symmetrical curves within the optimization interval. For example, if both curves show an exponential decay trend within this interval, an exponential fitting is uniformly used. The independent data for each bar are then extrapolated using this function to obtain... and (Here, subscripts A1 and A2 represent the direct curve fitting of the two symmetrical bars corresponding to path A, respectively.) Path B (Linear Theoretical Fit): Using the control rod value curve, the rod position is converted into reactivity. , build - The relationship, based on reactor neutron dynamics theory, is linear at an appropriate subcriticality. This linear relationship is fitted and extrapolated to... =0, thus obtaining (Here, the subscript B indicates the linear theoretical fit of the control bar corresponding to path B.) ).

[0034] S203: Perform consistency verification and final determination of the fitting results. Compare multiple results obtained from different paths (A, B) and different symmetric bars (1, 2). Estimated value ( , , These values ​​originate from the same physical essence ( However, because the measurement and fitting paths are independent, they form a cross-validation network for the "fitting process" and the "final result." If these predicted values ​​are statistically highly consistent (e.g., the standard deviation is less than a preset threshold, such as ±1.5 s), then... -1 This strongly verifies the correctness and robustness of the entire measurement and fitting process. Ultimately... The average or optimal estimate of these values ​​can be taken. If a certain estimate deviates significantly, its corresponding fitting path or individual data point can be traced, analyzed, and removed to ensure that the final result is not affected by abnormal paths.

[0035] Step 3 (Optional Extension): Systematic Verification of Multiple Sets of Symmetric Bars To obtain a higher level of verification, multiple different sets of symmetric bars can be selected within the same core load, and steps one and two can be performed in parallel. Finally, the results of all independent verification sets are synthesized to provide a more universal and statistically significant result. The final value and its uncertainty.

[0036] Example: Loading two different reactor cores on a light water critical device. For example, verification and validation: Implementation process: For each load, select a set of symmetrical control bars (e.g., select group H for load 1, group K for load 2, and group G for load 3).

[0037] Step 1: Independently measure the individual bars of each bar group. Sequence. Plot curves and compare them to confirm that the grouped curves highly overlap in most areas (see...). Figures 2-4 The data was deemed self-consistent and reliable. A slight deviation was found in the bottom region, leading to a unanimous decision to exclude that region.

[0038] Step 2: S201: Select 8 bar positions starting from the top of the bar where the two curves overlap well as the common optimization interval. S202: Observe the commonalities presented by the curves in this interval. Path A can be selected using exponential fitting, polynomial fitting, LF linear fitting, etc., to obtain... =205.98 s -1 , =206.78 s -1 Path B uses - Linear fitting yields =205.10 s -1 S203: The three values ​​are highly consistent (standard deviation is much less than ±1.15 s). -1 The verification passed. The average value is taken to obtain the load value. The final value is 205.95 s. -1 .

[0039] Step 3: In the other two loading processes, the same procedure was performed on the K group and G group of symmetric bars respectively, and the internal verification results were highly consistent.

[0040] Performance verification: Compared with the traditional method of using only a single bar (such as H1) to try multiple fittings on the full data (the result dispersion range may exceed 10 s) -1Compared to other methods, this invention uses a symmetrical bar-grouping strategy to verify data reliability, optimize and validate the fitting process, and ultimately output... The values ​​are highly accurate and reliable, perfectly achieving the purpose of verification.

[0041] A method for verifying and validating a symmetric control rod group optimization fitting strategy for reactor dynamic parameters includes: selecting a symmetric control rod group and performing independent... Sequence measurement; data self-consistency verification is completed by comparing the measurement curves of symmetrical bars; based on the verified data, the optimal fitting interval is collaboratively determined; within the optimal interval, at least two different extrapolation paths are used for fitting to obtain multiple... Estimates; the final estimate is determined by analyzing the consistency of multiple estimates. Values. Data self-consistency verification includes calculating the deviation between symmetrical bar curves; collaboratively determining the optimal fitting interval includes excluding regions where symmetrical bar curves exhibit common abnormalities; two different extrapolation paths include... - Function fitting and - Linear fitting; it also includes selecting multiple sets of symmetrical rods for systematic verification.

Claims

1. A method for verifying and validating a symmetric rod assembly optimization fitting strategy for reactor dynamic parameters, characterized in that: Step one: based on the core symmetry of data reliability check measurement, a set of original data can be obtained: S101: after the reactor establishes criticality and flattens the flux, select a pair of control rods H1 and H2 with geometric symmetry in the core, defined as the symmetric checking rod group; S102: independently and completely measure the position sequence of each rod in the symmetric rod group, that is, fix all other rods, change the position of one symmetric rod alone and measure its - value; S103: perform data self-consistency cross-checking, compare the position curves of the two symmetric rods measured - - ​ Step 2: Optimization and verification of the fitting process based on symmetric data. Using verified reliable data, implement a fitting strategy that reduces subjective sensitivity and is self-verifiable: S201: Collaborative optimization of fitting interval selection. Based on the two curves verified in Step 1, comprehensively analyze their morphological consistency, eliminate regions where both curves exhibit obvious nonlinearity, jumps, or deviations, and select a data interval where both curves perform well and are consistent as the common fitting interval; S202: Implement multi-path complementary fitting verification; S203: Perform consistency verification and final determination of fitting results.

2. The method of claim 1, wherein the method further comprises: determining a plurality of reactor dynamic parameter symmetry group rod optimization fitting strategies; and determining a plurality of reactor dynamic parameter symmetry group rod optimization fitting strategy parameters. S103: According to the principle of core physical symmetry, the two curves should ideally coincide completely. In actual operation, the overall reliability of the measurement activity is checked by calculating the deviation of the two curves at the corresponding rod positions or the overall coincidence.

3. The method of claim 2, wherein the method further comprises: determining a plurality of dynamic parameters of the reactor core; and determining a plurality of symmetric groups of rods for the reactor core based on the plurality of dynamic parameters. If the deviation exceeds the reasonable range of the engineering, it indicates that there is an abnormality in the measurement system or the core condition, and the data is unreliable. The cause must be investigated and the measurement must be repeated. If the deviation is within the preset tolerance, the measurement data is determined to be valid and reliable, and the next step of analysis can be carried out.

4. The method for verifying and validating the symmetric rod assembly optimization fitting strategy for reactor dynamic parameters according to claim 1, characterized in that: S202: Within the selected optimization interval, at least two extrapolation paths with different principles are used for fitting: Path A is direct curve fitting; ... - The rod-position relationship is fitted using a direct function, and path B linear theory fitting is used: the rod position is converted into reactivity using the control rod value curve. , build - The relationship, based on reactor neutron dynamics theory, is linear at an appropriate subcritical degree. This linear relationship is fitted and extrapolated to... =0, thus obtaining subscript B Representation and path B Linear theoretical fitting of reactor dynamic characteristic parameters corresponding to control rods S203: Compare multiple results obtained from different paths A and B and different symmetrical rods 1 and 2. Forecast , , These values ​​originate from the same physical essence. However, because the measurement and fitting paths are independent, they form a cross-validation network for the fitting process and the final result.

5. The method for verifying and validating the symmetric rod assembly optimization fitting strategy for reactor dynamic parameters according to claim 1, characterized in that: The deviated areas include the boundary effect zone when the rod is positioned too deep.

6. The method for verifying and validating the symmetric rod assembly optimization fitting strategy for reactor dynamic parameters according to claim 4, characterized in that: The type of fitting function is not fixed in advance, but is adaptively selected based on the common morphological characteristics exhibited by the two symmetrical curves within the optimization interval.

7. The method for verifying and validating the symmetric rod assembly optimization fitting strategy for reactor dynamic parameters according to claim 6, characterized in that: If both curves exhibit an exponential decay trend within this interval, then an exponential fitting method is uniformly used. This method is applied to the independent data of both bars and extrapolated to obtain the desired results. and subscript A1 and A2 This represents the direct curve fitting of the two symmetrical bars corresponding to path A. .

8. The method for verifying and validating the symmetric rod assembly optimization fitting strategy for reactor dynamic parameters according to claim 4, characterized in that: If these estimates are highly consistent statistically, it strongly validates the correctness and robustness of the entire measurement and fitting process, ultimately... Take the average or optimal estimate of these values; if a certain estimate deviates significantly, trace its corresponding fitting path or individual data point, analyze and remove it to ensure that the final result is not affected by abnormal paths.

9. The method for verifying and validating the symmetric rod assembly optimization fitting strategy for reactor dynamic parameters according to claim 8, characterized in that: Highly consistent is a standard deviation less than a preset threshold of 1.5 s -1 .

10. The method for verifying and validating the symmetric rod assembly optimization fitting strategy for reactor dynamic parameters according to claim 1, characterized in that: The process also includes step three: systematic verification of multiple sets of symmetric bars. Multiple different sets of symmetric bars are selected within the same core load, and steps one and two are executed in parallel. Finally, the results of all independent verification sets are synthesized to provide a more universal and statistically significant assessment. The final value and its uncertainty.

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