Method for determining change in fission rate after critical accident

Abstract

The embodiment of the invention relates to the field of electric digital data processing, in particular to a method for determining the change of the fission rate after a critical accident. According to the method for determining the change of the fission rate after the critical accident provided by the embodiment of the invention, the database is constructed for the source item information of the existing critical accident data; reactivity introduction and fission rate data after an accident can be predicted according to collected dose data of a current critical accident and existing source item information in a database, and then an image of the fission rate changing along with time is generated. In this way, the change condition of the source item of the fission power after the critical accident can be visually and rapidly obtained, the exposure dose of related personnel can be conveniently estimated, then targeted classified treatment can be rapidly carried out, accurate intervention can be implemented at the moment when the accident develops to low power, and the treatment efficiency is improved. The accident process is ended in advance under the condition of reducing the exposure dose of the intervening personnel as much as possible, and the harm caused by the accident is further reduced.

Description

Technical Field

[0001] Embodiments of this application relate to the field of electronic digital data processing, and in particular to a method for determining the change in fission rate after a critical accident. Background Technology

[0002] The statements herein are provided merely as background information in connection with this application and do not necessarily constitute prior art.

[0003] Solution-based nuclear material systems, due to the presence of water or other moderators, have low criticality masses, are difficult to control, and pose a significant risk of nuclear criticality. Typically, nuclear criticality alarm systems are installed in nuclear material production and reprocessing facilities with high criticality risks. These systems utilize monitoring and alarm technologies to detect criticality accidents, enabling immediate alerts in their early stages and prompting emergency evacuation of personnel. This significantly reduces radiation exposure and the consequences of accidents. Summary of the Invention

[0004] A brief overview of this application is provided below to offer a basic understanding of certain aspects thereof. It should be understood that this overview is not an exhaustive summary of the application. It is not intended to identify key or essential parts of the application, nor is it intended to limit its scope. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0005] An embodiment of this application provides a method for determining the change in fission rate after a critical accident, comprising the following steps: S10: determining source term information based on existing critical accidents; S20: constructing a critical accident response database based on the source term information; S30: determining the dose data of the current critical accident; S40: determining the estimated reactivity introduction magnitude of the critical accident based on the critical accident response database and the dose data; S50: determining the predicted value of the fission rate after the critical accident based on the critical accident response database and the estimated reactivity introduction magnitude; S60: determining the fission rate change over time under the current reactivity introduction based on the predicted value of the fission rate after the critical accident.

[0006] The method for determining the change in fission rate after a critical accident provided in the embodiments of this application constructs a database based on source term information of existing critical accident data. This allows for the prediction of reactive input and fission rate data after a critical accident occurs, based on collected dose data of the current critical accident and existing source term information in the database, thereby generating a graph of fission rate changes over time. This provides a direct and rapid understanding of the changes in source terms of fission power after a critical accident, facilitating the estimation of radiation dose to relevant personnel. This enables rapid and targeted treatment and allows for precise intervention when the accident progresses to a lower power level, terminating the accident process earlier while minimizing radiation dose to those involved, thus further reducing the harm caused by the accident. Attached Figure Description

[0007] To further illustrate the above and other advantages and features of this application, the specific embodiments of this application will be described in more detail below with reference to the accompanying drawings. The drawings, together with the following detailed description, are included in and form a part of this specification. Elements having the same function and structure are indicated by the same reference numerals. It should be understood that these drawings only depict typical examples of this application and should not be considered as limiting the scope of this application.

[0008] Figure 1 This is a flowchart illustrating a method for determining the change in fission rate after a critical accident, as provided in an embodiment of this application. Detailed Implementation

[0009] Exemplary embodiments of this application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this application.

[0010] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the equipment structure and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0011] The following disclosure provides several different implementations or examples for carrying out this application. To simplify the disclosure of this application, specific examples of components and methods are described below. Of course, these are merely examples and are not intended to limit this application. In the description of the embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0012] Currently, the criticality accident alarm systems installed in nuclear material production and reprocessing facilities with high criticality risks only provide alarm information after the first fission peak appears, based on the detected extremely high neutron or gamma dose signals. They lack criticality accident inversion and prediction capabilities, making it impossible to achieve a more refined evaluation of the consequences of criticality accidents and thus unable to provide support for the handling and disposal of accident consequences. There is currently no method that can predict the subsequent process of criticality accidents by inverting accident data.

[0013] Embodiments of this application provide a method for determining the change in fission rate after a critical accident. Figure 1 This application provides a schematic flowchart illustrating a method for determining the change in fission rate after a critical accident, as illustrated in an embodiment of the present application. Figure 1 As shown, it includes the following steps: S10: Determine source term information based on existing critical accidents; S20: Construct a critical accident response database based on the source term information; S30: Determine the dose data of the current critical accident; S40: Determine the estimated reactivity introduction size of the critical accident based on the critical accident response database and the dose data; S50: Determine the predicted value of the fission rate after the critical accident based on the critical accident response database and the estimated reactivity introduction size; S60: Determine the fission rate change over time under the current reactivity introduction based on the predicted value of the fission rate after the critical accident.

[0014] The method for determining the change in fission rate after a critical accident provided in the embodiments of this application constructs a database based on the source term information of existing critical accident data. This allows for the prediction of reactive input and fission rate data after a critical accident occurs, based on the collected dose data of the current critical accident and existing data in the database, thereby generating a graph of fission rate changes over time. This provides a direct and rapid understanding of the changes in the source terms of fission power after a critical accident, facilitating the estimation of radiation dose to relevant personnel. This enables rapid and targeted treatment and allows for precise intervention when the accident progresses to a lower power level, terminating the accident process earlier while minimizing radiation dose to those involved, thus further reducing the harm caused by the accident.

[0015] In some embodiments, step S40 further includes the following steps: S41: determining the characteristic value of the dose data based on the dose data; S42: determining the corresponding characteristic data in the critical accident response database based on the characteristic value of the dose data; S43: determining the magnitude of the critical accident predicted reactivity introduction based on the corresponding characteristic data.

[0016] In some embodiments, after a critical accident occurs, an alarm is triggered and dose data is continuously output (e.g., a current neutron dose rate is output every 1 ms; a dose rate change file is output every 100 ms). This allows for the immediate acquisition of the dynamic distribution of radiation dose within the nuclear material system after a critical accident. Since the magnitude of reactivity introduction determines the dose rate level, the current magnitude of reactivity introduction can be determined based on the existing output dose data, thereby determining the estimated magnitude of reactivity introduction.

[0017] In some embodiments, in step S41, the dose data includes peak dose rate and trough dose rate, and the peak dose rate, trough dose rate, and characteristic values ​​of the dose data satisfy the following relationship: characteristic value of dose data = peak dose rate / trough dose rate. The peak dose rate and trough dose rate should be temporally adjacent, so that the characteristic values ​​of the dose rate can intuitively reflect the current dose rate change.

[0018] Since the characteristic value of dose data is the ratio of the peak dose rate to the trough dose rate, i.e., the characteristic value of dose data is a relative value, determining the characteristic value of dose data in the above way can cancel out the effects of spatial shielding, scattering and other factors, thereby avoiding complex calculation corrections and experimental calibration.

[0019] In some embodiments, in step S10, the source term information includes the change of the critical accident fission rate over time within a predetermined reactivity introduction range, fission rate data within a predetermined time period, and characteristic values ​​of the fission rate data. This fission rate-related source term information can comprehensively reflect the changes in fission rate data after the occurrence of a critical accident, which is beneficial for predicting subsequent changes in the fission rate based on the aforementioned source term information in the critical accident response database after the occurrence of a critical accident, thereby predicting the development process of the nuclear material system after a critical accident, and thus helping to make decisions on emergency measures after a critical accident.

[0020] In some embodiments, the predetermined reactivity introduction range can be set to 1 to 12 ($, where $ represents the size of the reactivity introduction), the predetermined time can be set to within 120 seconds, and the fission rate data can include the number of fission peaks, the time of occurrence of fission peaks, the size of fission peaks, and the characteristic values ​​of the fission data corresponding to all fission peaks.

[0021] In some embodiments, the critical accident response database should also contain minimum reactivity introduction data corresponding to 1 to 17 fission peaks, so as to fully reflect the contribution of fission peaks to global reactivity and thus accurately predict real critical accident scenarios.

[0022] In some embodiments, during the calculation of the change of critical accident power or fission rate over time under different reactivity conditions, a maximum time step of 10 is selected. -4 The shortest calculation time is 120 seconds.

[0023] In some embodiments, in step S43, the corresponding feature data is set as fission rate data, and the feature values ​​of the fission rate data are interpolated based on the feature values ​​of the dose data to determine the magnitude of the critical accident prediction reactivity introduction.

[0024] Since the fission rate directly reflects the fission power level, and the fission power is directly determined by the introduction of reactivity, by interpolating the fission rate data in the critical accident response database, it is possible to determine accident data similar to the current accident from the critical accident response database, thereby enabling the prediction of future reactivity introduction based on existing accident data, making the prediction more scientific and accurate.

[0025] In some embodiments, the interpolation methods for eigenvalues ​​include, but are not limited to, linear interpolation, cubic spline interpolation, etc.

[0026] In some embodiments, fission rate data includes a peak fission rate and a trough fission rate. The peak fission rate, the trough fission rate, and the eigenvalues ​​of the fission rate data satisfy the following relationship: eigenvalue of fission data = peak fission rate / trough fission rate. Since the eigenvalues ​​of fission data are the ratio of the peak fission rate to the trough fission rate, i.e., the eigenvalues ​​of fission data are relative values, determining the eigenvalues ​​of dose data in the above manner can offset the effects of spatial shielding, scattering, and other factors, thereby avoiding complex calculation corrections and experimental calibrations.

[0027] Specifically, the fission rate 50ms after the fission peak can be defined as the fission rate valley. The ratio of the fission rate peak and the fission rate valley that are adjacent in time can be used as the feature value of the fission rate data corresponding to the current reactive introduction. This allows the feature value of the fission rate to intuitively reflect the characteristics of the current reactive introduction and improves the computational efficiency.

[0028] Because of the high propagation speed of neutrons and the rapid response speed of detectors, it can be assumed that the dose rate change detected after a nuclear criticality accident is synchronous with the fission rate change data of the criticality accident. Therefore, the magnitude of the predicted reactivity introduction of the criticality accident can be determined based on the characteristic values ​​of the dose data and the fission rate data.

[0029] In some embodiments, step S50 further includes the following steps: S51: determining reactive data adjacent to the estimated reactive introduction size in the critical accident response database based on the estimated reactive introduction size; S52: determining a predicted fission rate based on the adjacent reactive data, wherein the predicted fission rate includes the number of fission peaks, the fission peak time, and the fission peak size. Determining the predicted fission rate based on adjacent reactive data in the database allows for the identification of accident data similar to the current accident from the critical accident response database, thereby enabling the prediction of future fission data based on existing accident data, making the predicted fission rate more scientific and accurate.

[0030] In some embodiments, in step S52, the number of fission peaks is determined based on the smaller value among adjacent reactivity data.

[0031] In some embodiments, since there is a strong linear relationship between the fission peak size and reactivity under different reactivity introductions, the fission peak size can be determined by linear interpolation of adjacent reactivity data in step S52.

[0032] In some embodiments, since the correlation between the fission peak time and the reactivity introduction is relatively poor, in step S52, the fission peak time can be determined by means of logarithmic or cubic spline interpolation of adjacent reactivity data.

[0033] In some embodiments, step S60 further includes the following steps: S61: determining a graph of the fission rate changing over time under the current reactivity introduction based on the smaller value among adjacent reactivity data; S62: correcting the graph of the fission rate changing over time under the current reactivity introduction based on the predicted value of the fission rate. Based on the graph of the fission rate changing over time under the current reactivity introduction, the trajectory of an accident can be intuitively obtained within a short period after the accident occurs, enabling the inversion and prediction of the accident process.

[0034] In some embodiments, in step S61, the image of the fission rate over time under the current reactivity is corrected based on the image of the fission rate over time under the adjacent smaller reactivity.

[0035] In some embodiments, step S62 further includes the following steps: S621: determining the shape of the main fission peak in the image based on the fission peak size; S622: determining the time of the main fission peak in the image based on the fission peak time; S623: determining the overall decreasing fission rate curve after the fission peak based on the fission rate value at a predetermined time.

[0036] In some embodiments, in step S621, the shape of the main fission peak can be scaled as a whole based on the interpolation result of the fission peak.

[0037] In some embodiments, in step S622, the main fission peak time can be shifted on the time axis based on the interpolation result of the fission peak time.

[0038] In some embodiments, in step S623, the fission rate curve that decreases as a whole after the fission peak can be linearly interpolated and corrected based on the fission rate value at time 120s.

[0039] In some embodiments, in step S10, the corresponding source term information of existing critical accidents can be determined based on the considered potential critical safety risk points.

[0040] Regarding the embodiments of this application, it should also be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other to obtain new embodiments.

[0041] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. The scope of protection of this application shall be determined by the scope of the claims.

Claims

1. A method of determining a change in post-accident fission rate, characterized by, It comprises the following steps: S10: determining source item information according to existing critical accidents; S20: constructing a critical accident response database according to the source item information; S30: determining dose data of a current critical accident; S40: determining a critical accident estimated reactivity insertion size according to the critical accident response database and the dose data; S50: determining a predicted value of a post-critical accident fission rate according to the critical accident response database and the estimated reactivity insertion size; S60: determining a time-varying image of the fission rate under a current reactivity insertion according to the predicted value of the post-critical accident fission rate.

2. The method of claim 1, wherein, In the step S40, it further comprises the following steps: S41: determining a characteristic value of the dose data according to the dose data; S42: determining corresponding characteristic data in the critical accident response database according to the characteristic value of the dose data; S43: determining the critical accident estimated reactivity insertion size according to the corresponding characteristic data.

3. The method of claim 2, wherein, In the step S10, the source item information comprises a time-varying change of a critical accident fission rate under a predetermined reactivity insertion range, fission rate data within a predetermined time, and a characteristic value of the fission rate data.

4. The method of claim 3, wherein, In the step S43, the corresponding characteristic data is set as the fission rate data, and an interpolation is performed on the characteristic value of the fission rate data according to the characteristic value of the dose data to determine the critical accident estimated reactivity insertion size.

5. The method of claim 2, wherein, In the step S41, the dose data comprises a dose rate peak value and a dose rate valley value, and the dose rate peak value, the dose rate valley value, and the characteristic value of the dose data satisfy the following relationship: Characteristic value of dose data = dose rate peak value / dose rate valley value.

6. The method of claim 4, wherein, The fission rate data comprises a fission rate peak value and a fission rate valley value, and the fission rate peak value, the fission rate valley value, and the characteristic value of the fission rate data satisfy the following relationship: Characteristic value of fission data = fission rate peak value / fission rate valley value.

7. The method of claim 1, wherein, In the step S50, it further comprises the following steps: S51: determining reactivity data adjacent to the estimated reactivity insertion size in the critical accident response database according to the estimated reactivity insertion size; S52: determining the predicted value of the fission rate according to the adjacent reactivity data, and the predicted value of the fission rate comprises a number of upcoming fission peaks, a fission peak time, and a fission peak value size.

8. The method of claim 7, wherein, In the step S52, the number of fission peaks is determined according to a smaller value in the adjacent reactivity data.

9. The method of claim 7, wherein, In the step S60, it further comprises the following steps: S61: determining a time-varying image of the fission rate under the current reactivity insertion according to the smaller value in the adjacent reactivity data; S62: correcting the time-varying image of the fission rate under the current reactivity insertion according to the predicted value of the fission rate.

10. The method of claim 9, wherein, In the step S62, it further comprises the following steps: S621: determining a shape of a main fission peak in the image according to the fission peak value size; S622: determining a main fission peak time in the image according to the fission peak time. S623: Determine the overall post-fission-peak fission rate curve from the fission rate values at the predetermined times. S623: Determine the overall post-fission-peak fission rate curve from the fission rate values at the predetermined times.

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