Method and system for calculating fission stock and impurity activity release amount of reactor core

Abstract

The invention relates to a method and a system for calculating fission stock and impurity activity release amount of a reactor core. The method comprises the following steps: constructing a model of the reactor core and a fuel element; controlling the fuel element model to circularly flow in the reactor core model, and dividing the whole process time of the circular flow into a plurality of time steps; the fission stock and the impurity activity release amount of each fuel element model in each time step are calculated, and calculation results are obtained; when the refueling batch is one time and an effective multiplication factor is calculated through a reactor core physical calculation program and meets a set threshold value, a calculation result is stored in a first array; when the number of the refueling batches is at least two and the fuel element model burnup and the unloading burnup meet the preset conditions, the calculation result of the circular flow is stored in a second array; and obtaining calculation results of the fission stock and the impurity activity release amount of the reactor core through the first array or the second array. The problems that the accumulation amount and the impurity activation rate of fission products cannot be accurately calculated, and the historical track of the fuel element is difficult to track are solved.

Description

Technical Field

[0001] This disclosure relates to the field of reactor technology, and in particular to a method and system for calculating core fission stock and impurity activity release. Background Technology

[0002] The design concept of the pebble bed high-temperature gas-cooled reactor (PTC) is centered on inherent safety and efficient energy conversion, achieving continuous operation through a core composed of millions of TRISO particles and hundreds of thousands of fuel elements. During operation, the calculation of fission product stock and the assessment of impurity activation and release are directly related to the control of primary loop radioactive source terms, optimization of equipment maintenance dosage, and long-term environmental compliance, forming a key technological foundation supporting its commercial operation.

[0003] The fuel elements flow continuously within the reactor core, experiencing different power histories; each fuel element itself is a small, multi-layered defense system: fission occurs in the TRISO particle core, the outer silicon carbide layer is used to block the release of radioactive nuclides; the graphite matrix provides structural support and moderation, but the trace manufacturing impurities (such as boron and cobalt) remaining in it are activated and fissioned in a high-energy neutron environment, far exceeding the complexity of traditional stationary fuel rod reactors.

[0004] Because the fuel elements move under the drive of helium and mix randomly after entering the reactor core, the static burnup distribution model of traditional pressurized water reactors cannot accurately calculate the accumulation of fission products and the activation rate of impurities, making it difficult to track the historical trajectory of the fuel elements. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides a method for calculating the core fission stock and impurity activity release. The method includes the following steps: The reactor core model and multiple fuel element models were constructed using the target pebble bed reactor parameters and fuel element parameters, respectively. According to the fuel management parameters, multiple fuel element models are filled into the core model according to the loading amount, and each fuel element model is uniquely identified. The fuel management parameters include: refueling batch, fuel element loading amount, and unloading burnup. The fuel element model is controlled to circulate in the reactor core model, and the entire process of the circulation is divided into multiple time steps; The fission stock and impurity activity release of each fuel element model within each time step are calculated using a unique identifier to obtain the calculation results; When the material replacement batch is once and the calculated effective growth factor meets the set threshold, the calculation result is stored in the first array; When the refueling batch is at least twice and the fuel element model fuel consumption is greater than or equal to the unloading fuel consumption, the calculation results of each cycle flow are stored in the second array; The calculated results of the core fission stock and the impurity activity release are obtained by summing the fission stock and the impurity activity release of the first array or the second array.

[0006] Furthermore, the calculation of the fission stock and impurity activity release of each fuel element model within each time step using a unique identifier, to obtain the calculation results, includes: The fission rate of the core material of the fuel element model, the fission rate of the free uranium content, the impurity activation release rate, and the total radioactivity generation rate are calculated using the unique identifier for each time step.

[0007] Furthermore, when the material replacement batch is once and the calculated effective growth factor meets a set threshold, storing the calculation result in a first array includes: When the refueling batch is a single pass, the reactor's neutron balance is calculated based on the fission parameters of the fuel element model; The effective multiplication factor of the reactor core model is obtained based on the neutron budget balance calculation. When the core reaches equilibrium based on the effective multiplication factor and the set threshold, the calculation result is output and stored in the first array.

[0008] Furthermore, the step of determining whether the reactor core has reached equilibrium based on the effective multiplication factor and a set threshold includes: When the difference between the effective multiplication factor in two consecutive time steps is less than or equal to a set threshold, the reactor core is determined to be in a balanced state.

[0009] Furthermore, when the refueling batch is at least twice and the fuel element model fuel consumption is greater than or equal to the unloading fuel consumption, the calculation results of each cycle flow are stored in a second array, including: Step A: Store the calculation results of the initial loop flow in the second array; Step B: Input the new enriched fuel element model into the core model after unloading the fuel element model; Step C: Obtain the fuel element model burnup and the unloading burnup parameters after at least two refueling cycles of the reactor core model; Step D: Determine the difference between the fuel element model burnup and the unloading burnup. When the difference is negative, the fuel element model continues to cycle in the core model. When the difference is positive, unload each fuel element model and store the calculation result in the second array. Repeat steps B to D until the set refueling batch is met.

[0010] Furthermore, step B includes: The unique identifier of the discharged fuel element model is assigned to the newly enriched fuel element model.

[0011] Furthermore, the step of obtaining the core fission stock and impurity activity release by summing the fission stock and impurity activity release amounts in the first array or the second array includes: The fission stock and impurity activity release of all fuel element models in the first array are summed to obtain the calculated core model fission stock and impurity activity release. Alternatively, the fission stock and impurity activity release of all fuel element models in the second array can be summed to obtain the calculated fission stock and impurity activity release of the core model.

[0012] This application also provides a system for calculating core fission stock and impurity activity release, characterized in that it includes: The module is used to obtain the parameters of the target pebble bed reactor and the fuel element parameters to construct models of the reactor core and fuel elements respectively; The filling module is used to fill the fuel element model into the core model according to the loading amount based on the pre-acquired fuel management parameters and to uniquely identify each fuel element model. The fuel management parameters include: refueling batch, fuel element loading amount and unloading burnup. The partitioning module is used to control the fuel element model to circulate in the core model through the core physics calculation program, and to divide the entire process of the circulation flow into multiple time steps; The calculation module is used to calculate the fission stock and impurity activity release of each fuel element model within each time step using the unique identifier, and obtain the calculation results; The first storage module is used to store the calculation result in a first array when the refueling batch is once and the effective multiplication factor is calculated by the core physics calculation program and meets the set threshold. The second storage module is used to store the calculation results of each cycle flow in a second array when the refueling batch is at least twice and the fuel element model fuel consumption and the unloading fuel consumption meet preset conditions; The accumulation module is used to obtain the calculation results of the core fission stock and the impurity activity release by accumulating the fission stock and the impurity activity release of the first array or the second array.

[0013] This application also provides a computer device, including a memory and a processor, wherein the memory stores computer-readable instructions, and the processor executes the computer-readable instructions to perform the steps of calculating the core fission stock and impurity activity release.

[0014] This application also provides a computer-readable storage medium storing computer-readable instructions, which, when executed by a processor, implement the steps of calculating the core fission stock and impurity activity release.

[0015] The technical solution provided in this disclosure has the following advantages compared with the prior art: This application overcomes the shortcomings of traditional static burnup distribution models in pebble bed high-temperature gas-cooled reactors (HTGRs) under conditions of random fuel flow and power history differences. It involves constructing a core geometric model and fuel element models, uniquely identifying each fuel element, and calculating fission yield and impurity activation release sphere-by-sphere using a core physics calculation program at the main / sub-time step. The calculation results are organized and accumulated according to a single-pass or multi-pass fuel management strategy. This method can be used for fuel management optimization, maintenance dosage control, regulatory compliance, and long-term environmental assessment, and facilitates online decision-making, sensitivity analysis, and process optimization, thereby improving the safety, economy, and auditability of core operation. It achieves high-precision, traceable, and time-sequential calculation of core fission reserves and impurity activity release. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the method for calculating the core fission stock and impurity activity release amount as described in the embodiments of this disclosure. Figure 2 This is a flowchart of a method for changing materials in one batch, as described in an embodiment of this disclosure. Figure 3 This is a flowchart of the calculation system for core fission stock and impurity activity release as described in the embodiments of this disclosure. Detailed Implementation

[0019] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0020] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0021] Figure 1 This is a flowchart illustrating the method for calculating core fission stock and impurity activity release as described in this embodiment. The method includes: Step S101: Construct the core model and multiple fuel element models using the target pebble bed reactor parameters and fuel element parameters, respectively; In this embodiment, the pebble bed reactor parameters include: core diameter, height, and the angle of its bottom funnel region; the thickness of the reflector (graphite reactor internals); the geometric parameters of the number, distribution location, and diameter of the cold helium channels, the first shutdown system, and the second shutdown system; and the volume fraction of the fuel elements loaded in the core is 0.61. The fuel element parameters include: the geometric and material parameters of the overall diameter of the fuel elements loaded in the core and the diameter of the fuel-free zone; the geometric and material parameters of the coating layer thickness of the dispersed coating particles inside the fuel element and the core diameter; the free uranium content and impurity element j and its content (j=1, ..., M, where M is the content of the impurity element); and the volume fraction VF of the dispersed TRISO particles inside the fuel element. A core geometric calculation model is established using a neutron physics calculation program. Based on the target pebble bed reactor parameters and fuel element parameters, geometric models of the core and its lower funnel region, the reflector and various channels, the first shutdown system, and the second shutdown system are established sequentially. The engineering parameters are formalized into geometric and material models that can be used for numerical calculations. This ensures that subsequent neutron physics calculations have complete and consistent geometric and material inputs, eliminating sources of calculation error caused by parameter ambiguity. It improves the physical realism of the simulation and the consistency of boundary conditions, thereby enhancing the reliability and engineering usability of the calculation results (e.g., shielding / cooling design, accurate capture of the influence of pore distribution on flux fields).

[0022] Specifically, a dispersed TRISO particle model is constructed using geometric models of the reactor core and fuel elements, with the dispersed quantity satisfying the volume fraction (VF). Based on the geometric models of the reactor core, fuel elements, and dispersed TRISO particles, the atomic density of each nuclide is calculated. At the fuel element scale, the TRISO particle geometry, coating layer, and volume fraction are converted into numerical parameters such as the atomic density of each nuclide, which can be inserted into the fission and activation formulas. This connects macroscopic geometry with microscopic nuclear data, providing a clear physical basis for the calculation of fission rate and activation rate. It reduces nuclide concentration estimation errors, making the calculation of fission stock and activation release more accurate; it supports sensitivity analysis and optimization for different fuel processes (different TRISO specifications or VFs); and it provides a basis for formulas (…). , , , Provide full implementation support for its use.

[0023] Step S102: According to the fuel management parameters, multiple fuel element models are filled into the core model according to the loading amount, and each fuel element model is uniquely identified. The fuel management parameters include: refueling batch, fuel element loading amount, and unloading burnup. In this embodiment, the established fuel element model is used to fill the core area according to the fuel element loading amount, and the filling meets the volume fraction requirement (e.g., 0.61). Each fuel element is labeled, and the control flow software extracts the position coordinates and sequence number of the fuel element. Based on the fuel management parameters of the pebble bed high-temperature gas-cooled reactor core, the refueling method, fuel element type and enrichment, refueling batch X, fuel element loading amount N, and unloading burnup BU are determined. goal Based on the determined material replacement batch, if it passes in one go, the material replacement batch X=1, and the unloading fuel consumption BU. goal For any value, no setting is required; if it is "multiple passes", the material change batch X > 1, and the unloading fuel consumption BU goal The system designs fuel element burnup values; it numbers each physical model and inputs its spatial location information into the data system, forming a searchable fuel element database. Each fuel element becomes a traceable minimum calculation unit (with metadata such as number, initial parameters, and loading time). It enables sphere-by-sphere tracking and historical recording (power history, burnup history, location changes); providing verifiable data sources for unloading determination, decommissioning, and radioactive disposal.

[0024] Step S103: Control the fuel element model to circulate in the core model, and divide the entire circulation process into multiple time steps; In this embodiment, the flow and fuel consumption processes are discretized and simulated using a time-domain subdivision method, with physical quantities accumulated over multiple time steps to approximate a continuous process. This supports accurate descriptions of transient, transitional, and long-term equilibrium states, providing necessary time-series information for safety analysis.

[0025] Step S104: Calculate the fission stock and impurity activity release of each fuel element model within each time step using the unique identifier, and obtain the calculation results; In this embodiment, the control flow software calls the core physics program to define the fuel element type and enrichment, and sets the cycle mode constraints of the fuel elements in the core according to the refueling batch; the control flow software calls the core physics program to initialize the model calculation; obtains high-resolution data of the evolution of each fuel element over time (instantaneous / cumulative fission yield, activation release rate, etc.); and can capture position dependence and time dependence (e.g., the difference in flux caused by passing through different core locations, resulting in burnup differences).

[0026] Figure 2 The following is a flowchart of the method for changing materials once according to an embodiment of this disclosure; Step S105: When the material changing batch is once and the calculated effective proliferation factor meets the set threshold, the calculation result is stored in the first array; In this embodiment, the effective multiplication factor (keff) is a key parameter describing the sustainability of the chain reaction in nuclear fission in a nuclear reactor. Under a one-pass refueling strategy, when the core physics calculation program determines that the effective multiplication factor has converged to a set threshold (e.g., Δkeff ≤ 5 ppm before and after the calculation time step), the fission stock and impurity activity release of each fuel element in each sub-time step (time step) are written into a first array, forming a complete lifecycle source term record. Data is archived only after the core reaches equilibrium, ensuring that the stored data represents the true source term distribution of periodically stable operation. This generates a stable and complete fission and activation history (instantaneous and cumulative values ​​for the entire one-pass process). This provides verifiable baseline data for post-operation analysis, improving decision-making credibility.

[0027] Step S106: When there are at least two refueling batches and the fuel element model fuel consumption is greater than or equal to the unloading fuel consumption, store the calculation results of each cycle flow in the second array. In this embodiment, under the multiple refueling strategies, when the fuel consumption of a single sphere reaches or exceeds the design unloading fuel consumption (BU≥BU), goal When the preset criteria are met, the fission stock and impurity activity release of the sphere at each time step are written into the second array, which can accurately track the cumulative burnup effect and cyclic contribution. BU goal As a trigger condition, the cumulative and time-series data of the pebble bed stack are archived only when the stack reaches the designed unloading burnup, maintaining consistency between archiving and unloading decisions. Historical records are generated by cycle number and unloading time, reflecting the actual contribution of accumulated burnup to fission yield and impurity activation.

[0028] Step S107: By summing the fission stock and impurity activity release of the first array or the second array, the calculation results of the core fission stock and impurity activity release are obtained.

[0029] In this embodiment, based on the refueling batch setting mode, data is stored in either a first data set or a second array, and the values ​​are accumulated and summarized to form macroscopic indicators (time series and cumulative values) for the entire reactor core. This generates usable core-level outputs, including whole-core fission yield curves, activity release curves for various impurities, extra-core release estimates, and accumulated radioactive stockpiles. This provides quantitative basis for engineering design and supports fuel management decisions (such as optimizing refueling batch X, adjusting unloading fuel BUs).goal (and economic / security trade-offs)

[0030] In some optional embodiments, step S104 calculates the fission stock and impurity activity release of each fuel element model within each time step using a unique identifier, and obtains the calculation results, including: The fission rate of the core material of the fuel element model, the fission rate of free uranium content, the impurity activation release rate, and the total radioactivity generation rate are calculated for each time step using a unique identifier. The fission rate formula for the core material of the fuel element model is as follows: ; In the formula: The fission rate of the core material in the fuel element model; The atomic density of fission nuclide i; The microscopic fission cross section of the core material of the fuel element model; Neutron flux; The formula for the fission rate of free uranium is as follows: ; In the formula: The fission rate is the percentage of free uranium. The atomic density of fission nuclide i; The microscopic fission cross section represents the free uranium content; Neutron flux; The formula for the impurity activation and release rate is as follows: ; In the formula: The activation and release rate of impurities; The atomic density of impurity nuclide j; The cross section represents the microscopic activation reaction. Neutron flux; The formula for the total radioactivity production rate is as follows: ; In the formula: The total radioactivity production rate; The off-pile release rate; The fission rate of the core material in the fuel element model; The fission rate is the free uranium content. The activation and release rate of impurities.

[0031] In this embodiment, core fission, free uranium fission, and impurity activation are modeled separately, making the calculation results more consistent with real operating conditions, especially for a more accurate characterization of the complex fuel distribution in pebble bed reactor cores. This method calculates the impurity activation release rate separately, accurately assessing its contribution to the radioactive source term, which is beneficial for dose management and environmental compliance analysis. Stepwise calculations at time-step resolution can track the dynamic evolution of fuel within the reactor core, thus supporting refined source term prediction. This is particularly critical for pebble bed reactors in continuous refueling mode, as the fuel history is complex and the cumulative effect is significant. By obtaining a high-precision total radioactivity generation rate, operators can optimize core shielding and ventilation systems during the design phase; develop more scientific maintenance plans during the operation and maintenance phase; and provide a transparent and traceable data foundation for safety supervision, reducing operation and maintenance and environmental risks.

[0032] In some optional embodiments, step S105, when the refueling batch is once and the effective multiplication factor is calculated by the core physics calculation program and meets the set threshold, stores the calculation result in a first array, including: Step S1051: When the refueling batch is a single pass, calculate the reactor's neutron balance based on the fission parameters of the fuel element model. Step S1052: Obtain the effective multiplication factor of the reactor core model based on neutron budget balance calculation; Step S1053: When the core is in equilibrium, the calculation results are output and stored in the first array after determining that the effective multiplication factor and the set threshold have been reached.

[0033] In this embodiment, under the single-pass refueling mode, fuel elements undergo only one core cycle. Therefore, the effective multiplication factor (keff) can be calculated using core physics programs to reflect the overall neutron budget balance of the core. When the calculated keff matches a set threshold condition, it indicates that the core has reached a balanced operating state. In this state, the spatial coordinates, sequence number, burnup, and corresponding fission stock and impurity activity release of each fuel element model are output and stored in a first array, forming a complete core operating baseline database. By ensuring that data acquisition occurs in a balanced core state, the impact of transient disturbances on statistical results is avoided. By storing detailed fuel parameters and spatial coordinate information, not only can accurate source term tracing and safety analysis be achieved, but verifiable data support can also be provided for design optimization, thereby improving the accuracy and compliance reliability of nuclide inventory assessment under the single-pass operation mode.

[0034] In some optional embodiments, step S1053, determining whether the reactor core has reached equilibrium based on the effective multiplication factor and a set threshold, includes: When the difference in effective multiplication factor within two consecutive time steps is less than or equal to a set threshold, the reactor core is determined to be in a balanced state.

[0035] In this embodiment, when the core physics program calculates the reactor core's keff and the Δkeff ≤ 5ppm for two consecutive time steps before and after the calculation, the control flow software considers the core to have entered a balanced state and outputs a flag "1". At this time, the core physics program statistically analyzes and outputs the coordinates, serial numbers, burnup, fission rates of the corresponding fuel element model core materials, fission rates of free uranium content, impurity activation release rates, and total radioactivity generation rates of all fuel elements within the core. The control flow software stores this data in the first array Q. By setting a threshold (e.g., Δkeff ≤ ppm) and requiring that the condition be met for two consecutive time steps, a balance determination criterion is formed. This not only considers the results of a single calculation but also introduces a time stability requirement, thereby avoiding misjudgments caused by accidental numerical fluctuations. This determination method ensures that the results are output only when the core enters a truly stable physical state, thus significantly improving the reliability of the calculated data. For long-term reactor design, this mechanism reduces deviations caused by instantaneous calculation errors or statistical uncertainties, improving the accuracy of fuel management and radioactive stockpile calculations.

[0036] In some optional embodiments, step S106, when the refueling batch is at least twice and the fuel element model fuel consumption and unloading fuel consumption meet preset conditions, stores the calculation results of each cycle flow in a second array, including: Step A: Store the calculation results of the initial loop flow in the second array; Step B: Input the new enriched fuel element model into the core model after unloading the fuel element model; Step C: Obtain the fuel element model burnup and unloading burnup parameters from at least two refueling cycles of the reactor core model; Step D: Determine the difference between the fuel element model burnup and the unloading burnup. If the difference is negative, the fuel element model continues to cycle in the core model. If the difference is positive, unload each fuel element model and store the calculation results in the second array. Repeat steps B to D until the set refueling batch is met.

[0037] In this embodiment, when the refueling batch X = 1, for each discharged fuel element, the core physics program outputs the power history of the sphere, its position at the time point ti of the time step, the burnup history, and the historical information of various release rates. The control flow software stores them in the second array S, and then inserts new enrichment fuel elements into the core, assigning the serial number of the discharged fuel element to the newly inserted fuel elements with a new enrichment. When the refueling batch X ≥ 2, the core physics program determines the relationship between the burnup BU of the fuel element discharged from the core and the discharge burnup BUgoal: if BU < BUgoal, the fuel element continues to be inserted into the core for recycling; if BU ≥ BUgoal, the fuel element is "discharged". The core physics program outputs the power history of the sphere, its position at the time point ti, the burnup history, and the historical information of various release rates. The control flow software stores them in the second array S, and then inserts new enrichment fuel elements into the core, assigning the serial number of the "discharged" fuel element to the newly inserted fuel elements with a new enrichment. "In the multiple-cycle refueling mode, the fuel elements will repeatedly enter the core until the burnup reaches or exceeds the set discharge burnup threshold. Through steps A to D, the system first records the fuel parameters (position, serial number, burnup, etc.) of the discharged fuel, and then inserts new fuel elements into the core, repeating the process until the batch requirements are met. During the process, the fission inventory and the impurity activity release amount are dynamically calculated, and the results are stored in the second array. This per-cycle tracking and recording method can completely reproduce the nuclide evolution process of the fuel elements under multiple cycles, especially having key value for the accumulation of impurity activation and long-term fission yields. By accurately comparing the difference between the burnup and the discharge burnup, the retention or removal of the fuel can be dynamically determined, improving the fuel utilization rate and operation economy. At the same time, the data in the second array can provide a high-resolution source term basis for subsequent radiation dose management and spent fuel reprocessing.

[0038] In some alternative embodiments, step B includes: Assigning the unique identifier of the discharged fuel element model to the newly inserted fuel element model with a new enrichment.

[0039] In this embodiment, by assigning the unique identifier of the discharged fuel element to the newly inserted fuel element, the continuity of numbering and the unified management of the data chain are achieved. In this way, during multiple cycles, the historical trajectory of each fuel element can be continuously traced, and the data association will not be lost due to replacement operations. This measure realizes the full traceability of the fuel element life cycle and avoids data fragmentation caused by cyclic replacement. It can quickly locate the complete operation history of a certain fuel afterwards, greatly improving the management efficiency and compliance transparency.

[0040] In some alternative embodiments, step 107, by accumulating the fission inventory and the impurity activity release amount in the first array or the second array, obtains the calculation results of the core fission inventory and the impurity activity release amount, including: The fission stock and impurity activity release of all fuel element models in the first array are summed to obtain the calculated core model fission stock and impurity activity release. Alternatively, the fission stock and impurity activity release of all fuel element models in the second array can be summed to obtain the calculated fission stock and impurity activity release of the core model.

[0041] In this embodiment, the first array Q or the second array S corresponding to the total time Ti of the circulating flow process stores the numbers of all fuel elements in the current core. Based on the first array Q, the fission stock and impurity activity release corresponding to the stored fuel element numbers are obtained. The fission stock and impurity activity release of all fuel elements in the current core are accumulated to obtain the total core fission stock and impurity activity release. By accumulating the fission stock and impurity activity release data for each element and each time step in the first array Q or the second array S, the overall nuclide inventory and radioactive release of the core can be obtained as a macroscopic result. This process is equivalent to constructing a macroscopic total index based on microscopic modeling, realizing a result mapping from the unit level to the core level. This accumulation calculation method provides a high-precision and traceable assessment approach for core radioactive source terms. Compared with the traditional method using the average burnup model, this method can more realistically reflect the spatial-temporal distribution effects caused by fuel flow. Simultaneously, the accumulated data can also be directly used as input for environmental compliance assessment and report generation, improving operational safety and regulatory transparency.

[0042] In some alternative embodiments, Figure 3 This is a flowchart of the core fission stock and impurity activity release calculation system according to an embodiment of this disclosure; this application also provides a core fission stock and impurity activity release calculation system, including: Module 201 is used to construct a core model and multiple fuel element models using the target pebble bed reactor parameters and fuel element parameters, respectively. The filling module 202 is used to fill multiple fuel element models into the core model according to the loading amount based on fuel management parameters and to uniquely identify each fuel element model. The fuel management parameters include: refueling batch, fuel element loading amount and unloading burnup. The partitioning module 203 is used to control the circulation of fuel element models in the reactor core model and to divide the entire circulation process into multiple time steps. Calculation module 204 is used to calculate the fission stock and impurity activity release of each fuel element model within each time step using a unique identifier, and obtain the calculation results; The first storage module 205 is used to store the calculation results in the first array when the material replacement batch is once and the calculated effective growth factor meets the set threshold. The second storage module 206 is used to store the calculation results of each cycle flow in the second array when the refueling batch is at least twice and the fuel element model fuel consumption is greater than or equal to the unloading fuel consumption; The accumulation module 207 is used to obtain the calculation results of the core fission stock and impurity activity release by accumulating the fission stock and impurity activity release of the first array or the second array.

[0043] In this embodiment, by constructing a core geometric model and a fuel element model, and assigning a unique identifier to each fuel element, the core physics calculation program calculates the fission yield and impurity activation release on a per-element basis at the main / sub-time step. The calculation results are organized and accumulated according to a single-pass or multi-pass fuel management strategy. This overcomes the shortcomings of traditional static burnup distribution models in situations involving random fuel flow and historical power differences in pebble bed high-temperature gas-cooled reactors. This method can be used for fuel management optimization, maintenance dosage control, regulatory compliance, and long-term environmental assessment, and facilitates online decision-making, sensitivity analysis, and process optimization, thereby improving the safety, economy, and auditability of core operation. It achieves high-precision, traceable, and time-sequential calculation of core fission reserves and impurity activity release.

[0044] In one embodiment, this application also provides a computer device, including a memory and a processor, wherein the memory stores computer-readable instructions, and the processor executes the computer-readable instructions to perform the steps of calculating the core fission stock and the release of impurity activity.

[0045] In one embodiment, this application also provides a computer-readable storage medium storing computer-readable instructions, which, when executed by a processor, perform the steps of calculating the core fission stock and the release of impurity activity.

[0046] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0047] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calculating core fission stock and impurity activity release, characterized in that, include: The reactor core model and multiple fuel element models were constructed using the target pebble bed reactor parameters and fuel element parameters, respectively. According to the fuel management parameters, multiple fuel element models are filled into the core model according to the loading amount, and each fuel element model is uniquely identified. The fuel management parameters include: refueling batch, fuel element loading amount, and unloading burnup. The fuel element model is controlled to circulate in the reactor core model, and the entire process of the circulation is divided into multiple time steps; The fission stock and impurity activity release of each fuel element model within each time step are calculated using a unique identifier to obtain the calculation results; When the material replacement batch is once and the calculated effective growth factor meets the set threshold, the calculation result is stored in the first array; When the refueling batch is at least twice and the fuel element model fuel consumption is greater than or equal to the unloading fuel consumption, the calculation results of each cycle flow are stored in the second array; The core fission stock and the impurity activity release are calculated by summing the fission stock and the impurity activity release of the first array or the second array.

2. The method for calculating the core fission stock and impurity activity release of a pebble bed type high-temperature reactor according to claim 1, characterized in that, The calculation of fission stock and impurity activity release for each fuel element model within each time step using a unique identifier, and the resulting calculations, include: The fission rate of the core material of the fuel element model, the fission rate of the free uranium content, the impurity activation release rate, and the total radioactivity generation rate are calculated using the unique identifier for each time step.

3. The method for calculating the core fission stock and impurity activity release of a pebble bed type high-temperature reactor according to claim 1, characterized in that, When the material replacement batch is once and the calculated effective growth factor meets the set threshold, the calculation result is stored in a first array, including: When the refueling batch is a single pass, the reactor's neutron balance is calculated based on the fission parameters of the fuel element model; The effective multiplication factor of the reactor core model is obtained based on the neutron budget balance calculation. When the core reaches equilibrium based on the effective multiplication factor and the set threshold, the calculation result is output and stored in the first array.

4. The method for calculating the core fission stock and impurity activity release of a pebble bed type high-temperature reactor according to claim 3, characterized in that, The step of determining whether the reactor core has reached equilibrium based on the effective multiplication factor and a set threshold includes: When the difference between the effective multiplication factor in two consecutive time steps is less than or equal to a set threshold, the reactor core is determined to be in a balanced state.

5. The method for calculating the core fission stock and impurity activity release of a pebble bed type high-temperature reactor according to claim 1, characterized in that, When the refueling batch is at least twice and the fuel element model fuel consumption is greater than or equal to the unloading fuel consumption, the calculation results of each cycle flow are stored in a second array, including: Step A: Store the calculation results of the initial loop flow in the second array; Step B: Input the new enriched fuel element model into the core model after unloading the fuel element model; Step C: Obtain the fuel element model burnup and the unloading burnup parameters after at least two refueling cycles of the reactor core model; Step D: Determine the difference between the fuel element model burnup and the unloading burnup. When the difference is negative, the fuel element model continues to cycle in the core model. When the difference is positive, unload each fuel element model and store the calculation result in the second array. Repeat steps B to D until the set refueling batch is met.

6. The method for calculating the core fission stock and impurity activity release of a pebble bed type high-temperature reactor according to claim 5, characterized in that, Step B includes: Assign a unique identifier to the new enrichment fuel element model that has been removed from the fuel element model.

7. The method for calculating the core fission stock and impurity activity release of a pebble bed type high-temperature reactor according to claim 1, characterized in that, The calculation results of the core fission stock and the impurity activity release amount obtained by summing the fission stock and the impurity activity release amount of the first array or the second array include: The fission stock and impurity activity release of all fuel element models in the first array are summed to obtain the calculated core model fission stock and impurity activity release. Alternatively, the fission stock and impurity activity release of all fuel element models in the second array can be summed to obtain the calculated fission stock and impurity activity release of the core model.

8. A system for calculating core fission stock and impurity activity release, characterized in that, include: The building module is used to construct the core model and multiple fuel element models using the target pebble bed reactor parameters and fuel element parameters, respectively. The filling module is used to fill multiple fuel element models into the core model according to the loading amount based on fuel management parameters and to uniquely identify each fuel element model. The fuel management parameters include: refueling batch, fuel element loading amount, and unloading burnup. The partitioning module is used to control the circulation of the fuel element model in the reactor core model and to divide the entire circulation process into multiple time steps. The calculation module is used to calculate the fission stock and impurity activity release of each fuel element model within each time step using a unique identifier, and obtain the calculation results. The first storage module is used to store the calculation result in a first array when the material replacement batch is once and the calculated effective proliferation factor meets a set threshold. The second storage module is used to store the calculation results of each cycle flow in a second array when the refueling batch is at least twice and the fuel element model fuel consumption is greater than or equal to the unloading fuel consumption; The accumulation module is used to obtain the calculation results of the core fission stock and the impurity activity release by accumulating the fission stock and the impurity activity release of the first array or the second array.

9. A computer device, characterized in that, It includes a memory and a processor, wherein the memory stores computer-readable instructions, and the processor executes the computer-readable instructions to perform the steps of calculating the core fission stock and impurity activity release as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-readable instructions, which, when executed by a processor, perform the steps of calculating the core fission stock and impurity activity release as described in any one of claims 1 to 7.

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