Method and apparatus for evaluating long-term low-power operation days of a nuclear reactor core

Abstract

This application relates to a method and apparatus for assessing the number of long-term low-power operating days of a nuclear reactor core. The method includes: calculating the base load power operating history of the nuclear reactor core of a target unit based on the fuel management method of the normal cycle, and determining multiple target transient operating conditions; performing long-term low-power day analysis on the base load power operating history and the target transient operating conditions of the normal cycle to obtain a first long-term low-power operating day count; performing long-term low-power day analysis on the base load power operating history and the target transient operating conditions of the refueling cycle to obtain a second long-term low-power operating day count; determining whether the first long-term low-power operating day count is less than the second long-term low-power operating day count, and if so, using the first long-term low-power operating day count as the long-term low-power operating day count. This method enables rapid and comprehensive assessment of the number of long-term low-power operating days of a nuclear reactor core.

Description

Technical Field

[0001] This application relates to the field of nuclear reactor technology, and in particular to a method and apparatus for assessing the number of days a nuclear reactor core can operate at low power for an extended period. Background Technology

[0002] To cope with sudden power reduction requirements at nuclear power plants, such as generator set failures, the generator sets need to be quickly reduced from full power to low power and kept running for a period of time.

[0003] At this point, the nuclear power plant needs to assess the number of days the reactor core will operate at low power for an extended period. Low-power operation can only proceed if the actual required number of days of power reduction does not exceed the assessed upper limit for long-term low-power operation. The most important part of the assessment process is the risk assessment of the pellet-cladding interaction (PCI).

[0004] However, nuclear power plants need to respond quickly to sudden power reduction requirements, but existing methods for assessing long-term low-power operation days are time-consuming to calculate, and the assessed long-term low-power operation days for normal cycles may not cover the long-term low-power operation days for refueling cycles, thus failing to meet the actual needs of nuclear power plants. Summary of the Invention

[0005] Therefore, it is necessary to provide a method and apparatus for rapidly and comprehensively assessing the number of days a nuclear reactor core can operate at low power for an extended period, in order to address the aforementioned technical problems.

[0006] Firstly, this application provides a method for assessing the number of days a nuclear reactor core can operate at low power for an extended period, including:

[0007] Based on the normal cycle fuel management method, calculate the base load power operation history of the nuclear reactor core of the target unit and determine multiple target transient operating conditions;

[0008] Long-term low-power days were analyzed based on the base load power operation history and the target transient operating conditions of the nuclear reactor core under normal cycle to obtain the first long-term low-power operation days.

[0009] A long-term low-power day analysis was performed on the base load power operation history and the target transient operating conditions of the nuclear reactor core under refueling cycle to obtain the second long-term low-power operation days.

[0010] Determine whether the first long-term low-power operation days are less than the second long-term low-power operation days. If the first long-term low-power operation days are less than the second long-term low-power operation days, the first long-term low-power operation days shall be taken as the long-term low-power operation days of the nuclear reactor core.

[0011] In one embodiment, the base load power operating history of the target unit's nuclear reactor core is calculated based on the normal cycle fuel management method, including:

[0012] With the target unit operating at full power, the complete fuel cycle of the nuclear reactor core is executed according to the normal fuel management method to obtain the base load power operation history of the nuclear reactor core.

[0013] In one embodiment, a long-term low-power days analysis is performed on the base load power operation history and the target transient operating condition of the nuclear reactor core under normal cycle to obtain the first long-term low-power operation days, including:

[0014] Based on the base load power operating history, the core state with a specific burnup in the nuclear reactor core is selected;

[0015] Based on the core condition, calculate the internal pressure of the fuel rods, the fission gas release rate, and the contact pressure between the core and the cladding in the nuclear reactor core.

[0016] Obtain the three-dimensional power of the target transient condition under normal cycle, and calculate the PCI margin of the target transient condition under normal cycle based on the fuel rod internal pressure, fission gas release rate, contact pressure and the three-dimensional power.

[0017] When the target unit is operating at low power, the time required for the reactor core to consume the target transient PCI margin is assessed, and this time is used as the first long-term low-power operation days.

[0018] In one embodiment, the base load power operating history includes multiple burnups of the nuclear reactor core and core states corresponding to the multiple burnups; based on the base load power operating history, the core state of a specific burnup in the nuclear reactor core is selected, including:

[0019] Determine the specific fuel consumption required from multiple fuel consumption options;

[0020] The core state corresponding to a specific burnup in the nuclear reactor core can be retrieved from multiple core states included in the base load power operation history.

[0021] In one embodiment, a long-term low-power days analysis is performed on the base load power operating history and the target transient operating conditions of the nuclear reactor core under refueling cycles to obtain a second long-term low-power operating day count, including:

[0022] Based on the base load power operating history, the core state with a specific burnup in the nuclear reactor core is selected;

[0023] Based on the core condition, calculate the internal pressure of the fuel rods, the fission gas release rate, and the contact pressure between the core and the cladding in the nuclear reactor core.

[0024] Obtain the three-dimensional power of the target transient condition under the refueling cycle, and calculate the PCI margin of the target transient under the refueling cycle based on the internal pressure of the fuel rod, the fission gas release rate, the contact pressure and the three-dimensional power.

[0025] When the target unit is operating at low power, the time required for the reactor core to consume the target transient PCI margin is assessed, and this time is used as the second long-term low-power operation days.

[0026] In one embodiment, the method further includes:

[0027] When the number of long-term low-power operation days is not applicable, obtain the target transient PCI margin of the nuclear reactor core under normal cycle.

[0028] Based on the PCI margin of the target transient, a corresponding list of verification conditions is generated;

[0029] Based on the verification test case list, calculate the target number of days for long-term low-power operation of the nuclear reactor core.

[0030] In one embodiment, there are multiple target transients; based on the PCI margin of the target transients, a corresponding list of verification test conditions is generated, including:

[0031] For each target transient, the PCI margin of the target transient is classified according to power to obtain the PCI margin of the target transient under multiple power levels.

[0032] For each power, sort the target transient PCI margins under the power from smallest to largest, and select three PCI margins in sequence from the first one as the first PCI margin according to the sorting result.

[0033] Based on the first PCI margin and its variation pattern, and combined with engineering experience, multiple verification conditions are determined in the target transient condition, and a verification condition list is created based on the verification conditions.

[0034] In one embodiment, the method further includes:

[0035] If the first long-term low-power operation days are greater than the second long-term low-power operation days, a penalty is applied to the first long-term low-power operation days to obtain the third long-term low-power operation days.

[0036] Replace the third long-term low-power operation days with the first long-term low-power operation days, and return to the step of determining whether the first long-term low-power operation days are less than the second long-term low-power operation days to continue execution until the first long-term low-power operation days are less than the second long-term low-power operation days.

[0037] The first long-term low-power operation days, which are less than the second long-term low-power operation days, are taken as the long-term low-power operation days of the nuclear reactor core.

[0038] In one embodiment, penalizing the first long-term low-power operation days to obtain a third long-term low-power operation day includes:

[0039] The second PCI margin is obtained by reducing the PCI margin of the target transient corresponding to the first long-term low-power operation days.

[0040] When the target unit is operating at low power, assess the time required for the reactor core to consume the second PCI margin, and use this time as the third long-term low-power operation days corresponding to the second PCI margin.

[0041] Secondly, this application also provides a device for evaluating the long-term low-power operation days of a nuclear reactor core, comprising:

[0042] The determination module is used to calculate the base load power operating history of the nuclear reactor core of the target unit based on the normal cycle fuel management method, and to determine multiple target transient operating conditions;

[0043] The first analysis module is used to perform long-term low-power day analysis on the base load power operation history and the target transient operating conditions of the nuclear reactor core under normal cycle, and to obtain the first long-term low-power operation days.

[0044] The second analysis module is used to perform long-term low-power day analysis on the base load power operation history and the target transient operating conditions of the nuclear reactor core under refueling cycle, and to obtain the second long-term low-power operation days.

[0045] The envelope module is used to determine whether the first long-term low-power operation days are less than the second long-term low-power operation days. If the first long-term low-power operation days are less than the second long-term low-power operation days, the first long-term low-power operation days are taken as the long-term low-power operation days of the nuclear reactor core.

[0046] The aforementioned method and apparatus for assessing the long-term low-power operation days of a nuclear reactor core calculates the base load power operating history of the target unit's nuclear reactor core based on the normal cycle fuel management method and determines multiple target transient operating conditions. Since the target transient operating conditions need to cover all operating conditions of the nuclear power plant, the target transient operating conditions obtained through the above process can cover the complete operating power of the nuclear power plant. A long-term low-power operation day analysis is performed on the base load power operating history and the target transient operating conditions of the nuclear reactor core under normal cycle to obtain a first long-term low-power operation day; a second long-term low-power operation day analysis is performed on the base load power operating history and the target transient operating conditions of the nuclear reactor core under refueling cycle; it is then determined whether the first long-term low-power operation day is less than the second long-term low-power operation day. If the first long-term low-power operation day is less than the second long-term low-power operation day, the first long-term low-power operation day is taken as the long-term low-power operation day of the nuclear reactor core. In the above process, since the first long-term low-power operation days under normal cycle is less than the second long-term low-power operation days under material change cycle, it can be determined that the first long-term low-power operation days at this time simultaneously meet the actual requirements for long-term low-power operation under both normal cycle and material change cycle. Therefore, the long-term low-power operation days obtained through the above process can encompass the long-term low-power operation days of both normal cycle and material change cycle. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is an application environment diagram of a method for assessing the number of days a nuclear reactor core operates at low power for an extended period, as illustrated in one embodiment.

[0049] Figure 2 This is a flowchart illustrating a method for assessing the number of days a nuclear reactor core operates at low power for an extended period, as described in one embodiment.

[0050] Figure 3 This is a flowchart illustrating a method for assessing the number of days a nuclear reactor core operates at low power for an extended period, as described in another embodiment.

[0051] Figure 4 This is a structural block diagram of a device for assessing the number of days a nuclear reactor core operates at low power for an extended period, as shown in one embodiment. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0053] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0054] The method for assessing the number of days a nuclear reactor core can operate at low power for an extended period, as provided in this application, can be applied to, for example... Figure 1 In the application environment shown, terminal 102 communicates with server 104 via a network. A data storage system can store the data that server 104 needs to process. The data storage system can be integrated onto server 104, or it can be located in the cloud or on another network server. Specifically, terminal 102 or server 104 executes a method for assessing the number of long-term low-power operation days of a nuclear reactor core. This method includes: calculating the base load power operation history of the nuclear reactor core of the target unit based on the fuel management method of the normal cycle, and determining multiple target transient operating conditions; performing a long-term low-power operation day analysis on the base load power operation history and the target transient operating conditions of the nuclear reactor core under normal cycle to obtain a first long-term low-power operation day; performing a long-term low-power operation day analysis on the base load power operation history and the target transient operating conditions of the nuclear reactor core under refueling cycle to obtain a second long-term low-power operation day; determining whether the first long-term low-power operation day is less than the second long-term low-power operation day; if the first long-term low-power operation day is less than the second long-term low-power operation day, using the first long-term low-power operation day as the long-term low-power operation day of the nuclear reactor core.

[0055] Terminal 102 can be, but is not limited to, various personal computers, laptops, smartphones, tablets, drones, low-altitude aircraft, IoT devices, and portable wearable devices. IoT devices can include smart speakers, smart TVs, smart air conditioners, smart in-vehicle devices, and projection equipment. Portable wearable devices can include smartwatches, smart bracelets, and head-mounted displays. Head-mounted displays can be virtual reality (VR) devices, augmented reality (AR) devices, and smart glasses. Server 104 can be a standalone physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing cloud computing services.

[0056] In one exemplary embodiment, such as Figure 2 As shown, a method for assessing the number of days a nuclear reactor core operates at low power for an extended period is provided, and this method is applied to... Figure 1 Taking terminal 102 as an example, the explanation includes the following steps 202 to 208. Wherein:

[0057] Step 202: Based on the normal cycle fuel management method, calculate the base load power operation history of the nuclear reactor core of the target unit and determine multiple target transient operating conditions.

[0058] The normal cycle fuel management mode refers to the fuel management mode operated according to the fuel management plan approved by the final safety analysis of the nuclear power plant. The normal cycle includes the initial cycle, transition cycle, balancing cycle, and flexibility cycle. The base load state of the nuclear reactor core refers to the stable full power state. The base load power operation history is the historical operation record of the nuclear reactor core under the base load state throughout the entire fuel cycle, including data such as the nuclear reactor core burnup, three-dimensional power, and core status.

[0059] For example, the target transient operating condition refers to the PCI transient operating condition. Based on the fuel management method of the normal cycle and the operating mode of the target unit, specific requirements are set for the normal operation, start-up and shutdown of the target unit in order to ensure the safe and reliable operation of the target unit in the nuclear power plant. PCI analysis is performed according to the specific requirements to ensure that even if a PCI transient occurs during normal operation of the nuclear power plant, it is safe. Therefore, the multiple target transient operating conditions determined by the analysis cover all operating conditions of the target unit.

[0060] Step 204: Analyze the long-term low-power days of the base load power operation history and the target transient operating conditions of the nuclear reactor core under normal cycle to obtain the first long-term low-power operation days.

[0061] The target transient refers to the PCI transient, which is a transient with a low PCI margin. These include the excessively increased steam flow (ELI), under-power runaway rod lift transient (URWP), and runaway transient (RD). The PCI margin of the target transient is the safety margin remaining before the fuel cladding fails due to interaction between the fuel pellet and the cladding under the target transient operating condition. The larger the PCI margin, the safer the fuel rods are during the target transient. The first long-term low-power operating days refers to the operating time required for the reactor core to complete normal cycles when the target unit is operating at low power.

[0062] For example, based on the base load power operating history, the initial state of the nuclear reactor core is obtained, and the three-dimensional power of the target transient condition under normal cycle is acquired. This three-dimensional power is then superimposed onto the initial state of the nuclear reactor core to calculate the remaining safety margin before PCI failure of the fuel cladding distance under the target transient condition, i.e., the PCI margin for the target transient. Based on the PCI margin for the target transient, the number of long-term low-power days is calculated to obtain the number of long-term low-power operating days corresponding to the PCI margin. A first long-term low-power operating day count that is less than the number of long-term low-power operating days corresponding to the PCI margin is then obtained.

[0063] Step 206: Analyze the long-term low-power days of the base load power operation history and the target transient operating conditions of the nuclear reactor core under refueling cycle to obtain the second long-term low-power operation days.

[0064] The refueling cycle refers to a fuel cycle in a nuclear power plant that deviates from the normal cycle due to on-site overhaul plans or other reasons. This typically occurs after the third fuel cycle of the nuclear reactor core. The second long-term low-power operation days refer to the operating time required for the nuclear reactor core to perform a refueling cycle when the target unit is operating at low power. There are multiple second long-term low-power operation days.

[0065] For example, based on the base load power operating history, the initial state of the nuclear reactor core is obtained. The three-dimensional power of the target transient condition under the refueling cycle is acquired. By superimposing the three-dimensional power of the target transient condition onto the initial state of the nuclear reactor core, the safety margin remaining before the fuel cladding distance fails under the target transient condition can be calculated, i.e., the PCI margin of the target transient condition. Based on the PCI margin of the target transient condition, the number of long-term low-power days is calculated to obtain the number of long-term low-power operating days corresponding to the PCI margin. A second long-term low-power operating day that can encompass the long-term low-power operating days corresponding to the PCI margin is then obtained.

[0066] Step 208: Determine whether the first long-term low-power operation days are less than the second long-term low-power operation days. If the first long-term low-power operation days are less than the second long-term low-power operation days, the first long-term low-power operation days shall be taken as the long-term low-power operation days of the nuclear reactor core.

[0067] Among them, the number of days of long-term low-power operation of the nuclear reactor core can encompass both the number of days of long-term low-power operation after normal cycle and refueling cycle.

[0068] For example, when all second long-term low-power operation days do not exceed the first long-term low-power operation days, the first long-term low-power operation days are taken as the long-term low-power operation days of the nuclear reactor core.

[0069] In the aforementioned method for assessing the long-term low-power operation days of a nuclear reactor core, the base load power operating history of the target unit's nuclear reactor core is calculated based on the fuel management method of the normal cycle, and multiple target transient operating conditions are determined. Since the target transient operating conditions need to cover all operating conditions of the nuclear power plant, the target transient operating conditions obtained through the above process can cover the complete operating power of the nuclear power plant. A long-term low-power operation day analysis is performed on the base load power operating history and the target transient operating conditions of the nuclear reactor core under normal cycle to obtain the first long-term low-power operation days; a second long-term low-power operation day analysis is performed on the base load power operating history and the target transient operating conditions of the nuclear reactor core under refueling cycle to obtain the second long-term low-power operation days; it is then determined whether the first long-term low-power operation days are less than the second long-term low-power operation days. If the first long-term low-power operation days are less than the second long-term low-power operation days, the first long-term low-power operation days are taken as the long-term low-power operation days of the nuclear reactor core. In the above process, since the first long-term low-power operation days are the number of days of long-term low-power operation under normal cycle, if this number is less than the second long-term low-power operation days under material change cycle, it can be determined that the first long-term low-power operation days simultaneously meet the actual requirements of long-term low-power operation under both normal cycle and material change cycle. Therefore, the long-term low-power operation days obtained through the above process can encompass the long-term low-power operation days of both normal cycle and material change cycle.

[0070] In an exemplary embodiment, the base load power operating history of the nuclear reactor core of the target unit is calculated according to the normal cycle fuel management method, including: when the target unit is operating at full power, performing a complete fuel cycle of the nuclear reactor core according to the normal cycle fuel management method to obtain the base load power operating history of the nuclear reactor core.

[0071] Full power refers to the power level of the target unit when it is continuously operating under the set rated operating conditions.

[0072] For example, the target unit is operated at full power in accordance with the normal cycle fuel management method, so that the nuclear reactor core performs a complete fuel cycle and the base load power operation history of the nuclear reactor core is obtained.

[0073] In this embodiment, by performing a complete fuel cycle of the nuclear reactor core under normal fuel management when the target unit is operating at full power, the base load power operating history of the nuclear reactor core can be obtained. This provides accurate and comprehensive basic data support for subsequent long-term low power day analysis, ensuring the reliability of the analysis process and the accuracy of the evaluation results.

[0074] In one embodiment, a long-term low-power days analysis is performed on the base load power operation history and the target transient condition of the nuclear reactor core under normal cycle to obtain a first long-term low-power operation day. This includes: selecting a core state with specific burnup in the nuclear reactor core based on the base load power operation history; calculating the fuel rod internal pressure, fission gas release rate, and contact pressure between the core pellets and cladding based on the core state; obtaining the three-dimensional power of the target transient condition under normal cycle; calculating the PCI margin of the target transient under normal cycle based on the fuel rod internal pressure, fission gas release rate, contact pressure, and the three-dimensional power; and assessing the time required for the nuclear reactor core to consume the target transient PCI margin when the target unit is operating at low power, and using this time as the first long-term low-power operation day.

[0075] Low power refers to the operating condition where the target unit operates at a power level significantly lower than its rated power level.

[0076] For example, the core state of a specific burnup in the nuclear reactor core can be queried from multiple core states included in the base load power operating history.

[0077] For example, based on the core condition, calculations are performed in a physical model to obtain the internal pressure of the fuel rods, the fission gas release rate, and the contact pressure between the core and the cladding of the nuclear reactor core.

[0078] For example, the transient three-dimensional power distribution is obtained, which reflects the target transient operating condition. Based on the fuel rod internal pressure, fission gas release rate, contact pressure, and three-dimensional power distribution, the PCI margin for the target transient is calculated. The PCI margin calculation refers to the process of quantitatively assessing the ability of the reactor core's fuel rods to resist failure due to the interaction between the fuel pellets and cladding under the target transient operating condition using a fuel performance analysis program, and characterizing the safety margin as the difference between the technical limit and the calculated value. The technical limit is the failure threshold of the reactor core, and the calculated value can be obtained by superimposing the transient three-dimensional power distribution on known fuel rod internal pressure, fission gas release rate, and contact pressure using a fuel performance analysis program.

[0079] For example, based on the number of long-term low-power operation days corresponding to all PCI margins, the PCI margin is subtracted by a unit PCI margin to obtain the number of operation days that can encompass all the first long-term low-power operation days, and this number of operation days is taken as the first long-term low-power operation days of the nuclear reactor core under normal cycle.

[0080] For example, based on core physics data and thermal-hydraulic data, a first preset model and a second preset model are calculated respectively to obtain the fission gas release rate of the nuclear reactor core and the contact pressure between the core pellets and the cladding. Based on the fission gas release rate of the nuclear reactor core and the fuel rod structural parameters, a third preset model is calculated to obtain the internal pressure of the fuel rods in the nuclear reactor core. The core state includes core physics data, thermal-hydraulic data, and fuel rod structural parameters. The first preset model can be a spherical grain diffusion model, the second preset model can be a thermo-mechanically coupled contact mechanics model, and the third preset model can be an ideal gas law.

[0081] In this embodiment, the process described above allows for the assessment of the time required to deplete the PCI margin and sets this as the first long-term low-power operation day. This approach fully considers the impact of low-power operation on core safety, making the assessment results more closely aligned with actual operating scenarios. It provides a more conservative and reliable reference for the safe operation of the nuclear reactor core, effectively mitigating safety risks that may arise from the lack of coverage of certain extreme operating conditions.

[0082] In an exemplary embodiment, the base load power operation history includes multiple burnouts of the nuclear reactor core and core states corresponding to the multiple burnouts; based on the base load power operation history, selecting the core state of a specific burnout in the nuclear reactor core includes: determining the required specific burnout among the multiple burnouts; and querying the core state corresponding to the specific burnout in the nuclear reactor core from the multiple core states included in the base load power operation history.

[0083] Alternatively, the fuel consumption corresponding to each time step can be used as the required specific fuel consumption, or multiple fuel consumptions at any time can be randomly selected as the required specific fuel consumption.

[0084] For example, the mapping relationship between core state and specific burnup is obtained, and based on the mapping relationship, the core state required for a specific burnup is queried from the base load power operation history.

[0085] In this embodiment, by accurately determining the required specific fuel consumption among multiple fuel consumptions and querying the corresponding core state from multiple core states included in the base load power operation history, targeted basic data can be provided for subsequent calculation of key parameters such as fuel rod internal pressure and fission gas release rate.

[0086] In an exemplary embodiment, a long-term low-power days analysis is performed on the base load power operation history and the target transient condition of the nuclear reactor core under refueling cycle to obtain a second long-term low-power operation days. This includes: selecting a core state with specific burnup in the nuclear reactor core based on the base load power operation history; calculating the fuel rod internal pressure, fission gas release rate, and contact pressure between the core pellets and cladding based on the core state; obtaining the three-dimensional power of the target transient condition under refueling cycle, and calculating the PCI margin of the target transient under refueling cycle based on the fuel rod internal pressure, the fission gas release rate, the contact pressure, and the three-dimensional power; and evaluating the time required for the nuclear reactor core to consume the PCI margin of the target transient condition when the target unit is operating at low power, and using this time as the second long-term low-power operation days.

[0087] In this embodiment, by performing separate calculations for the deviated fuel cycle such as the refueling cycle, the runtime corresponding to the PCI margin consumption under different refueling modes is obtained. This can be compared with the first long-term low-power operation days obtained under normal cycle, providing complete data support for the subsequent determination of the safety boundary with envelope, ensuring that the final operation day evaluation result can cover the safety requirements under different refueling scenarios, and further improving the conservatism and reliability of the evaluation result.

[0088] In one embodiment, the method further includes: obtaining the target transient PCI margin of the nuclear reactor core under normal cycle when the long-term low-power operation days are not applicable; generating a corresponding verification condition list based on the target transient PCI margin; and calculating the target long-term low-power operation days of the nuclear reactor core according to the verification condition list.

[0089] The verification condition list includes at least one verification condition, and the target long-term low-power operation days are the long-term low-power operation days under the current material change cycle determined based on the verification condition.

[0090] Optionally, in the process of analyzing the long-term low-power days of the base load power operation history and the target transient operating conditions of the nuclear reactor core under normal cycle to obtain the first long-term low-power operation days, the PCI margin of the target transient of the nuclear reactor core under normal cycle can be obtained.

[0091] Optionally, the inapplicability of long-term low-power operation days may be due to situations that do not meet the needs of nuclear power plants or users, or other situations that do not apply here.

[0092] For example, the target long-term low-power operation days of the nuclear reactor core are evaluated based on each verification condition in the verification condition list using a long-term low-power day calculation method.

[0093] In this embodiment, when the original long-term low-power operation days of the nuclear reactor cannot meet the actual safety requirements of operation, a recalculation can be carried out based on the verification condition list generated by the existing PCI margin. The verification analysis can be supplemented in a targeted manner, which can correct the possible deviations in the original evaluation scheme, further adapt to the special needs of different nuclear power plants in actual operation, and ensure that the final evaluation results always meet the safety specifications of nuclear power plant operation, thus ensuring the safety of the nuclear reactor core in the long-term low-power operation scenario.

[0094] In one embodiment, there are multiple target transients. Based on the PCI margin of the target transients, a corresponding verification condition list is generated, including: for each target transient, classifying the PCI margin of the target transient according to power to obtain the PCI margin of the target transient under multiple power levels; for each power level, sorting the PCI margin of the target transient under the power level from smallest to largest, and selecting three PCI margins sequentially from the first one as the first PCI margin according to the sorting result; based on the first PCI margin and the variation law of the first PCI margin, combined with engineering experience, determining multiple verification conditions in the target transient conditions, and creating a verification condition list based on the verification conditions.

[0095] The verification condition is one that maintains a small PCI margin under different fuel management methods.

[0096] Optionally, the number of first PCI margins and the number of verification conditions may or may not correspond one-to-one; this is not limited here.

[0097] For example, the PCI margin of the target transient can be classified according to different power levels. For instance, the PCI margin of the target transient with a power of 100% FP can be classified as the first type of PCI margin, the PCI margin of the target transient with a power of 75% FP as the second type of PCI margin, and the PCI margin of the target transient with a power of 50% FP as the third type of PCI margin. A sorting and selection operation is performed on each type of PCI margin to obtain multiple first PCI margins. Here, FP refers to full power.

[0098] For example, based on the first PCI margin and its variation pattern, and combined with engineering experience, multiple verification operating conditions corresponding to the first PCI margin are determined in the target transient operating condition, which can maintain a small PCI margin in different fuel management methods. A verification operating condition list is created based on the multiple verification operating conditions.

[0099] In this embodiment, for each target transient, the PCI margins of the transients are sorted from smallest to largest. Based on the sorting result, three PCI margins are selected sequentially from the first to the second as the first PCI margin, which can identify cases with relatively small safety margins in the target transient. Furthermore, by analyzing the first PCI margin and its variation patterns, and referring to experience accumulated in engineering practice, verification conditions corresponding to the first PCI margin are accurately determined within the target transient operating conditions. A significant characteristic of these verification conditions is that they maintain a small PCI margin under different fuel management methods. Based on these selected verification conditions, a verification condition list is finally created. This method of generating the verification condition list can specifically focus on critical operating conditions with low safety margins, ensuring that subsequent assessments can efficiently and accurately cover potentially risky scenarios, laying a solid foundation for the accurate assessment of the number of days the nuclear reactor core operates at low power for extended periods.

[0100] In one embodiment, the method further includes: if the first long-term low-power operation days are greater than the second long-term low-power operation days, penalizing the first long-term low-power operation days to obtain a third long-term low-power operation days; replacing the third long-term low-power operation days with the first long-term low-power operation days, and returning to the step of determining whether the first long-term low-power operation days are less than the second long-term low-power operation days to continue execution until the first long-term low-power operation days are less than the second long-term low-power operation days; and taking the first long-term low-power operation days that are less than the second long-term low-power operation days as the long-term low-power operation days of the nuclear reactor core.

[0101] Optionally, the purpose of penalizing the first long-term low-power operation days can be achieved by obtaining a third long-term low-power operation day that is smaller than the first long-term low-power operation day.

[0102] In this embodiment, when the first long-term low-power operation days fail to encompass the second long-term low-power operation days, the PCI margin of the target transient is actively reduced to obtain the second PCI margin, and then the corresponding third long-term low-power operation days are obtained and replaced with the original first long-term low-power operation days. This cyclical process of continuously performing the envelope judgment not only dynamically adjusts the safety boundary to ensure that the finally determined long-term low-power operation days can fully cover various low-power operation conditions that may occur in the refueling cycle, but also effectively avoids the problem of insufficient safety boundary due to an initially set PCI margin that is too high. This further improves the conservatism and safety of the nuclear reactor core long-term low-power operation days assessment results, and provides a more reliable basis for nuclear power plants to formulate reasonable operation plans and safety strategies.

[0103] In an exemplary embodiment, penalizing the first long-term low-power operation days to obtain a third long-term low-power operation days includes: reducing the target transient PCI margin corresponding to the first long-term low-power operation days to obtain a second PCI margin; and, when the target unit is operating at low power, evaluating the time required for the nuclear reactor core to consume the second PCI margin, and using the time as the third long-term low-power operation days corresponding to the second PCI margin.

[0104] For example, the reduction value of the PCI margin of the target transient corresponding to the first long-term low-power operation days can be appropriately selected. By appropriately reducing the PCI margin of the target transient corresponding to the first long-term low-power operation days, the second PCI margin can be obtained.

[0105] In this embodiment, the penalty process is completed by directly reducing the PCI margin of the original target transient. This directly reduces the safety margin available for consumption, resulting in a shorter and more conservative number of operating days. The operation logic is clear and conforms to the conservative requirements of the safety assessment. This gives the penalty process a clear physical meaning and does not introduce irrelevant adjustment deviations, ensuring the consistency and rationality of the entire cyclic adjustment process.

[0106] In one of the most specific embodiments, such as Figure 3 As shown, this application will use a pre-set unit as an example to illustrate a method for evaluating the number of days of long-term low-power operation of a nuclear reactor core.

[0107] First, based on the normal cycle fuel management method, the base load power operating history of the preset unit is obtained. Then, based on the normal cycle fuel management method and the nuclear power plant's operating mode, PCI transient operating conditions covering the nuclear power plant's operating conditions are generated.

[0108] Secondly, based on the base load power operating history of the preset units and the PCI transient operating conditions covering nuclear power plant operating conditions, a long-term low-power operation day analysis of the nuclear reactor core of the preset units was conducted. This yielded the PCI margin of the nuclear reactor core under normal cycle PCI transients and the long-term low-power operation days corresponding to each PCI margin. The first long-term low-power operation day under normal cycle was obtained for nuclear reactor cores with fewer than all long-term low-power operation days. The PCI transients of the preset units include ELI and RD.

[0109] Finally, the second long-term low-power operation days of the nuclear reactor core under refueling cycle are calculated to determine whether the first long-term low-power operation days are less than the second long-term low-power operation days.

[0110] If the first long-term low-power operation days are less than the second long-term low-power operation days, the first long-term low-power operation days shall be taken as the long-term low-power operation days of the nuclear reactor core.

[0111] If the first long-term low-power operation days are greater than the second long-term low-power operation days, reduce the target transient margin, obtain the third long-term low-power operation days corresponding to this margin, replace the third long-term low-power operation days with the first long-term low-power operation days, and return to the step of determining whether the first long-term low-power operation days are less than the second long-term low-power operation days to continue execution until the first long-term low-power operation days are less than the second long-term low-power operation days; the first long-term low-power operation days that are less than the second long-term low-power operation days are taken as the long-term low-power operation days of the nuclear reactor core under refueling cycle.

[0112] The above process can be used to calculate that the nuclear reactor core of the pre-designed unit will operate at low power for 30 days during the refueling cycle.

[0113] In addition, when the long-term low-power operation days are not applicable, based on the PCI margin obtained above and the variation pattern of the PCI margin, combined with engineering experience, a list of verification operating conditions for the preset units is generated. The specific list is shown in Tables 1 and 2.

[0114] Table 1 Verification Conditions When PCI Transient is ELI

[0115]

[0116] In the verification checklist, the PCI transient condition means: FP is full power, BLX is the beginning of the life cycle, MOL is the middle of the life cycle, EOL is the end of the life cycle, L is the left boundary of the operation chart, R is the axial power offset (AO) at the right boundary of the operation chart, RI is the R-bar at the insertion limit, and RO is the R-bar outside the core. Taking 75%FP_EOL_L-27.59_RI as an example, FP is full power, EOL is the end of the life cycle, L is the left boundary of the operation chart, -27.59 is the value corresponding to the left boundary of the operation chart, and RI is the R-bar at the insertion limit.

[0117] Based on the verification condition list, calculate the target long-term low-power operation days for the current refueling cycle of the nuclear reactor core.

[0118] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0119] Table 2 Verification Case List When PCI Transient is RD

[0120]

[0121] Based on the same inventive concept, this application also provides a device for assessing the long-term low-power operation days of a nuclear reactor core, used to implement the aforementioned method for assessing the long-term low-power operation days of a nuclear reactor core. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations in one or more embodiments of the device for assessing the long-term low-power operation days of a nuclear reactor core provided below can be found in the limitations of the method for assessing the long-term low-power operation days of a nuclear reactor core described above, and will not be repeated here.

[0122] In one exemplary embodiment, such as Figure 4 As shown, a device 400 for evaluating the number of days a nuclear reactor core operates at low power for an extended period is provided, comprising: a determination module 402, a first analysis module 404, a second analysis module 406, and an envelope module 408, wherein:

[0123] The determination module 402 is used to calculate the base load power operating history of the nuclear reactor core of the target unit based on the normal cycle fuel management method, and to determine multiple target transient operating conditions;

[0124] The first analysis module 404 is used to perform long-term low-power day analysis on the base load power operation history and the target transient operating condition of the nuclear reactor core under normal cycle, and to obtain the first long-term low-power operation days.

[0125] The second analysis module 406 is used to perform long-term low-power day analysis on the base load power operation history and the target transient operating conditions of the nuclear reactor core under refueling cycle, and to obtain the second long-term low-power operation days.

[0126] Envelope module 408 is used to determine whether the first long-term low-power operation days are less than the second long-term low-power operation days. If the first long-term low-power operation days are less than the second long-term low-power operation days, the first long-term low-power operation days are taken as the long-term low-power operation days of the nuclear reactor core.

[0127] In one embodiment, the determining module 402 is further configured to calculate the base load power operating history of the nuclear reactor core of the target unit based on the normal cycle fuel management method, and determine multiple target transient conditions.

[0128] In one embodiment, the first analysis module 404 is further configured to select a core state with specific burnup in the nuclear reactor core based on the base load power operating history; calculate the internal pressure of the fuel rods, the fission gas release rate, and the contact pressure between the core pellets and the cladding based on the core state; obtain the three-dimensional power of the target transient condition under normal cycle; calculate the PCI margin of the target transient under normal cycle based on the internal pressure of the fuel rods, the fission gas release rate, the contact pressure, and the three-dimensional power; and evaluate the time required for the nuclear reactor core to consume the PCI margin of the target transient condition when the target unit is operating at low power, and use the time as the first long-term low-power operation days.

[0129] In one embodiment, the first analysis module 404 is further configured to determine the required specific burnout among multiple burnouts; and to query the core state corresponding to the specific burnout in the nuclear reactor core from multiple core states included in the base load power operation history.

[0130] In one embodiment, the second analysis module 406 is further configured to select a core state with specific burnup in the nuclear reactor core based on the base load power operating history; calculate the internal pressure of the fuel rods, the fission gas release rate, and the contact pressure between the core pellets and the cladding based on the core state; obtain the three-dimensional power of the target transient condition under the refueling cycle; calculate the PCI margin of the target transient under the refueling cycle based on the internal pressure of the fuel rods, the fission gas release rate, the contact pressure, and the three-dimensional power; and evaluate the time required for the nuclear reactor core to consume the PCI margin of the target transient condition when the target unit is operating at low power, and use the time as the second long-term low-power operation days.

[0131] In one embodiment, the nuclear reactor core long-term low-power operation days assessment device 400 further includes a generation module, which is used to obtain the target transient PCI margin of the nuclear reactor core under normal cycle when the long-term low-power operation days are not applicable; generate a corresponding verification condition list based on the target transient PCI margin; and calculate the target long-term low-power operation days of the nuclear reactor core according to the verification condition list.

[0132] In one embodiment, the generation module is further configured to classify the PCI margin of each target transient according to power to obtain the PCI margin of the target transient under multiple power levels; for each power level, sort the PCI margin of the target transient under the power level from smallest to largest, and select three PCI margins in sequence as the first PCI margin based on the sorting result; based on the first PCI margin and the variation law of the first PCI margin, combined with engineering experience, determine multiple verification conditions in the target transient conditions, and create a verification condition list based on the verification conditions.

[0133] In one embodiment, the envelope module 408 is further configured to, when the first long-term low-power operation days are greater than the second long-term low-power operation days, penalize the first long-term low-power operation days to obtain a third long-term low-power operation days; replace the third long-term low-power operation days with the first long-term low-power operation days, and return to the step of determining whether the first long-term low-power operation days are less than the second long-term low-power operation days to continue execution until the first long-term low-power operation days are less than the second long-term low-power operation days; and use the first long-term low-power operation days, which are less than the second long-term low-power operation days, as the long-term low-power operation days of the nuclear reactor core.

[0134] In one embodiment, the envelope module 408 is further configured to reduce the target transient PCI margin corresponding to the first long-term low-power operation days to obtain a second PCI margin; when the target unit is operating at low power, the time required for the nuclear reactor core to consume the second PCI margin is evaluated, and the time is used as the third long-term low-power operation days corresponding to the second PCI margin.

[0135] Each module in the aforementioned nuclear reactor core long-term low-power operation days assessment device 400 can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0136] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0137] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0138] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for assessing the number of days a nuclear reactor core operates at low power for an extended period, characterized in that, The method includes: Based on the normal cycle fuel management method, calculate the base load power operation history of the nuclear reactor core of the target unit and determine multiple target transient operating conditions; A long-term low-power day analysis was performed on the base load power operation history and the target transient operating condition of the nuclear reactor core under normal cycle to obtain the first long-term low-power operation days. A long-term low-power day analysis was performed on the base load power operation history and the target transient operating conditions of the nuclear reactor core under refueling cycle to obtain the second long-term low-power operation days. Determine whether the first long-term low-power operation days are less than the second long-term low-power operation days. If the first long-term low-power operation days are less than the second long-term low-power operation days, the first long-term low-power operation days shall be taken as the long-term low-power operation days of the nuclear reactor core.

2. The method according to claim 1, characterized in that, The calculation of the base load power operating history of the target unit's nuclear reactor core based on the normal cycle fuel management method includes: With the target unit operating at full power, the complete fuel cycle of the nuclear reactor core is executed according to the normal fuel management method to obtain the base load power operating history of the nuclear reactor core.

3. The method according to claim 1, characterized in that, The analysis of the long-term low-power days of the base load power operation history and the target transient operating conditions of the nuclear reactor core under normal cycle is used to obtain the first long-term low-power operation days, including: Based on the base load power operating history, the core state with a specific burnup in the nuclear reactor core is selected; Based on the core condition, calculate the internal pressure of the fuel rods, the fission gas release rate, and the contact pressure between the core and the cladding of the nuclear reactor core. Obtain the three-dimensional power of the target transient condition under the normal cycle, and calculate the PCI margin of the target transient condition under the normal cycle based on the internal pressure of the fuel rod, the fission gas release rate, the contact pressure and the three-dimensional power. When the target unit is operating at low power, the time required for the nuclear reactor core to consume the target transient PCI margin is assessed, and this time is taken as the first long-term low-power operation days.

4. The method according to claim 3, characterized in that, The base load power operating history includes multiple burnups of the nuclear reactor core and core states corresponding to these burnups; the process of selecting the core state of a specific burnup in the nuclear reactor core based on the base load power operating history includes: Determine the specific fuel consumption required from among the multiple fuel consumption options; The core state corresponding to the specific burnup in the nuclear reactor core is retrieved from multiple core states included in the base load power operation history.

5. The method according to claim 1, characterized in that, The analysis of the long-term low-power days of the base load power operation history and the target transient operating conditions of the nuclear reactor core under refueling cycle yields the second long-term low-power operation days, including: Based on the base load power operating history, the core state with a specific burnup in the nuclear reactor core is selected; Based on the core condition, calculate the internal pressure of the fuel rods, the fission gas release rate, and the contact pressure between the core and the cladding of the nuclear reactor core. Obtain the three-dimensional power of the target transient condition under the refueling cycle, and calculate the PCI margin of the target transient under the refueling cycle based on the internal pressure of the fuel rod, the fission gas release rate, the contact pressure and the three-dimensional power; When the target unit is operating at low power, the time required for the nuclear reactor core to consume the target transient PCI margin is assessed, and this time is used as the second long-term low-power operation days.

6. The method according to claim 1, characterized in that, The method further includes: When the long-term low-power operation days are not applicable, obtain the target transient PCI margin of the nuclear reactor core under normal cycle. Based on the PCI margin of the target transient, a corresponding list of verification conditions is generated; Based on the verification operating condition list, calculate the target number of long-term low-power operation days for the nuclear reactor core.

7. The method according to claim 6, characterized in that, The number of target transients is multiple; the corresponding verification condition list is generated based on the PCI margin of the target transients, including: For each target transient, the PCI margin of the target transient is classified according to power to obtain the PCI margin of the target transient under multiple power levels; For each power, the PCI margins of the target transient under the power are sorted from smallest to largest. Based on the sorting result, three PCI margins are selected sequentially from the first one as the first PCI margin. Based on the first PCI margin and its variation pattern, and combined with engineering experience, multiple verification conditions are determined in the target transient condition, and a verification condition list is created based on the verification conditions.

8. The method according to claim 1, characterized in that, The method further includes: If the first long-term low-power operation days are greater than the second long-term low-power operation days, a penalty is applied to the first long-term low-power operation days to obtain the third long-term low-power operation days. Replace the third long-term low-power operation days with the first long-term low-power operation days, and return to the step of determining whether the first long-term low-power operation days are less than the second long-term low-power operation days to continue execution until the first long-term low-power operation days are less than the second long-term low-power operation days. The first long-term low-power operation days, which are less than the second long-term low-power operation days, shall be taken as the long-term low-power operation days of the nuclear reactor core.

9. The method according to claim 8, characterized in that, The step of penalizing the first number of long-term low-power operation days to obtain the third number of long-term low-power operation days includes: The second PCI margin is obtained by reducing the PCI margin of the target transient corresponding to the first long-term low-power operation days. When the target unit is operating at low power, the time required for the nuclear reactor core to consume the second PCI margin is evaluated, and the time is taken as the third long-term low-power operation days corresponding to the second PCI margin.

10. A device for assessing the number of days a nuclear reactor core operates at low power for an extended period, characterized in that, The device includes: The determination module is used to calculate the base load power operating history of the nuclear reactor core of the target unit based on the normal cycle fuel management method, and to determine multiple target transient operating conditions; The first analysis module is used to perform long-term low-power day analysis on the base load power operation history and the target transient operating condition of the nuclear reactor core under normal cycle, and to obtain the first long-term low-power operation days. The second analysis module is used to perform long-term low-power day analysis on the base load power operation history and the target transient operating conditions of the nuclear reactor core under refueling cycle, and to obtain the second long-term low-power operation days. The envelope module is used to determine whether the first long-term low-power operation days are less than the second long-term low-power operation days. If the first long-term low-power operation days are less than the second long-term low-power operation days, the first long-term low-power operation days are taken as the long-term low-power operation days of the nuclear reactor core.

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