Method for determining the power of heat generated by decay of a spent fuel assembly of a sodium-cooled fast reactor
By placing coolant within the measurement space and directly measuring the power of decay heat, the problem of high uncertainty in the calculation of decay heat of spent fuel assemblies in sodium-cooled fast reactors is solved, achieving more accurate heat determination and improving reactor safety and economy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA INSTITUTE OF ATOMIC ENERGY
- Filing Date
- 2026-04-01
- Publication Date
- 2026-06-26
AI Technical Summary
In the existing technology, the calculation of the decay heat of spent fuel assemblies in sodium-cooled fast reactors has a 20% uncertainty, which leads to an overly conservative design, increases costs, and may cause safety problems such as coolant overcooling.
By placing a coolant in the measurement space, measuring the heat dissipated from the space and the heat carried away by the coolant, and combining the wall temperature and coolant flow rate, the power of decay heat can be directly measured, reducing uncertainty.
It improves the accuracy of decay heat calculation, reduces the conservative margin in reactor design and construction, enhances safety and economy, and avoids the problem of coolant overcooling.
Smart Images
Figure CN122291118A_ABST
Abstract
Description
Technical Field
[0001] Embodiments of this application relate to the field of nuclear reactor monitoring, and in particular to a method for determining the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor. Background Technology
[0002] The statements herein are provided merely as background information in connection with this application and do not necessarily constitute prior art.
[0003] After a reactor is shut down, fission products, actinides, activated products of structural materials, and activated products of coolant continue to decay and release heat. Among these, the heat generated by the decay of fission products is the main source of heat generated by decay after a reactor shutdown.
[0004] When fissile nuclides undergo neutron fission, they instantaneously produce fission products. After the reactor is shut down, a large amount of these fission products remain within the spent fuel assemblies and continue to release heat generated during decay (i.e., decay heat). Therefore, to prevent excessive fuel temperature from damaging the cladding and causing radioactive material leakage, a cooling system is needed to remove the heat. Accurately determining the power of the decay heat is beneficial for rationally designing the cooling system capacity and operating parameters, ensuring the safety of spent fuel assembly storage and transportation. Summary of the Invention
[0005] A brief overview of this application is provided below to offer a basic understanding of certain aspects thereof. It should be understood that this overview is not an exhaustive summary of the application. It is not intended to identify key or essential parts of the application, nor is it intended to limit its scope. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.
[0006] An embodiment of this application provides a method for determining the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor, comprising the following steps: S10: placing the spent fuel assembly of the sodium-cooled fast reactor whose decay heat is to be determined into a measurement space; S20: placing a coolant in the measurement space, the coolant being configured to conduct away a portion of the decay heat generated by the spent fuel assembly; S30: determining the average temperature of the walls of the measurement space, determining the power of heat dissipation from the measurement space and the power of heat conducted away by the coolant; S40: determining the power of heat generated by the decay of the spent fuel assembly based on the power of heat dissipation from the measurement space and the power of heat conducted away by the coolant.
[0007] The method for determining the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor, provided by embodiments of this application, takes into account the power of heat dissipation from the measured space and the power of heat carried away by the coolant. This makes the determined power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor more accurate, reduces the uncertainty level, thereby reducing the design conservative margin of the reactor decay heat removal system, improving the economy of reactor design and construction, and avoiding safety problems such as coolant overcooling, thus improving reactor safety. Attached Figure Description
[0008] To further illustrate the above and other advantages and features of this application, the specific embodiments of this application will be described in more detail below with reference to the accompanying drawings. The drawings, together with the following detailed description, are included in and form a part of this specification. Elements having the same function and structure are indicated by the same reference numerals. It should be understood that these drawings only depict typical examples of this application and should not be considered as limiting the scope of this application.
[0009] Figure 1 This is a flowchart illustrating a method for determining the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor, as provided in an embodiment of this application. Figure 2 This is a schematic diagram of the measurement space for a method of determining the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor, as provided in an embodiment of this application.
[0010] Explanation of reference numerals in the attached figures: 10. Sodium-cooled fast reactor spent fuel assembly; 1. Spent fuel assembly fastener; 2. Container body; 3. Container temperature measuring device; 4. Coolant temperature measuring device; 5. Coolant flow measuring device; 6. Coolant storage device; 7. Coolant drive device. Detailed Implementation
[0011] Exemplary embodiments of this application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this application.
[0012] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the equipment structure and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.
[0013] The following disclosure provides several different implementations or examples for carrying out this application. To simplify the disclosure of this application, specific examples of components and methods are described below. Of course, these are merely examples and are not intended to limit this application. In the description of the embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0014] In determining the decay heat of sodium-cooled fast reactors, the decay heat of the reactor or individual components is mainly determined based on the reactor irradiation history, irradiation neutron flux, and composition of the fuel assemblies, using burnup analysis programs. However, because the actual neutron flux of the fuel assemblies may deviate from that of the burnup analysis programs, and because the fuel irradiation history is difficult to simulate accurately, the decay constants and decay energies required by the burnup analysis programs have a certain degree of uncertainty. This can lead to errors in the calculation and analysis of the decay heat of spent fuel assemblies. Current decay heat determination processes consider a 20% uncertainty, but this high uncertainty setting leads to overly conservative decay heat considerations, resulting in an overly conservative design of the reactor decay heat derivation system, increasing reactor construction costs, and potentially causing safety issues such as coolant overcooling.
[0015] To address the aforementioned problems, embodiments of this application provide a method for determining the power of the heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor. Figure 1 This is a schematic flowchart illustrating a method for determining the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor, as provided in an embodiment of this application. Figure 1 As shown, the method includes the following steps: S10: placing the spent fuel assembly of the sodium-cooled fast reactor whose decay heat is to be determined into the measurement space; S20: setting a coolant in the measurement space, the coolant being configured to conduct away a portion of the decay heat generated by the spent fuel assembly of the sodium-cooled fast reactor; S30: determining the average temperature of the walls of the measurement space, determining the power of heat dissipation from the measurement space and the power of heat conducted away by the coolant; S40: determining the power of the heat generated by the decay of the spent fuel assembly of the sodium-cooled fast reactor based on the power of heat dissipation from the measurement space and the power of heat conducted away by the coolant.
[0016] The method for determining the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor, provided by embodiments of this application, takes into account the power of heat dissipation from the measured space and the power of heat carried away by the coolant. This makes the determined power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor more accurate, reduces the uncertainty level, thereby reducing the design conservative margin of the reactor decay heat removal system, improving the economy of reactor design and construction, and avoiding safety problems such as coolant overcooling, thus improving reactor safety.
[0017] In some embodiments, step S30 further includes the following steps: S31: determining the mass flow rate of the coolant; S32: determining the temperature of the coolant flowing into the measurement space and the temperature of the coolant flowing out of the measurement space; S33: determining the power of the heat removed by the coolant based on the mass flow rate of the coolant, the temperature of the coolant flowing into the measurement space, and the temperature of the coolant flowing out of the measurement space. This allows for real-time monitoring of the heat removal of the coolant, thereby obtaining a more accurate power of the heat removed by the coolant, which is beneficial for timely reflection of heat power fluctuations caused by the internal state of the cooling system (e.g., abnormal coolant temperature, flow rate, etc.).
[0018] In some embodiments, step S30 further includes the following steps: S34: determining multiple measurement points in the measurement space; S35: determining the surface area and temperature corresponding to the multiple measurement points; S36: determining the average temperature of the wall of the measurement space based on the surface area and temperature corresponding to the multiple measurement points. By measuring the temperature of multiple points on the wall and calculating the average temperature, the heat exchange boundary conditions between the spent fuel assembly of the sodium-cooled fast reactor and the surrounding environment can be accurately reflected, providing more accurate data for determining the power work of heat dissipation in the measurement space.
[0019] In some embodiments, step S30 further includes: determining the heat dissipation power of the measurement space based on the average temperature of the wall of the measurement space and the ambient temperature. This can reflect whether the heat dissipation system can remove the decay heat in time, and thus infer the decay heat power distribution inside the spent fuel assembly of the sodium-cooled fast reactor.
[0020] In some embodiments, the power of the heat removed by the coolant, the mass flow rate of the coolant, the temperature of the coolant flowing into the measurement space, and the temperature of the coolant flowing out of the measurement space satisfy the following relationship: ;in, The power representing the amount of heat carried away by the coolant; This indicates the temperature at which the coolant flows out of the measuring space; This indicates the temperature at which the coolant flows into the measurement space; The mass flow rate of the coolant is represented by C; the specific heat capacity of the coolant is represented by C; and time is represented by t. The heat power carried away by the coolant can be accurately determined in this way, which is beneficial for further accurate determination of the overall decay heat power of spent fuel assemblies in sodium-cooled fast reactors.
[0021] In some embodiments, the surface area, temperature, and average temperature of the walls of the measurement space corresponding to multiple measurement points satisfy the following relationship: ;in, This represents the average temperature of the wall of the measurement space; i represents the serial number corresponding to the measurement point. This represents the temperature corresponding to the i-th measurement point; Let represent the surface area corresponding to the i-th measurement point; n represent the number of measurement points; and t represent time. The average temperature of the wall of the measurement space can be accurately determined in this way.
[0022] In some embodiments, the average temperature of the walls of the measurement space, the ambient temperature, and the power of heat dissipation from the measurement space satisfy the following relationship: ;in, This indicates the power of heat dissipation from the measured space; This indicates the average temperature of the walls of the measurement space; The ambient temperature is represented by t, and time is represented by t. The above method can accurately determine the power of heat dissipation in the measurement space, which is beneficial for further accurate determination of the overall decay heat power of spent fuel assemblies in sodium-cooled fast reactors.
[0023] In some embodiments, in step S40, the power of space heat dissipation, the power of heat carried away by coolant, and the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor satisfy the following relationship: ;in, The power representing the amount of heat carried away by the coolant; This indicates the power of heat dissipation from the measured space; The power of the heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor is represented by t, which represents time. By directly measuring the heat dissipation in the measurement space and the heat carried away by the coolant, the power of the heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor can be accurately determined, avoiding the errors of traditional estimation methods and providing reliable data support for spent fuel management. The method provided in this application can realize the direct measurement of decay heat power, which helps to effectively verify the decay heat power calculation program, thereby reducing the design conservative margin and reducing the dependence on theoretical models.
[0024] In some embodiments, in step S20, the coolant is set to have a stable temperature when flowing into the measurement space and a stable mass flow rate within the measurement space. This makes the temperature difference between the coolant flowing into and out of the measurement space more stable and accurate, and makes the power of the heat removed by the coolant determined based on the coolant temperature difference and the coolant mass flow rate more accurate.
[0025] In some embodiments, in step S20, the temperature of the coolant flowing out of the measurement space is set to not exceed a predetermined value. By setting the predetermined value as a safety limit, the flow of coolant can be adapted to actual working conditions, thereby improving the safety and stability of the measurement process.
[0026] In some embodiments, in step S34, multiple measurement points are set to be evenly distributed in the vertical and circumferential directions of the measurement space, so that the temperature distribution at different locations can be accurately obtained in the vertical and circumferential directions, thereby improving the accuracy of the average temperature of the wall of the measurement space determined therefrom.
[0027] Figure 2 This is a schematic diagram of the measurement space for a method of determining the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor, as provided in embodiments of this application. In some embodiments, such as... Figure 2 As shown, in step S10, the measurement space is equipped with a spent fuel assembly fixing component 1, a container body 2, and a container temperature measuring component 3. The container body 2 is configured to accommodate the sodium-cooled fast reactor spent fuel assembly 10, coolant, and spent fuel assembly fixing component 1. The spent fuel assembly fixing component 1 is used to place and fix the sodium-cooled fast reactor spent fuel assembly 10. The container temperature measuring component 3 is located outside the container body 2 and is used to measure the temperature of the wall of the container body 2. The above configuration enables the sodium-cooled fast reactor spent fuel assembly 10 to be stably installed inside the container body 2, thereby improving the stability of the measurement process.
[0028] In some embodiments, the container temperature measuring element 3 can be configured as multiple sets of thermocouples at different heights, with the thermocouples set at multiple measuring points, so that the thermocouples can acquire the temperature at different heights and orientations in the measuring space, thereby improving the measurement accuracy.
[0029] In some embodiments, in step S34, multiple groups of thermocouples can be arranged as follows: divided into 10 or more groups in the vertical direction, with at least 8 thermocouples in each group arranged in the circumferential direction. This can increase the distribution density of thermocouples in the measurement space and further improve the accuracy of the average temperature of the wall of the measurement space.
[0030] In some embodiments, such as Figure 2As shown, the measurement space is also equipped with a coolant temperature measuring device 4, a coolant flow measuring device 5, a heat exchanger, a coolant storage device 6, and a coolant driving device 7. The coolant temperature measuring device 4 is located at the position where the coolant flows out of the container body 2 and is used to measure the temperature of the coolant flowing out of the measurement space. The coolant flow measuring device 5 is configured to measure the flow rate of the coolant. The heat exchanger is configured to exchange heat with the coolant, dissipate excess heat, and ensure that the coolant does not overheat. The coolant storage device 6 is configured to store the coolant and accommodate excess coolant in abnormal situations. The coolant driving device 7 is configured to allow the coolant to flow into the container body 2. Through the above settings, the stable flow of the coolant can be ensured, the variables in the decay heat power determination process can be controlled, and the safety of the measurement process can be improved.
[0031] In some embodiments, a coolant temperature control element can also be provided in the measurement space. The coolant temperature control element can be located between the coolant storage unit 6 and the coolant drive unit 7, and connected to the coolant storage unit 6 and the coolant drive unit 7 through a pipeline, thereby controlling the temperature of the coolant flowing into the measurement space to a stable level (e.g., 20±1℃), thereby controlling the variables in the process of determining decay heat power and improving the accuracy of decay heat power.
[0032] In some embodiments, the container body 2 may be made of stainless steel, preferably 316H austenitic stainless steel; the coolant is preferably a liquid with good compatibility with 316H austenitic stainless steel, such as deionized water.
[0033] In some embodiments, the measurement space is further provided with a calibration device, which is configured to calibrate the coolant temperature measuring element 4, the container temperature measuring element 3, and the coolant flow measuring element 5. This can reduce the relative error in the process of determining the power of the heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor, and control the relative error within a predetermined allowable range. This improves the accuracy and repeatability of the measured data and enables continuous online measurement, so that the structure in the measurement space does not need to be frequently disassembled or the operation interrupted during the measurement process.
[0034] In some embodiments, in step S10, after the sodium-cooled fast reactor spent fuel assembly 10 is placed into the container body 2, the coolant storage unit 6 can be activated first to fill the coolant pipeline and discharge the gas, and the coolant drive unit 7 can be activated to adjust the coolant mass flow rate to a predetermined value (e.g., 2.5 kg / s). The coolant temperature control unit can be activated to control the temperature of the coolant flowing into the measurement space at a predetermined value, so that the data obtained by each component measurement is accurate and repeatable. The coolant temperature measuring unit 4, the container temperature measuring unit 3, and the coolant flow rate measuring unit 5 can be activated simultaneously, and the temperature of the coolant flowing into the measurement space, the temperature of the coolant flowing out of the measurement space, the coolant mass flow rate, the wall temperature of each measurement point, and the ambient temperature can be collected and recorded in real time at a frequency of once per second, thereby realizing real-time monitoring of the decay heat power of the sodium-cooled fast reactor spent fuel assembly.
[0035] Regarding the embodiments of this application, it should also be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other to obtain new embodiments.
[0036] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. The scope of protection of this application shall be determined by the scope of the claims.
Claims
1. A method for determining the power of heat generated by the decay of spent fuel assemblies in a sodium-cooled fast reactor, characterized in that, It includes the following steps: S10: Place the sodium-cooled fast reactor spent fuel assembly whose decay heat is to be determined into the measurement space; S20: A coolant is provided in the measurement space, the coolant being configured to conduct away a portion of the decay heat generated by the spent fuel assembly of the sodium-cooled fast reactor. S30: Determine the average temperature of the wall of the measurement space, and determine the power of heat dissipation of the measurement space and the power of heat carried away by the coolant; S40: Determine the power of the heat generated by the decay of the spent fuel assembly in the sodium-cooled fast reactor based on the power of heat dissipation from the measurement space and the power of heat carried away by the coolant.
2. The method according to claim 1, characterized in that, Step S30 also includes the following steps: S31: Determine the mass flow rate of the coolant; S32: Determine the temperature at which the coolant flows into the measuring space and the temperature at which it flows out of the measuring space; S33: Determine the power of the heat removed by the coolant based on the mass flow rate of the coolant, the temperature of the coolant flowing into the measuring space, and the temperature of the coolant flowing out of the measuring space.
3. The method according to claim 2, characterized in that, Step S30 also includes the following steps: S34: Determine multiple measurement points in the measurement space; S35: Determine the surface area and temperature corresponding to the plurality of measurement points; S36: Determine the average temperature of the wall of the measurement space based on the surface area and temperature corresponding to the plurality of measurement points.
4. The method according to claim 2 or 3, characterized in that, Step S30 also includes: The heat dissipation power of the measurement space is determined based on the average temperature of the walls of the measurement space and the ambient temperature.
5. The method according to claim 2, characterized in that, The power of the heat removed by the coolant, the mass flow rate of the coolant, the temperature of the coolant flowing into the measurement space, and the temperature of the coolant flowing out of the measurement space satisfy the following relationship: ； in, This indicates the power of the heat removed by the coolant; This indicates the temperature at which the coolant flows out of the measuring space; This indicates the temperature at which the coolant flows into the measuring space; The mass flow rate of the coolant is represented by C; the specific heat capacity of the coolant is represented by t; and time is represented by t.
6. The method according to claim 3, characterized in that, The surface area and temperature corresponding to the multiple measurement points, as well as the average temperature of the wall of the measurement space, satisfy the following relationship: ； in, The value represents the average temperature of the wall of the measurement space; i represents the serial number corresponding to the measurement point. This represents the temperature corresponding to the i-th measurement point; Let represent the surface area corresponding to the i-th measurement point; n represent the number of measurement points; and t represent time.
7. The method according to claim 4, characterized in that, The average temperature of the walls of the measurement space, the ambient temperature, and the heat dissipation power of the measurement space satisfy the following relationship: ； in, This indicates the power of heat dissipation in the measurement space; This indicates the average temperature of the walls of the measurement space; The ambient temperature is represented by t; time is represented by t.
8. The method according to any one of claims 1-7, characterized in that, In step S40, the power of heat dissipation from the measurement space, the power of heat carried away by the coolant, and the power of heat generated by the decay of spent fuel assemblies in the sodium-cooled fast reactor satisfy the following relationship: ； in, This indicates the power of the heat removed by the coolant; This indicates the power of heat dissipation in the measurement space; The power of the heat generated by the decay of the spent fuel assembly in the sodium-cooled fast reactor is represented by t; time is represented by t.
9. The method according to claim 1, characterized in that, In step S20, the coolant is configured to have a stable temperature when flowing into the measurement space and a stable mass flow rate within the measurement space.
10. The method according to claim 1, characterized in that, In step S20, The temperature at which the coolant flows out of the measuring space is set to not exceed a predetermined value.
11. The method according to claim 3, characterized in that, In step S34, the plurality of measurement points are arranged to be uniformly distributed in the vertical and circumferential directions of the measurement space.
12. The method according to claim 3, characterized in that, In step S10, the measurement space is equipped with a spent fuel assembly fixing component, a container body, and a container temperature measuring component. The container body is configured to accommodate the spent fuel assembly of the sodium-cooled fast reactor, the coolant, and the spent fuel assembly fixtures. The spent fuel assembly holder is used to place and secure the sodium-cooled fast reactor spent fuel assembly. The container temperature measuring device is disposed on the outside of the container body and is used to measure the temperature of the wall of the container body.
13. The method according to claim 12, characterized in that, The container temperature measuring device is configured with multiple sets of thermocouples at different heights, and the thermocouples are set at the multiple measuring points.
14. The method according to claim 12, characterized in that, The measurement space is also equipped with a coolant temperature measuring device, a coolant flow measuring device, a heat exchanger, a coolant storage device, and a coolant drive device. The coolant temperature measuring element is positioned at the location where the coolant flows out of the container body, and is used to measure the temperature of the coolant as it flows out of the measuring space. The coolant flow measurement device is configured to measure the flow rate of the coolant. The heat exchanger is configured to exchange heat with the coolant. The coolant storage unit is configured to store the coolant. The coolant drive is configured to allow the coolant to flow into the container body.
15. The method according to claim 14, characterized in that, The measurement space is also equipped with a calibration device, which is configured to calibrate the coolant temperature measuring element, the container temperature measuring element, and the coolant flow measuring element.