Method and device for determining an off-nominal bubble nucleate boiling protection setpoint

Abstract

This application belongs to the field of nuclear reactor engineering technology, specifically relating to a method and apparatus for determining the online protection setting value for deviation from the nucleus boiling ratio (DNBR). The method includes: processing the uncertainties of the main parameters required for online DNBR calculation using statistical methods to establish online DNBR safety limits; and determining the online DNBR protection setting value by combining the DNBR advance protection amount determined by accident analysis with the online DNBR safety limits. This method can more timely and accurately describe the reactor core's operating status and issue shutdown signals, improving the unit's economy and safety.

Description

Technical Field

[0001] This application belongs to the field of nuclear reactor engineering technology, specifically relating to a method and apparatus for determining the online protection setting value of the deviation from the nucleus boiling ratio. Background Technology

[0002] In the design of the nuclear island of a pressurized water reactor nuclear power plant, multiple safety measures have been considered to prevent the leakage of radioactive materials, namely, the fuel cladding, the primary circuit pressure boundary, and the containment structure—three safety barriers. The main function of the reactor protection system is to automatically shut down the reactor when the operating conditions of the nuclear power plant reach their operating limits, thereby ensuring the safety of these three barriers and the reactor itself.

[0003] To prevent departure from nucleate boiling (DNB) and fuel meltdown, existing designs typically employ over-temperature (ΔT) and over-power (ΔT) protection channels. These channels reflect the minimum departure from nucleate boiling ratio (DNBR) and line power density in the core based on the temperature difference between the reactor inlet and outlet. However, this reflection is indirect and conservative. With the development of nuclear power technology, a new reactor protection method—online line power density (LPD) and DNBR protection—has begun to be applied. This method limits LPD and DNBR to ensure fuel rod integrity. Compared to over-temperature (ΔT) and over-power (ΔT) protection, the biggest advantage of online LPD and DNBR protection is that it directly monitors the actual safety parameters related to the fuel cladding barrier, rather than indirectly monitoring them through intermediate parameters. Therefore, it can more accurately describe the core's operating status, has less computational uncertainty, and provides greater flexibility while ensuring safe operation. The setting of the DNBR online system's parameters is particularly important in ensuring that both safety and flexibility requirements are met. Summary of the Invention

[0004] The purpose of this application is to provide a method and apparatus for determining the online protection setting value of the deviation from the nucleation boiling ratio, thereby addressing the question of whether the requirements for safety and flexibility can be effectively met.

[0005] The technical solution to achieve the purpose of this application is as follows:

[0006] This application provides a method for determining the online protection setting value for deviation from the nucleation-boiling ratio, the method comprising:

[0007] The uncertainties of the main parameters required for online DNBR calculation are handled using statistical methods to establish online DNBR safety limits;

[0008] Based on the DNBR advance protection value determined by the accident analysis and the online DNBR safety limit, the DNBR online protection setting value is determined.

[0009] Optionally, the uncertainty of the main parameters required for online DNBR calculation is processed using statistical methods to establish online DNBR safety limits, specifically including:

[0010] For the parameters that need statistical processing, perform Monte Carlo sampling N times according to their respective statistical laws and characteristic parameters, and then perform N calculations to obtain N minimum DNBR values;

[0011] Determine the online DNBR safety limit based on N minimum DNBR values ​​and preset rules.

[0012] Optionally, the preset rules specifically include:

[0013] To ensure that the probability of the core DNBR exceeding a certain limit is 95% at a 95% confidence level, the following condition must be met at any location in the core:

[0014]

[0015] Where, q a,CHF q is the critical heat flux density of the segment. a Let I be the heat flux density of the segment, and I be the limit value.

[0016] Optionally, determining the online DNBR safety limit based on N minimum DNBR values ​​and preset rules specifically includes:

[0017] At a 95% confidence level, considering a 95% probability that DNBR is not lower than I, i.e., it is required that:

[0018]

[0019] in, σ is the average of N minimum DNBR values. total The standard deviation of the N smallest DNBR values;

[0020] When DNBR equals I, Formula 2 becomes an equation, that is:

[0021]

[0022] AL stands for Online DNBR Safety Limits.

[0023] Optionally, the main parameters required for the online DNBR calculation specifically include: reactor power, pressurizer pressure, reactor inlet temperature, nuclear enthalpy rise factor of the channel, and calculation uncertainty of the fast calculation module, among any one or more of these parameters.

[0024] Optional, N≥1000.

[0025] Optionally, determining the DNBR online protection setting value by combining the DNBR advance protection amount determined by accident analysis and the online DNBR safety limit specifically includes:

[0026] Based on the online DNBR protection delay and shutdown reactivity, the time Δt corresponding to ΔDNBR is determined to terminate the continued decline of DNBR.

[0027] Perform a transient accident simulation without reactor shutdown protection, and statistically analyze the change in DNBR value ΔDNBR within the range Δt before DNBR reaches the DNBR design limit;

[0028] ΔDNBR is added to the online DNBR safety setting value as the online protection setting value for the online DNBR.

[0029] Optionally, ΔDNBR is added to the online DNBR safety setting as the online protection setting value for the online DNBR, and the setting further includes:

[0030] The online DNBR protection setting value was ultimately determined by verifying the selected accident conditions.

[0031] Optionally, ΔDNBR is added to the online DNBR safety setting as the online protection setting value for the online DNBR, specifically including:

[0032] The online DNBR safety setting is supplemented by ΔDNBR, and a certain margin is considered as the accident analysis value of the online DNBR protection setting.

[0033] This application embodiment also provides a device for determining the online protection setpoint value of the deviation from the nucleation-boiling ratio, the device comprising:

[0034] The safety limit determination module is used to process the uncertainty of the main parameters required for online DNBR calculation using statistical methods to establish online DNBR safety limits;

[0035] The setting value determination module is used to determine the DNBR online protection setting value by combining the DNBR advance protection quantity determined by accident analysis and the online DNBR safety limit.

[0036] The beneficial technical effects of this application are as follows:

[0037] This application provides a method and apparatus for determining the online protection setpoint for deviation from the nucleus boiling ratio, providing real-time monitoring for reactor operation. It offers the following advantages:

[0038] (1) By combining the DNBR online monitoring system, the safety parameters related to the fuel cladding barrier can be directly monitored, which can describe the core operation status more timely and accurately, and provide greater flexibility for power plant operation while ensuring safe operation.

[0039] (2) Compared with the traditional method of using over-temperature ΔT and over-power ΔT protection channels to achieve core protection, it can describe the core's operating status more timely and accurately and issue shutdown signals, thereby improving the unit's economy and safety. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating a method for determining the online protection setting value of the deviation from the nucleation-boiling ratio, as provided in an embodiment of this application. Detailed Implementation

[0041] To enable those skilled in the art to better understand this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only a part of the embodiments of this application, and not all of them. Based on the embodiments described in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] When setting the DNBR online protection alarm setting value, uncertainties such as measurement and DNBR calculation need to be considered to ensure that the reactor fuel rods do not experience DNB when the online DNBR protection shutdown is triggered. This application provides an innovative approach to achieving real-time protection of reactor operation. An embodiment of this application provides a method and apparatus for determining the online protection setting value for deviation from the nucleus boiling ratio. This method uses statistical methods to analyze various uncertainties to establish DNBR safety limits, and combines this with the DNBR advance protection amount determined by accident analysis to determine the DNBR online protection setting value. Compared to the traditional method of using over-temperature ΔT and over-power ΔT protection channels for core protection, this method, applied to the DNBR online protection system, can more timely and accurately describe the core's operating status by directly monitoring safety parameters related to the fuel cladding barrier, thereby determining the timing of the shutdown. While ensuring safe operation, this method provides greater flexibility for power plant operation, thus aligning with the national strategic goals for nuclear power development and significantly enhancing my country's basic research and development level in nuclear power analysis and design technology.

[0043] Based on the above, in order to clearly and in detail illustrate the advantages of this application, the specific embodiments of this application will be described below in conjunction with the accompanying drawings.

[0044] See Figure 1The figure is a flowchart illustrating a method for determining the online protection setting value of the deviation from the nucleation boiling ratio provided in an embodiment of this application.

[0045] This application provides a method for determining the online protection setting value for deviation from the nucleation-boiling ratio, including:

[0046] S101: The uncertainty of the main parameters required for online DNBR calculation is handled using statistical methods to establish online DNBR safety limits;

[0047] S102: Determine the DNBR online protection setting value by combining the DNBR advance protection quantity determined by the accident analysis and the online DNBR safety limit.

[0048] In practical implementation, the main parameters required for online DNBR calculation may include any one or more of the following: reactor power, pressurizer pressure, reactor inlet temperature, nuclear enthalpy rise factor of the channel, and calculation uncertainty of the fast calculation module.

[0049] In some possible implementations of the embodiments of this application, step S101 specifically includes:

[0050] For the parameters requiring statistical processing, Monte Carlo sampling is performed N times (e.g., N≥1000) according to their respective statistical laws and characteristic parameters (such as mean, standard deviation, etc.). Then, N calculations are performed to obtain N minimum DNBR values. Statistical tests can verify that these N minimum DNBR values ​​are a set with a mean of DNBR (online calculated and displayed value) and a standard deviation of σ. total It follows a normal distribution.

[0051] Determine the online DNBR safety limit based on N minimum DNBR values ​​and preset rules.

[0052] In one example, the preset rules specifically include:

[0053] To ensure that the probability of the core DNBR exceeding a certain limit is 95% at a 95% confidence level, the following condition must be met at any location in the core:

[0054]

[0055] Where, q a,CHF q is the critical heat flux density of the segment. a Let I be the heat flux density of the segment, and I be the limit value.

[0056] As an example, based on N minimum DNBR values ​​and preset rules, the online DNBR security limit is determined, specifically including:

[0057] At a 95% confidence level, considering a 95% probability that DNBR is not lower than I, i.e., it is required that:

[0058]

[0059] in, σ is the average of N minimum DNBR values. total The standard deviation of the N smallest DNBR values;

[0060] When DNBR equals I, Formula 2 becomes an equation, that is:

[0061]

[0062] AL stands for Online DNBR Safety Limits.

[0063] In some possible implementations of the embodiments of this application, step S102 specifically includes:

[0064] Based on the online DNBR protection delay and shutdown reactivity, the time Δt corresponding to ΔDNBR is determined to terminate the continued decline of DNBR.

[0065] Perform a transient accident simulation without reactor shutdown protection, and statistically analyze the change in DNBR value ΔDNBR within the range Δt before DNBR reaches the DNBR design limit;

[0066] ΔDNBR is added to the online DNBR safety setting value as the online protection setting value for the online DNBR.

[0067] In one example, ΔDNBR is added to the online DNBR safety setting as the online protection setting value for the online DNBR, followed by:

[0068] The online DNBR protection setting value was ultimately determined by verifying the selected accident conditions.

[0069] As an example, ΔDNBR is added to the online DNBR safety setting as the online protection setting value for the online DNBR, specifically including:

[0070] The online DNBR safety setting is supplemented by ΔDNBR, and a certain margin is considered as the accident analysis value of the online DNBR protection setting.

[0071] In a specific example, an online DNBR calculation program was used to determine the online DNBR protection setting using statistical methods.

[0072] Next, the accidents requiring online DNBR protection are identified, and the ΔDNBR that needs to be triggered in advance is determined. The overall method is as follows:

[0073] 1) Determine the time Δt corresponding to ΔDNBR based on the online DNBR protection delay and the reactor shutdown reactivity to terminate the DNBR's continued decline time;

[0074] 2) Conduct a transient simulation of an accident without reactor shutdown protection, and statistically analyze the change in DNBR within the range of Δt before DNBR reaches its design limit (i.e., ΔDNBR);

[0075] 3) Add ΔDNBR to the online DNBR safety setting, and consider a certain margin as the accident analysis value of the online DNBR protection setting.

[0076] After determining the fault analysis values ​​of the online DNBR protection settings, the values ​​are verified through selected fault conditions to finally determine the fault analysis values ​​of the online DNBR protection settings.

[0077] This application provides a method for determining the online protection setting value for deviation from the nucleus boiling ratio (DNBR), offering an innovative approach to achieving real-time protection of reactor operation. It employs statistical methods to analyze various uncertainties and establish DNBR safety limits. Combined with DNBR advance protection parameters determined through accident analysis, the online protection setting value for the DNBR is then determined. Compared to using over-temperature ΔT and over-power ΔT protection channels for core protection, this method, applied to the DNBR online protection system, directly monitors safety parameters related to the fuel cladding barrier, enabling more timely and accurate description of the core's operating status and the issuance of shutdown signals, thereby improving reactor economy and safety.

[0078] Based on the above embodiments, which provide a method for determining the online protection setting value of the deviation from the nucleation-boiling ratio, this application also provides a device for determining the online protection setting value of the deviation from the nucleation-boiling ratio.

[0079] This application provides an embodiment of an online protection setting value determination device for deviation from the nucleation-boiling ratio, comprising:

[0080] The safety limit determination module is used to process the uncertainty of the main parameters required for online DNBR calculation using statistical methods to establish online DNBR safety limits;

[0081] The setting value determination module is used to determine the DNBR online protection setting value by combining the DNBR advance protection quantity determined by accident analysis and the online DNBR safety limit.

[0082] In some possible implementations of the embodiments of this application, the security limit determination module is specifically used for:

[0083] For the parameters that need statistical processing, perform Monte Carlo sampling N times according to their respective statistical laws and characteristic parameters, and then perform N calculations to obtain N minimum DNBR values;

[0084] Determine the online DNBR safety limit based on N minimum DNBR values ​​and preset rules.

[0085] In one example, the preset rules specifically include:

[0086] To ensure that the probability of the core DNBR exceeding a certain limit is 95% at a 95% confidence level, the following condition must be met at any location in the core:

[0087]

[0088] Where, q a,CHF q is the critical heat flux density of the segment. a Let I be the heat flux density of the segment, and I be the limit value.

[0089] In some possible implementations of the embodiments of this application, the security limit determination module is specifically used for:

[0090] At a 95% confidence level, considering a 95% probability that DNBR is not lower than I, i.e., it is required that:

[0091]

[0092] in, σ is the average of N minimum DNBR values. total The standard deviation of the N smallest DNBR values;

[0093] When DNBR equals I, Formula 2 becomes an equation, that is:

[0094]

[0095] AL stands for Online DNBR Safety Limits.

[0096] In one example, the main parameters required for the online DNBR calculation specifically include any one or more of the following: reactor power, pressurizer pressure, reactor inlet temperature, nuclear enthalpy rise factor of the channel, and computational uncertainty of the fast calculation module.

[0097] As an example, N ≥ 1000.

[0098] In some possible implementations of the embodiments of this application, the setpoint determination module is specifically used for:

[0099] Based on the online DNBR protection delay and shutdown reactivity, the time Δt corresponding to ΔDNBR is determined to terminate the continued decline of DNBR.

[0100] Perform a transient accident simulation without reactor shutdown protection, and statistically analyze the change in DNBR value ΔDNBR within the range Δt before DNBR reaches the DNBR design limit;

[0101] ΔDNBR is added to the online DNBR safety setting value as the online protection setting value for the online DNBR.

[0102] In one example, the setpoint determination module is also specifically used for:

[0103] The online DNBR protection setting value was ultimately determined by verifying the selected accident conditions.

[0104] As an example, the setpoint determination module is also specifically used for:

[0105] The online DNBR safety setting is supplemented by ΔDNBR, and a certain margin is considered as the accident analysis value of the online DNBR protection setting.

[0106] The present application has been described in detail above with reference to the accompanying drawings and embodiments. However, the present application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present application. All content not described in detail in this application can be derived from existing technology.

Claims

1. A method for determining the online protection setting value for deviation from the nucleation boiling ratio, characterized in that, The method includes: The uncertainties of the main parameters required for online DNBR calculation are handled using statistical methods to establish online DNBR safety limits; Based on the DNBR advance protection value determined by the accident analysis and the online DNBR safety limit, determine the DNBR online protection setting value; The determination of the DNBR online protection setting value, based on the DNBR advance protection quantity determined by accident analysis and the online DNBR safety limit, specifically includes: Based on the online DNBR protection delay and shutdown reactivity, the time Δt corresponding to ΔDNBR is determined to terminate the continued decline of DNBR. Perform a transient accident simulation without reactor shutdown protection, and statistically analyze the change in DNBR within the range of Δt before DNBR reaches the DNBR design limit; ΔDNBR is added to the online DNBR safety setting value as the online protection setting value for the online DNBR; The online DNBR safety setting is supplemented by ΔDNBR as the online protection setting value for the online DNBR, and then the following is also included: The online DNBR protection setting value was ultimately determined by verifying the selected accident conditions.

2. The method for determining the online protection setting value of the deviation from the nucleus boiling ratio according to claim 1, characterized in that, The uncertainty of the main parameters required for online DNBR calculation is handled using statistical methods to establish online DNBR safety limits, specifically including: For the parameters that need statistical processing, perform Monte Carlo sampling N times according to their respective statistical laws and characteristic parameters, and then perform N calculations to obtain N minimum DNBR values; Determine the online DNBR safety limit based on N minimum DNBR values ​​and preset rules.

3. The method for determining the online protection setting value of the deviation from the nucleus boiling ratio according to claim 2, characterized in that, The preset rules specifically include: To ensure that the probability of the core DNBR exceeding a certain limit is 95% at a 95% confidence level, the following condition must be met at any location in the core: (Official 1) in, The critical heat flux density of the segment. Let I be the heat flux density of the segment, and I be the limit value.

4. The method for determining the online protection setting value of the deviation from the nucleus boiling ratio according to claim 3, characterized in that, The determination of online DNBR safety limits based on N minimum DNBR values ​​and preset rules specifically includes: At a 95% confidence level, considering a 95% probability that DNBR is not lower than I, that is, it is required that: (Official 2) in, The average of N minimum DNBR values. The standard deviation of the N smallest DNBR values; When DNBR equals I, Formula 2 becomes an equation, that is: (Official 3) AL stands for Online DNBR Safety Limits.

5. The method for determining the online protection setting value of the deviation from the nucleus boiling ratio according to claim 1, characterized in that, The main parameters required for the online DNBR calculation specifically include: reactor power, pressurizer pressure, reactor inlet temperature, channel nuclear enthalpy rise factor, and any one or more of the calculation uncertainties of the fast calculation module.

6. The method for determining the online protection setting value of the deviation from the nucleus boiling ratio according to claim 2, characterized in that, N≥1000。 7. The method for determining the online protection setting value of the deviation from the nucleus boiling ratio according to claim 1, characterized in that, The online DNBR safety setting is supplemented by ΔDNBR, which serves as the online protection setting value for the online DNBR. Specifically, this includes: The online DNBR safety setting is supplemented by ΔDNBR, and a certain margin is considered as the accident analysis value of the online DNBR protection setting.

8. A device for determining the online protection setpoint value for deviation from the nucleation boiling ratio, characterized in that, The device includes: The safety limit determination module is used to process the uncertainty of the main parameters required for online DNBR calculation using statistical methods to establish online DNBR safety limits; The setting value determination module is used to determine the DNBR online protection setting value by combining the DNBR advance protection quantity determined by accident analysis and the online DNBR safety limit; The determination of the DNBR online protection setting value, based on the DNBR advance protection quantity determined by accident analysis and the online DNBR safety limit, specifically includes: Based on the online DNBR protection delay and shutdown reactivity, the time Δt corresponding to ΔDNBR is determined to terminate the continued decline of DNBR. Perform a transient accident simulation without reactor shutdown protection, and statistically analyze the change in DNBR within the range of Δt before DNBR reaches the DNBR design limit; ΔDNBR is added to the online DNBR safety setting value as the online protection setting value for the online DNBR; The online DNBR safety setting is supplemented by ΔDNBR as the online protection setting value for the online DNBR, and then the following is also included: The online DNBR protection setting value was ultimately determined by verifying the selected accident conditions.

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