Method, device and storage medium for supervising a lower limit value of a moderator temperature coefficient

Abstract

The present application relates to a kind of moderator temperature coefficient lower limit value supervision method, device and storage medium, comprising: the supervision model for establishing in advance for characterizing the corresponding relationship between reactor operating parameter and moderator temperature coefficient lower limit value;At least including the online monitoring parameter of core average temperature, control rod insertion depth and core flow during reactor operation is collected;Online monitoring parameter is input into the supervision model, determines the risk state of current operating condition corresponding moderator temperature coefficient, and judges whether the risk of moderator temperature coefficient exists breakthrough preset safety limit value;When determining that there is risk, output early warning information and / or control reactor adjusts to safe operating state.The present application realizes the online supervision of moderator temperature coefficient lower limit value by non-invasive parameter threshold comparison, without introducing disturbance to core, avoids the safety risk and power generation loss caused by traditional measurement method, improves the real-time performance and reliability of safety supervision.

Description

Technical Field

[0001] This invention relates to the technical field of nuclear power plant operation, and more specifically, to a method, apparatus, and storage medium for monitoring the lower limit of the moderator temperature coefficient. Background Technology

[0002] The lower limit of the moderator temperature coefficient (MTC) is an input assumption in the nuclear power plant safety analysis report, a safety limit for reactor operation, and the ultimate boundary for safe operation of the nuclear power plant. To ensure the validity of the assumptions in the safety analysis report and to guarantee that the prescribed safety limits are not exceeded during nuclear power plant operation, the lower limit of the moderator temperature coefficient should be monitored and managed during reactor operation.

[0003] Currently, there are three main test methods for measuring the temperature coefficient of moderators: First, the rod adjustment method, which involves adjusting the position of the control rod to cause a significant change in the temperature of the moderator, thereby measuring the temperature coefficient of the moderator.

[0004] Second, the power adjustment method, which involves indirectly measuring the temperature coefficient of the moderator by rapidly changing the power level.

[0005] Third, the cooling method involves not adding water to the reactor, not tracking the temperature of the control rods, keeping the boron concentration constant, measuring the change of the moderator with temperature, and finally compensating for the average temperature effect of the moderator by rapidly adjusting the insertion depth of the control rods.

[0006] However, the moderator temperature coefficient generally becomes more and more negative as reactor burnup increases, so the closer to the end of the reactor's lifespan, the closer the moderator temperature coefficient is to the lower limit.

[0007] The current mainstream testing methods for measuring the moderator temperature coefficient all require introducing disturbances into the reactor core. The closer to the end of the reactor's lifespan, the more likely it is to cause uncontrollable xenon oscillations, which could affect the safety of the reactor core.

[0008] Furthermore, relevant nuclear safety guidelines require that if, for some reason, operators are unaware of the operating status, cannot determine whether the nuclear power plant is operating within its limits, or if the plant is operating in an unexpected manner, measures should be taken promptly to bring the plant back to a safe state. Near the end of its service life and when moderator temperature coefficient measurements are not possible, operators cannot ascertain the actual state of the in-reactor moderator temperature coefficient and cannot determine whether the assumptions of the safety analysis still encompass the actual reactor state.

[0009] Therefore, a new solution is needed. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a method, apparatus and storage medium for monitoring the lower limit of the temperature coefficient of a moderator, in order to address the deficiencies of the prior art.

[0011] The technical solution adopted by this invention to solve its technical problem is: to construct a method for monitoring the lower limit of the temperature coefficient of a moderator, comprising the following steps: A monitoring model for the moderator temperature coefficient is pre-established. This monitoring model is used to characterize the correspondence between reactor operating parameters and the lower limit of the moderator temperature coefficient. Collect online monitoring parameters during reactor operation, including at least the average core temperature, control rod insertion depth, and core flow rate; The online monitoring parameters are input into the supervision model to determine the risk status of the moderator temperature coefficient corresponding to the current operating condition, and to determine whether there is a risk of the moderator temperature coefficient exceeding the preset safety limit. When it is determined that there is a risk that the moderator temperature coefficient may exceed the preset safety limit, an early warning message will be output and / or the reactor will be controlled to adjust to a safe operating state.

[0012] In the method for monitoring the lower limit of the temperature coefficient of a moderator according to the present invention, the step of establishing a monitoring model for the temperature coefficient of a moderator includes: The maximum negative value of the moderator temperature coefficient of the target core under preset boundary conditions is calculated. The preset boundary conditions include the maximum value of the average core temperature allowed by the operating technical specifications, the minimum core flow rate, the maximum power level, the maximum control rod insertion depth, and the critical boron concentration boundary condition. The maximum negative value of the moderator temperature coefficient is the moderator temperature coefficient corresponding to the end-of-life condition when the core outlet temperature reaches the saturation temperature. The safety margin is determined based on the difference between the most negative value of the temperature coefficient of the moderator and the preset safety limit. Using the safety limit margin reaching a preset limit margin threshold as the search target, the corresponding single-parameter critical value, two-parameter critical combination, and three-parameter critical combination are determined; A primary supervision factor is constructed based on the single-parameter critical value, a two-dimensional decision factor is constructed based on the two-parameter critical combination, and a three-dimensional decision factor is constructed based on the three-parameter critical combination. The moderator temperature coefficient monitoring model is established based on the primary monitoring factor, the two-dimensional decision factor, and the three-dimensional decision factor.

[0013] In the method for monitoring the lower limit of the temperature coefficient of a moderator according to the present invention, determining the critical value of a single parameter includes: When the safety limit margin is greater than or equal to the preset limit margin threshold, the maximum value of the average core temperature, the minimum value of the core flow rate, the maximum value of the power level, and the maximum value of the control rod insertion depth under the preset boundary conditions are determined as the primary monitoring factor. When the safety limit margin is less than the preset limit margin threshold, a parameter critical value corresponding to making the safety limit margin equal to the preset limit margin threshold is determined, and the parameter critical value is determined as the primary supervision factor.

[0014] In the method for monitoring the lower limit of the temperature coefficient of a moderator according to the present invention, determining the parameter critical value corresponding to the preset limit margin threshold to make the safety limit margin equal to the preset limit margin threshold, and determining the parameter critical value as the primary monitoring factor includes: While keeping the other operating parameters fixed at the preset boundary conditions, the core average temperature, core flow rate, and control rod insertion depth were adjusted respectively. Calculate the most negative temperature coefficient of the moderator for each adjusted operating condition; The critical values ​​for core average temperature, core flow rate, and control rod insertion depth are determined when the difference between the most negative value of the corresponding moderator temperature coefficient and the preset safety limit reaches the preset limit margin threshold. The core average temperature critical value, the core flow rate critical value, and the control rod insertion depth critical value are determined as the primary monitoring factors.

[0015] In the method for monitoring the lower limit of the temperature coefficient of a moderator according to the present invention, determining the critical combination of two parameters includes: Obtain the primary supervision factor; One parameter of the core average temperature, control rod insertion depth and core flow rate is used as a fixed parameter, and the other two parameters are used as search parameters to construct a two-dimensional parameter space. Within each two-dimensional parameter space, a boundary search interval is determined based on the primary supervision factor. Within each boundary search interval, multiple parameter combinations are searched to make the safety limit margin reach a preset limit margin threshold. A two-dimensional critical boundary curve for the corresponding two-dimensional parameter space is formed based on the multiple parameter combinations. The two-dimensional critical boundary curve is determined as the two-dimensional decision factor.

[0016] In the method for monitoring the lower limit of the temperature coefficient of a moderator according to the present invention, determining the critical combination of the three parameters includes: Obtain the two-dimensional decision factor; Based on the two-dimensional critical boundary curve corresponding to the two-dimensional decision factor, a boundary search region is constructed in the three-dimensional parameter space consisting of the core average temperature, control rod insertion depth, and core flow rate. Within the boundary search area, the search determines multiple three-parameter combinations that cause the safety limit margin to reach a preset limit margin threshold. A three-dimensional critical boundary surface is constructed based on the combination of the multiple three parameters; The three-dimensional critical boundary surface is determined as the three-dimensional decision factor.

[0017] In the method for monitoring the lower limit of the temperature coefficient of a moderator according to the present invention, determining the risk status of the temperature coefficient of the moderator corresponding to the current operating condition includes: The average core temperature, control rod insertion depth, and core flow rate corresponding to the current operating conditions of the reactor are compared with the primary monitoring factor. When any operating parameter exceeds the corresponding primary monitoring factor, the two-dimensional judgment factor is invoked to perform a combined risk judgment. When the two-dimensional determination factor determines that there is a risk of the lower limit of the moderator temperature coefficient exceeding the limit, the three-dimensional determination factor is called to perform a three-dimensional combined risk determination. Specifically, when the combination of operating parameters formed by the core average temperature, control rod insertion depth, and core flow exceeds the three-dimensional critical boundary, it is determined that the current operating condition has a risk state of the moderator temperature coefficient exceeding the preset safety limit.

[0018] In the method for monitoring the lower limit of the temperature coefficient of a moderator described in this invention, the step of calling a two-dimensional decision factor to perform combined risk assessment includes: Determine the target operating parameters that exceed the corresponding primary monitoring factor; Obtain two additional operating parameters besides the target operating parameters; Determine whether the two-dimensional parameter combination formed by the other two operating parameters is located within the safe area defined by the two-dimensional critical boundary curve corresponding to the two-dimensional decision factor. When the other two operating parameters are within the safe range, it is determined that there is no risk of exceeding the lower limit of the temperature coefficient of the moderator in the current operating condition; When at least one operating parameter is outside the safe zone, the three-dimensional decision factor is invoked to perform a three-dimensional combined risk assessment.

[0019] The present invention also provides a device for monitoring the lower limit of the temperature coefficient of a moderator, comprising: The parameter acquisition module is used to acquire online monitoring parameters during reactor operation. The supervisory model module is used to store the supervisory model of the moderator temperature coefficient; The risk assessment module is used to input the online monitoring parameters into the supervision model and determine the risk status of the moderator temperature coefficient corresponding to the current operating condition. The early warning module is used to output early warning information and / or generate control commands when it is determined that there is a risk that the temperature coefficient of the moderator will exceed the preset safety limit.

[0020] The present invention also provides a storage medium storing a computer program, which, when executed by a processor, causes the processor to process the steps of the above-described method for monitoring the lower limit of the temperature coefficient of a moderator.

[0021] The method, terminal, and storage medium for monitoring the lower limit of the moderator temperature coefficient according to the present invention have the following beneficial effects: The present invention establishes a monitoring model in advance to characterize the correspondence between reactor operating parameters and the lower limit of the moderator temperature coefficient; collects online monitoring parameters during reactor operation, including at least the average core temperature, control rod insertion depth, and core flow rate; inputs the online monitoring parameters into the monitoring model to determine the risk status of the moderator temperature coefficient corresponding to the current operating condition, and judges whether there is a risk of the moderator temperature coefficient exceeding the preset safety limit; when a risk is determined, outputs early warning information and / or controls the reactor to adjust to a safe operating state; thus, there is no need to perform moderator temperature coefficient measurement tests during operation, nor is it necessary to change the reactor operating state through cooling, rod adjustment, or power disturbance. Online monitoring, early warning, and proactive intervention of the lower limit risk of the moderator temperature coefficient can be achieved solely using the existing online monitoring parameters of the reactor, timely detection of potential over-limit risks and guidance for operational adjustments, thereby improving the safety margin management level and reliability of safe operation during reactor operation and reducing the impact on normal unit operation. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a flowchart illustrating the method for monitoring the lower limit of the temperature coefficient of a moderator provided in an embodiment of the present invention. Figure 2 This is a flowchart illustrating the process of establishing a monitoring model for the temperature coefficient of a moderator provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the principle of the device for monitoring the lower limit of the temperature coefficient of the moderator provided in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] refer to Figure 1 This is a schematic flowchart of an optional embodiment of the moderator temperature coefficient lower limit monitoring method provided by the present invention. This method does not require invasive operations such as reactor cooling or rod adjustment. It only compares several simple core monitoring parameters with the moderator temperature coefficient monitoring model to infer the actual changes in the lower limit of the moderator temperature coefficient, thereby achieving online monitoring and management of the lower limit of the moderator temperature coefficient.

[0025] Specifically, such as Figure 1 As shown, the method for monitoring the lower limit of the temperature coefficient of a moderator includes the following steps: Step S101: Establish a monitoring model for the moderator temperature coefficient in advance. The monitoring model is used to characterize the correspondence between reactor operating parameters and the risk state of the lower limit value of the moderator temperature coefficient.

[0026] In this step, the monitoring model is preferably established in advance during the refueling design phase. The monitoring model can be a database of the most negative envelope values ​​of the moderator temperature coefficient of the target core within a preset monitoring range, used to pre-convert the complex three-dimensional physical calculations during operation into operational parameter judgment boundaries that can be quickly compared.

[0027] It should be noted that the inventors of this invention, through physical calculations, discovered and summarized the following key physical laws: when the boron concentration decreases, the moderator temperature coefficient tends to be more negative; when the core flow rate decreases, the moderator temperature coefficient tends to be more negative; when the power increases, the moderator temperature coefficient tends to be more negative; when the control rod insertion depth increases, the moderator temperature coefficient tends to be more negative; when the average core temperature increases, the moderator temperature coefficient tends to be more negative; when burnup deepens, the moderator temperature coefficient tends to be more negative.

[0028] Based on the above principles, for parameters with clearly defined limits in the operational technical specifications, during the establishment phase of the monitoring model, values ​​that lead to a more negative moderator temperature coefficient can be prioritized to reduce the workload of sensitivity analysis. For example, the power level can be set to full power. Furthermore, due to the interaction between burnup and boron concentration—that is, the deeper the burnup, the lower the boron concentration, and the moderator temperature coefficient tends to become more negative as burnup increases—the moderator temperature coefficient is more likely to approach or exceed its lower limit near the end of its service life. Therefore, in an optional embodiment, the focus can be on monitoring the impact of the current core's deviation from design conditions on the end-of-life moderator temperature coefficient, where the end-of-life moderator temperature coefficient can consider the limiting state where the critical boron concentration is zero. Based on this, the sensitivity analysis of this embodiment focuses on the impact of three parameters: core flow rate, control rod insertion depth, and core mean temperature.

[0029] refer to Figure 2 The establishment of the moderator temperature coefficient monitoring model may include the following sub-steps: Sub-step S1011: Calculate the most negative value of the moderator temperature coefficient of the target core under the preset boundary conditions, and determine the safety limit margin based on the difference between it and the preset safety limit.

[0030] Specifically, the maximum average temperature T of the reactor core is calculated under the operating technical specifications. max Minimum core flow rate D min Maximum power level P max Maximum insertion depth of the control rod C max And under the critical boron concentration boundary condition at the end of the reactor's lifespan, assuming a core accident occurs and the core outlet temperature reaches saturation, obtain the most negative value of the moderator temperature coefficient (MTC) corresponding to the preset boundary condition. min,s .

[0031] Based on the most negative value of the moderator temperature coefficient (MTC) min,s Compared with the preset safety limit MTC limit The difference between them determines the safety limit margin Δ MTC,l ,in: .

[0032] It should be noted that the preset safety limit value described in this embodiment of the invention is the lower limit value of the moderator temperature coefficient assumed in the safety analysis report. The preset limit margin threshold can be determined based on engineering experience and safety margin requirements, and it can be zero or a conservative margin value greater than zero.

[0033] Sub-step S1012: Taking the safety limit margin reaching the preset limit margin threshold as the search target, determine the single parameter critical value, and construct the primary supervision factor based on the single parameter critical value.

[0034] Specifically, it is determined whether the safety limit margin obtained in sub-step S1011 is greater than or equal to the preset limit margin threshold. If the safety limit margin is greater than or equal to the preset limit margin threshold, it indicates that the moderator temperature coefficient has not exceeded the preset safety limit under the condition that all operating parameters are taken as preset boundary conditions. In this case, the boundary values ​​of the operating parameters corresponding to the preset boundary conditions can be used as primary monitoring factors. That is, the maximum value of the core average temperature, the minimum value of the core flow rate, the maximum value of the power level, and the maximum value of the control rod insertion depth are determined as the primary monitoring factors.

[0035] If the safety margin is less than the preset safety margin threshold, it indicates that the moderator temperature coefficient is at risk of approaching or exceeding the preset safety limit under the preset boundary condition. In this case, a critical search is performed on a single operating parameter. Specifically, while keeping the other parameters fixed at the preset boundary condition, the core average temperature T, core flow rate D, and control rod insertion depth C are adjusted respectively. The most negative value of the moderator temperature coefficient corresponding to each adjusted condition is calculated, and the critical values ​​of core average temperature T1, core flow rate D1, and control rod insertion depth C1 corresponding to the safety margin reaching the preset safety margin threshold are determined. The critical values ​​of core average temperature T1, core flow rate D1, and control rod insertion depth C1 are determined as the primary monitoring factors.

[0036] For example, while maintaining a power level of P max Under the given conditions, the single-parameter critical condition corresponding to the primary supervision factor can be expressed as follows: The first row represents the single-parameter critical condition obtained using the core average temperature as the search parameter; the second row represents the single-parameter critical condition obtained using the core flow rate as the search parameter; and the third row represents the single-parameter critical condition obtained using the control rod insertion depth as the search parameter. The primary monitoring factor is used for preliminary risk assessment during the operational phase. When any online monitoring parameter exceeds the corresponding primary monitoring factor, subsequent combined risk assessment is initiated.

[0037] Sub-step S1013: Using the safety limit margin reaching the preset limit margin threshold as the search target, determine the two-parameter critical combination, and construct a two-dimensional judgment factor based on the two-parameter critical combination.

[0038] It should be noted that after the primary monitoring factor is determined in sub-step S1012, when a certain operating parameter exceeds the corresponding primary monitoring factor, it does not necessarily mean that the temperature coefficient of the moderator has exceeded the preset safety limit; if the other operating parameters still have sufficient margin, the current operating condition may still be in a safe state. Therefore, this embodiment of the invention further establishes a two-dimensional judgment factor to achieve a refined judgment of the combined effect of the two operating parameters.

[0039] Specifically, the primary monitoring factor is obtained, and one of the following parameters—core average temperature T, core flow rate D, and control rod insertion depth C—is used as a fixed parameter, while the remaining two parameters are used as search parameters to construct a corresponding two-dimensional parameter space. The two-dimensional parameter space may include the TC parameter plane, the TD parameter plane, and the DC parameter plane.

[0040] Within each two-dimensional parameter space, a boundary search interval is determined based on the primary supervision factor. Within each boundary search interval, multiple parameter combinations are searched to ensure that the safety limit margin reaches a preset limit margin threshold. A two-dimensional critical boundary curve is formed based on the multiple parameter combinations, and this two-dimensional critical boundary curve is determined as a two-dimensional decision factor.

[0041] In one embodiment, the search for the two-dimensional critical boundary curve can be performed as follows: The search interval is determined by two single-parameter critical conditions in the corresponding two-dimensional parameter plane.

[0042] For example, taking a fixed core flow rate D as an example, when searching within the TC parameter plane, step S1012 has already obtained the critical value T1 for the core average temperature and the critical value C1 for the control rod insertion depth. At this point, it can be determined that: First endpoint condition: T=T1, C=C max ; Second endpoint condition: T=T max C=C1; Where D remains a fixed value, and the power level remains at P. max .

[0043] Within the search interval defined by the two endpoint conditions mentioned above, the combination of T and C is changed, and the safety margin Δ corresponding to each combination condition is calculated. MTC,l The combination of multiple parameters that satisfy the safety limit margin reaching the preset limit margin threshold is denoted as (T). i C i ), where i is a positive integer.

[0044] A two-dimensional critical boundary curve in the TC parameter plane is formed based on the multiple parameter combinations (Ti, Ci). It should be noted that the two-dimensional critical boundary curve is not formed by directly connecting the two endpoint conditions mentioned above, but rather is the trajectory of parameter combinations obtained through physical calculation within the search interval, where the safety limit margin is equal to the preset limit margin threshold.

[0045] Optionally, the search is performed using an adaptive grid search method. Specifically, calculations can first be performed within the search interval using a first grid spacing to determine the region where the safety limit margin is close to the preset limit margin threshold; then, a more intensive search is performed within this region using a second grid spacing, wherein the second grid spacing is smaller than the first grid spacing.

[0046] Furthermore, when the safety limit margins corresponding to adjacent grid nodes are located on both sides of the preset limit margin threshold, or when the difference between them and the preset limit margin threshold is less than a preset range, local interpolation calculations are performed on the adjacent grid nodes to determine the two-dimensional critical boundary curve.

[0047] The two-dimensional critical boundary curve is used to divide the corresponding two-dimensional parameter space into safe and risk regions, and is stored in the supervision model as the corresponding two-dimensional decision factor.

[0048] Sub-step S1014: Taking the safety limit margin reaching the preset limit margin threshold as the search target, determine the three-parameter critical combination, and construct a three-dimensional judgment factor based on the three-parameter critical combination.

[0049] Specifically, the two-dimensional decision factor determined in sub-step S1013 is obtained, and based on the two-dimensional critical boundary curve corresponding to the two-dimensional decision factor, a boundary search region is constructed in the three-dimensional parameter space composed of the core average temperature T, core flow rate D, and control rod insertion depth C.

[0050] Within the boundary search area, multiple three-parameter critical combinations are searched that result in the safety limit margin reaching the preset limit margin threshold. A three-dimensional critical boundary surface is constructed based on these multiple three-parameter critical combinations. The three-dimensional critical boundary surface is used to divide the three-dimensional parameter space into a safe region and a risk region, and serves as the three-dimensional decision factor.

[0051] Optionally, the three-parameter critical combination can be obtained through interpolation search. Specifically, the parameter combination on the two-dimensional critical boundary curve can be used as the initial boundary point of the three-dimensional search, and interpolation search can be performed within a preset range of the third parameter to determine the three-parameter critical combination that satisfies the safety limit margin reaching the preset limit margin threshold.

[0052] For example, taking the two-dimensional critical combination (D2, C2) obtained by searching in the DC parameter plane formed by the core flow rate D and the control rod insertion depth C in sub-step S1013 as an example, when the core average temperature T is taken as the maximum value of the core average temperature T max At that time, a boundary reference point (T) can be formed in the three-dimensional parameter space. max (D2, C2).

[0053] Near this boundary reference point, if the core flow rate D=D2 remains constant and the control rod insertion depth C is increased so that C>C2, the moderator temperature coefficient tends to be more negative, and the safety margin may be lower than the preset limit margin threshold. In this case, the core average temperature T can be less than T0. max And the control rod insertion depth C is located between C1 and C max Interpolation search is performed within the range between to obtain a three-parameter critical combination (T) that satisfies the safety limit margin reaching the preset limit margin threshold. i D2, C i ), where i is a positive integer.

[0054] Based on multiple three-parameter critical combinations (T) i D i C i Interpolation or fitting is performed to form the three-dimensional critical boundary surface, and the three-dimensional critical boundary surface is stored as a three-dimensional decision factor in the supervised model.

[0055] Sub-step S1015: Establish the moderator temperature coefficient monitoring model based on the primary monitoring factor, the two-dimensional decision factor, and the three-dimensional decision factor.

[0056] Specifically, a monitoring model database is established; the primary monitoring factor, the two-dimensional judgment factor, and the three-dimensional judgment factor are stored in a hierarchical manner; the monitoring model is called in sequence according to single-parameter judgment, two-parameter judgment, and three-parameter judgment to determine the risk status of the moderator temperature coefficient corresponding to the current operating condition.

[0057] Optionally, the supervised model database is organized using a hierarchical node structure, as illustrated below: Through steps S1011 to S1015, this embodiment of the invention pre-establishes a monitoring model for the moderator temperature coefficient. Compared with directly performing three-dimensional physical calculations of the moderator temperature coefficient during the operation phase, this embodiment of the invention pre-determines single-parameter critical values, two-parameter critical combinations, and three-parameter critical combinations through offline fuel consumption calculations, sensitivity analysis, and boundary search, and constructs a corresponding monitoring model database. This transforms the complex problem of determining the lower limit of the moderator temperature coefficient into a comparison problem between operating parameters and preset judgment boundaries.

[0058] Furthermore, in this embodiment of the invention, a monitoring model is established by hierarchically associating primary monitoring factors, two-dimensional judgment factors, and three-dimensional judgment factors. This allows for the risk determination of the lower limit of the moderator temperature coefficient without re-performing complex core physics calculations during the operation phase, thereby reducing the online computing load and improving the real-time performance and engineering feasibility of risk monitoring.

[0059] Furthermore, by establishing two-dimensional critical boundary curves and three-dimensional critical boundary surfaces, the embodiments of the present invention can fully consider the coupling effect between the core average temperature, core flow rate, and control rod insertion depth. Compared with the method of monitoring only using single parameter limits, this can improve the accuracy of risk assessment of the lower limit of the moderator temperature coefficient and reduce false alarms and missed alarms.

[0060] Step S102: Collect online monitoring parameters during reactor operation. The online monitoring parameters include at least the average core temperature, control rod insertion depth, and core flow rate.

[0061] In this step, the online monitoring parameters correspond to the monitoring parameters used when establishing the monitoring model in step S101, wherein the average core temperature corresponds to the temperature parameter T in the monitoring model, the core flow rate corresponds to the flow rate parameter D in the monitoring model, and the control rod insertion depth corresponds to the control rod parameter C in the monitoring model.

[0062] The above-mentioned online monitoring parameters are all existing operating parameters that can be directly monitored and obtained during reactor operation. There is no need to install additional dedicated measuring equipment, nor is it necessary to introduce additional disturbances to the reactor core through cooling, rod adjustment, power disturbance, or other means.

[0063] Therefore, the embodiments of the present invention can acquire parameter information for risk monitoring of the lower limit of the temperature coefficient of the moderator in real time without affecting the normal operation of the unit, providing a data basis for subsequent risk assessment.

[0064] Step S103: Input the online monitoring parameters into the supervision model to determine the risk status of the moderator temperature coefficient corresponding to the current operating condition, and determine whether there is a risk of the moderator temperature coefficient exceeding the preset safety limit.

[0065] Specifically, determining the risk status of the moderator temperature coefficient corresponding to the current operating condition includes the following process: First, a preliminary risk assessment is performed. The core mean temperature T, core flow rate D, and control rod insertion depth C corresponding to the current reactor operating condition are compared with the primary monitoring factors. If any of the following conditions are met, the current operating condition is determined to have a preliminary risk, and a combined risk assessment is performed using two-dimensional judgment factors: the core mean temperature T is greater than the core mean temperature critical value in the primary monitoring factors; the core flow rate D is less than the core flow rate critical value in the primary monitoring factors; and the control rod insertion depth C is greater than the control rod insertion depth critical value in the primary monitoring factors.

[0066] Secondly, a two-dimensional combined risk assessment is performed. The target operating parameter exceeding the corresponding primary monitoring factor is determined, and the two-dimensional assessment factor corresponding to the target operating parameter is invoked. Two other operating parameters besides the target operating parameter are obtained, and it is determined whether the two-dimensional parameter combination formed by these two other operating parameters is located within the safe region defined by the corresponding two-dimensional critical boundary curve. When the two-dimensional parameter combination is within the safe region, it is determined that there is no risk of exceeding the lower limit of the moderator temperature coefficient under the current operating condition, and no three-dimensional combined risk assessment is required. When the two-dimensional parameter combination is outside the safe region, the three-dimensional assessment factor is invoked to perform a three-dimensional combined risk assessment.

[0067] Finally, a three-dimensional risk assessment is performed. The three-dimensional operating parameter combination formed by the core average temperature T, core flow rate D, and control rod insertion depth C is compared with the three-dimensional critical boundary surface. When the three-dimensional operating parameter combination is within the safe area defined by the three-dimensional critical boundary surface, it is determined that there is no risk of the moderator temperature coefficient exceeding the lower limit of the current operating condition; when the three-dimensional operating parameter combination is within the risk area defined by the three-dimensional critical boundary surface, it is determined that there is a risk of the moderator temperature coefficient exceeding the preset safety limit of the current operating condition.

[0068] For example, suppose the primary monitoring factors include the core mean temperature critical value T1, the core flow rate critical value D1, and the control rod insertion depth critical value C1. The online monitoring parameters corresponding to the current operating condition are the core mean temperature T0, the core flow rate D0, and the control rod insertion depth C0.

[0069] When T0 > T1, D0 > D1, and C0 < C1, it indicates that the core average temperature exceeds its corresponding primary monitoring factor, but the core flow rate and control rod insertion depth have not yet individually exceeded their respective primary monitoring factors. Therefore, the core average temperature is determined as the target operating parameter, and the two-dimensional decision factor corresponding to the core average temperature is invoked.

[0070] Specifically, the current core flow rate D0 and control rod insertion depth C0 are obtained to form a two-dimensional parameter combination (D0, C0), and it is determined whether the two-dimensional parameter combination is located within the safe region defined by the two-dimensional critical boundary curve corresponding to the DC parameter plane.

[0071] If (D0, C0) is located within the safe area, it means that although the core average temperature T0 exceeds the core average temperature critical value T1, the core flow rate D0 and the control rod insertion depth C0 still have sufficient margin, and there is no risk of exceeding the lower limit of the moderator temperature coefficient under the current operating conditions.

[0072] If (D0, C0) is located within the risk area defined by the two-dimensional critical boundary curve, then the three-dimensional judgment factor is further invoked to compare the three-dimensional operating parameter combination (T0, D0, C0) corresponding to the current operating condition with the three-dimensional critical boundary surface.

[0073] When (T0, D0, C0) is within the safe area defined by the three-dimensional critical boundary surface, it is determined that there is no risk of the lower limit of the moderator temperature coefficient exceeding the limit under the current operating condition; when (T0, D0, C0) is within the risk area defined by the three-dimensional critical boundary surface, it is determined that there is a risk of the moderator temperature coefficient exceeding the preset safety limit under the current operating condition.

[0074] Through the aforementioned graded risk assessment process, this embodiment of the invention first utilizes primary monitoring factors for rapid screening, only invoking two-dimensional judgment factors when operating parameters exceed the corresponding primary monitoring factors; and only when two-dimensional combined risk assessment cannot eliminate the risk of exceeding limits, further invoking three-dimensional judgment factors for refined analysis. Therefore, compared to directly using a three-dimensional boundary model to assess all operating conditions, this embodiment of the invention reduces the number of calls to three-dimensional judgment factors, lowers the computational complexity in the online monitoring process, and improves the real-time performance and response efficiency of risk monitoring. Furthermore, this embodiment of the invention considers the coupling effect between core average temperature, core flow rate, and control rod status parameters at each level through two-dimensional and three-dimensional judgment factors, avoiding false alarms caused by relying solely on single parameter limits, thereby improving the accuracy and reliability of risk assessment for the lower limit of the moderator temperature coefficient.

[0075] Step S104: When it is determined that there is a risk that the moderator temperature coefficient will exceed the preset safety limit, output early warning information and / or control the reactor to adjust to a safe operating state.

[0076] Specifically, when step S103 ultimately determines that there is a risk of the current core state exceeding the lower limit of the moderator temperature coefficient, an early warning message is output. The early warning message may include at least one of the following: risk warning information, operating parameters corresponding to the risk of exceeding the limit, risk determination result, and suggested adjustment measures.

[0077] Optionally, the proposed adjustments may include adjusting at least one of the core average temperature, core flow rate, and control rod status parameters to a safe range defined by the monitoring model, and / or controlling the unit to operate at reduced power.

[0078] In one embodiment, the warning information can be used to prompt operators to perform operational adjustment operations; in another embodiment, control commands can also be generated to enable the reactor control system to adjust the current operating conditions to a safe operating state.

[0079] Through the above methods, the embodiments of the present invention can provide timely risk warnings and adjustment basis when there is a risk of the temperature coefficient of the moderator exceeding the preset safety limit, so that operators or control systems can take corresponding measures to reduce the risk of the lower limit of the temperature coefficient of the moderator exceeding the limit.

[0080] This invention establishes a monitoring model for the most negative value of the moderator temperature coefficient within a preset monitoring range through multi-parameter sensitivity analysis in the early stage. It transforms complex real-time three-dimensional physical calculations into simple comparison of operating parameter thresholds, realizing non-intrusive online monitoring of the safety analysis assumption limits. It can respond quickly without shutting down the reactor or adjusting operating parameters. This avoids safety hazards such as core oscillations and unnecessary power generation losses caused by traditional measurement methods, and reduces the dependence on high-performance computing resources. It enables nuclear power units to continuously confirm that the lower limit of the moderator temperature coefficient will not exceed the limit of the safety analysis assumption under any operating conditions, which can significantly improve the economic efficiency of operation and the real-time performance and reliability of safety monitoring.

[0081] The following describes the device for monitoring the lower limit of the temperature coefficient of a moderator provided in an embodiment of the present invention. For example... Figure 3 As shown, the device includes: a parameter acquisition module 310, a supervision model module 320, a risk determination module 330, and an early warning module 340.

[0082] The reactor features a parameter acquisition module for acquiring online monitoring parameters during reactor operation, including at least the core mean temperature, control rod insertion depth, and core flow rate. A monitoring model module stores a moderator temperature coefficient monitoring model, which includes the aforementioned primary monitoring factor, two-dimensional decision factor, and three-dimensional decision factor. A risk assessment module inputs the online monitoring parameters into the monitoring model and determines the moderator temperature coefficient risk status corresponding to the current operating condition. An early warning module outputs early warning information and / or generates control commands when a risk of the moderator temperature coefficient exceeding a preset safety limit is detected.

[0083] The device for monitoring the lower limit of the temperature coefficient of a moderator provided in this embodiment of the invention corresponds to the aforementioned method for monitoring the lower limit of the temperature coefficient of a moderator. The specific functions of each module can be found in the relevant description in the method section, and will not be repeated here.

[0084] The present invention also provides a storage medium storing a computer program, which, when executed by a processor, causes the processor to process the steps of the method for monitoring the lower limit of the temperature coefficient of a moderator disclosed in the embodiments of the present invention.

[0085] The moderator temperature coefficient lower limit monitoring method of this invention establishes a monitoring model for the most negative value of the moderator temperature coefficient within a preset monitoring range through multi-parameter sensitivity analysis in the early stage. This transforms complex real-time three-dimensional physical calculations into simple comparison of operating parameter thresholds, achieving non-intrusive online monitoring of the safety analysis assumption limits. This method allows for rapid response without reactor shutdown or adjustment of operating parameters, avoiding safety hazards such as core xenon oscillations or even accidental reactor trips caused by traditional measurement methods, and also avoiding unnecessary power generation losses caused by reduced power operation for measurement experiments.

[0086] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0087] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0088] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0089] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They do not limit the scope of protection of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for monitoring the lower limit of the temperature coefficient of a moderator, characterized in that, Includes the following steps: A monitoring model for the moderator temperature coefficient is pre-established. This monitoring model is used to characterize the correspondence between reactor operating parameters and the lower limit of the moderator temperature coefficient. Collect online monitoring parameters during reactor operation, including at least the average core temperature, control rod insertion depth, and core flow rate; The online monitoring parameters are input into the supervision model to determine the risk status of the moderator temperature coefficient corresponding to the current operating condition, and to determine whether there is a risk of the moderator temperature coefficient exceeding the preset safety limit. When it is determined that there is a risk that the moderator temperature coefficient may exceed the preset safety limit, an early warning message will be output and / or the reactor will be controlled to adjust to a safe operating state.

2. The method for monitoring the lower limit of the temperature coefficient of a moderator according to claim 1, characterized in that, The establishment of the temperature coefficient monitoring model for the moderator includes: The maximum negative value of the moderator temperature coefficient of the target core under preset boundary conditions is calculated. The preset boundary conditions include the maximum value of the average core temperature allowed by the operating technical specifications, the minimum core flow rate, the maximum power level, the maximum control rod insertion depth, and the critical boron concentration boundary condition. The maximum negative value of the moderator temperature coefficient is the moderator temperature coefficient corresponding to the end-of-life condition when the core outlet temperature reaches the saturation temperature. The safety margin is determined based on the difference between the most negative value of the temperature coefficient of the moderator and the preset safety limit. Using the safety limit margin reaching a preset limit margin threshold as the search target, the corresponding single-parameter critical value, two-parameter critical combination, and three-parameter critical combination are determined; A primary supervision factor is constructed based on the single-parameter critical value, a two-dimensional decision factor is constructed based on the two-parameter critical combination, and a three-dimensional decision factor is constructed based on the three-parameter critical combination. The moderator temperature coefficient monitoring model is established based on the primary monitoring factor, the two-dimensional decision factor, and the three-dimensional decision factor.

3. The method for monitoring the lower limit of the temperature coefficient of a moderator according to claim 2, characterized in that, The determination of the single-parameter critical value includes: When the safety limit margin is greater than or equal to the preset limit margin threshold, the maximum value of the average core temperature, the minimum value of the core flow rate, the maximum value of the power level, and the maximum value of the control rod insertion depth under the preset boundary conditions are determined as the primary monitoring factor. When the safety limit margin is less than the preset limit margin threshold, a parameter critical value is determined to make the safety limit margin equal to the preset limit margin threshold, and the parameter critical value is determined as the primary supervision factor.

4. The method for monitoring the lower limit of the temperature coefficient of a moderator according to claim 3, characterized in that, Determining the parameter critical values ​​that make the safety limit margin equal to the preset limit margin threshold, and defining the parameter critical values ​​as the primary supervision factors, includes: While keeping the other operating parameters fixed at the preset boundary conditions, the core average temperature, core flow rate, and control rod insertion depth were adjusted respectively. Calculate the most negative temperature coefficient of the moderator for each adjusted operating condition; Determine the critical values ​​for core average temperature, core flow rate, and control rod insertion depth when the difference between the most negative value of the corresponding moderator temperature coefficient and the preset safety limit reaches the preset limit margin threshold. The core average temperature critical value, the core flow rate critical value, and the control rod insertion depth critical value are determined as the primary monitoring factors.

5. The method for monitoring the lower limit of the temperature coefficient of a moderator according to claim 2, characterized in that, Determining the critical combination of two parameters includes: Obtain the primary supervision factor; One parameter of the core average temperature, control rod insertion depth and core flow rate is used as a fixed parameter, and the other two parameters are used as search parameters to construct a two-dimensional parameter space. Within each two-dimensional parameter space, a boundary search interval is determined based on the primary supervision factor. Within each boundary search interval, multiple parameter combinations are searched to make the safety limit margin reach a preset limit margin threshold. A two-dimensional critical boundary curve for the corresponding two-dimensional parameter space is formed based on the multiple parameter combinations. The two-dimensional critical boundary curve is determined as the two-dimensional decision factor.

6. The method for monitoring the lower limit of the temperature coefficient of a moderator according to claim 2, characterized in that, The determination of the critical combination of the three parameters includes: Obtain the two-dimensional decision factor; Based on the two-dimensional critical boundary curve corresponding to the two-dimensional decision factor, a boundary search region is constructed in the three-dimensional parameter space consisting of the core average temperature, control rod insertion depth, and core flow rate. Within the boundary search area, the search determines multiple three-parameter combinations that cause the safety limit margin to reach a preset limit margin threshold. A three-dimensional critical boundary surface is constructed based on the combination of the multiple three parameters; The three-dimensional critical boundary surface is determined as the three-dimensional decision factor.

7. The method for monitoring the lower limit of the temperature coefficient of a moderator according to claim 2, characterized in that, The determination of the risk status of the moderator temperature coefficient corresponding to the current operating condition includes: The average core temperature, control rod insertion depth, and core flow rate corresponding to the current operating conditions of the reactor are compared with the primary monitoring factor. When any operating parameter exceeds the corresponding primary monitoring factor, the two-dimensional judgment factor is invoked to perform a combined risk judgment. When the two-dimensional determination factor determines that there is a risk of the lower limit of the moderator temperature coefficient exceeding the limit, the three-dimensional determination factor is called to perform a three-dimensional combined risk determination. Specifically, when the combination of operating parameters formed by the core average temperature, control rod insertion depth, and core flow exceeds the three-dimensional critical boundary, it is determined that the current operating condition has a risk state of the moderator temperature coefficient exceeding the preset safety limit.

8. The method for monitoring the lower limit of the temperature coefficient of a moderator according to claim 7, characterized in that, The method of using two-dimensional judgment factors to determine combined risk includes: Determine the target operating parameters that exceed the corresponding primary monitoring factor; Obtain two additional operating parameters besides the target operating parameters; Determine whether the two-dimensional parameter combination formed by the other two operating parameters is located within the safe area defined by the two-dimensional critical boundary curve corresponding to the two-dimensional decision factor. When the other two operating parameters are within the safe range, it is determined that there is no risk of exceeding the lower limit of the temperature coefficient of the moderator in the current operating condition; When at least one operating parameter is outside the safe zone, the three-dimensional decision factor is invoked to perform a three-dimensional combined risk assessment.

9. A device for monitoring the lower limit of the temperature coefficient of a moderator, characterized in that, include: The parameter acquisition module is used to acquire online monitoring parameters during reactor operation. The supervisory model module is used to store the supervisory model of the moderator temperature coefficient; The risk assessment module is used to input the online monitoring parameters into the supervision model and determine the risk status of the moderator temperature coefficient corresponding to the current operating condition. The early warning module is used to output early warning information and / or generate control commands when it is determined that there is a risk that the temperature coefficient of the moderator will exceed the preset safety limit.

10. A storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, causes the processor to perform the steps of the method for monitoring the lower limit of the temperature coefficient of a moderator as described in any one of claims 1-8.

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