A method for coupling the thermohydraulic response of a containment with the mass and energy release

Abstract

The present invention relates to a method for coupling the thermal-hydraulic response of a containment with the mass-energy release. The calculation of the mass-energy release of a high-energy pipe break is carried out using system analysis software, and the calculation of the thermal-hydraulic response of the containment is carried out using containment analysis software. The thermal-hydraulic response of the containment is coupled with the mass-energy release, and the calculation results of the two software are used as the input boundaries for each other. After multiple iterations, a more realistic simulation result is finally obtained. The present invention provides a method for nuclear power plant accident analysis, solves the problem that the calculation of some accident sequences is too conservative, avoids the addition of new mitigation measures, meets the safety requirements, and thus improves the economy of the nuclear power plant.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear power plant design, and particularly relates to a method for coupling the thermal-hydraulic response and mass-energy release of a containment. Background Art

[0002] Pressurized water reactor nuclear power plants are all equipped with a containment. The design of the containment and its related systems should ensure that the nuclear power plant achieves radioactive containment, defends against external and internal hazards, and provides biological shielding. The design characteristics of the containment include maintaining the pressure and temperature within acceptable limits. Once an accident of a high-energy pipeline rupture occurs inside the containment, due to the entry of a high-temperature and high-pressure water and steam mixture into the containment space, the pressure and temperature of the containment will rise and reach a stable state after a period of time. During this accident process, the free volume of the space inside the containment accommodates a large-scale mass and energy release inside the containment; the containment and its internal structures and the water stored inside the containment all act as heat sinks; and various heat removal systems operate, such as the containment spray system, the passive containment heat removal system, etc.

[0003] In accident analysis, usually different calculation models or calculation software are used for the mass and energy release of the rupture of the reactor coolant system or the secondary loop system and the transient analysis of the containment pressure and temperature. The analysis process includes two steps: obtaining the mass-energy release and calculating the containment pressure. Traditional design basis accident analysis separates the two steps, and conservative assumptions are taken for each step without iteration. To obtain a larger containment pressure, a larger mass-energy release is required, and the settings of parameters such as the free volume of the containment, the heat sink, and the heat removal system are all selected as the smaller values within the design range; to obtain the maximum mass-energy release, a smaller containment pressure is required, so that the break pressure difference is larger and more fluid can be ejected. At this time, the settings of parameters such as the free volume of the containment, the heat sink, and the heat removal system are all selected as the larger values within the design range.

[0004] Newly built nuclear power plants need to conduct accident analysis for design extension conditions. If conservative calculation methods are used, it may lead to the calculated containment pressure being higher than the design pressure, thereby resulting in the need for more equipment and reducing the economic efficiency of the power plant. Summary of the Invention

[0005] The object of the present invention is to provide a method for coupling the thermal-hydraulic response and mass-energy release of a containment for the thermal design of the containment of a nuclear power plant, so as to more realistically simulate the thermal-hydraulic phenomena of the high-energy system and the containment system after a high-energy pipeline rupture accident inside the containment, and give the thermal-hydraulic responses of all high-energy systems and the thermal-hydraulic response of the containment, including the changes in parameters such as temperature and pressure, and conduct a safety assessment of the thermal-hydraulic state of the nuclear power plant core and the containment.

[0006] The technical solution of the present invention is as follows: A method for coupling the thermohydraulic response and mass-energy release of a containment vessel, comprising the following steps:

[0007] (S01) Determine the accident type and calculate the initial mass-energy release;

[0008] (S02) Perform initial processing of the mass-energy release data for the initial calculation of the containment vessel's thermohydraulic response;

[0009] (S03) Perform the initial calculation of the containment vessel's thermohydraulic response;

[0010] (S04) Process the containment vessel pressure and the water temperature inside the vessel obtained from the calculation of the containment vessel's thermohydraulic response to obtain input parameters that can be used for the calculation of mass-energy release;

[0011] (S05) Use the parameters processed in step (S04) to perform iterative calculations of mass-energy release;

[0012] (S06) Process the mass-energy release calculated in step (S05) for the iterative calculation of the containment vessel's thermohydraulic response;

[0013] (S07) Use the data processed in step (S06) to perform iterative calculations of the containment vessel's thermohydraulic response;

[0014] (S08) Compare the containment vessel pressure calculated in step (S07) with the calculation result of step (S03) or step (S07) in the previous iteration, and use the convergence criterion to judge the result deviation. If the deviation does not meet the convergence criterion, return to step (S04) and continue to start iterative calculations; if the deviation meets the convergence criterion, end the calculation.

[0015] Furthermore, for the method for coupling the thermohydraulic response and mass-energy release of the containment vessel as described above, in which the calculation of mass-energy release uses a system analysis software, and the calculation of the thermohydraulic response of the containment vessel uses a containment vessel analysis software.

[0016] Furthermore, for the method for coupling the thermohydraulic response and mass-energy release of the containment vessel as described above, when calculating the initial mass-energy release in step (S01), the containment vessel pressure and the water temperature inside the vessel adopt fixed values.

[0017] Furthermore, for the method for coupling the thermohydraulic response and mass-energy release of the containment vessel as described above, the data processing in steps (S02), (S04), and (S06) includes selecting data points at a set interval and calculating the average value of the data at a set interval.

[0018] Further, in the method for coupling the containment thermal-hydraulic response and the mass-energy release as described above, the convergence criterion in step (S07) is that the deviation between the containment pressure obtained from the n-th iterative calculation and the containment pressure obtained from the initial calculation in step (S03) or the containment pressure obtained from the (n-1)-th iterative calculation is less than 10%.

[0019] The beneficial effects of the present invention are as follows: The present invention couples the containment thermal-hydraulic response and the mass-energy release, uses the calculation results of the two software as the input boundaries for each other, and finally obtains a more realistic simulation result after multiple iterations. This method realizes the parameter transfer between the containment thermal-hydraulic response analysis software and the mass-energy release analysis software, converts the parameters into the parameter forms that can be read and recognized by the software, and gives a judgment method for terminating the iteration by setting the coupling iteration convergence criterion. The present invention provides a method for accident analysis of nuclear power plants, solves the problem that the calculation of some accident sequences is too conservative, avoids adding new mitigation measures, meets the safety requirements, and thus improves the economy of nuclear power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart of the method for coupling the containment thermal-hydraulic response and the mass-energy release of the present invention;

[0021] Figure 2 It is a schematic diagram of the operation of the containment cooling system in the case of a break accident in the embodiment of the present invention;

[0022] Figure 3 It is a graph of the break mass flow rate calculated by the system analysis software in the embodiment of the present invention;

[0023] Figure 4 It is a graph of the break fluid enthalpy value calculated by the system analysis software in the embodiment of the present invention;

[0024] Figure 5 It is a graph of the gas pressure inside the containment calculated by the containment analysis software in the embodiment of the present invention;

[0025] Figure 6 It is a graph of the temperature of the water inside the containment obtained by the containment analysis software in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] The present invention is a calculation method that couples a system analysis software and a containment analysis software, that is, uses the system analysis software to calculate the mass-energy release of a high-energy pipeline break, uses the containment analysis software to calculate the thermal-hydraulic response of the containment, and conducts a more realistic simulation of the system through coupled calculations.

[0028] The method for coupling the thermal-hydraulic response and mass-energy release of the containment of the present invention includes the following steps:

[0029] (S01) Determine the accident type and calculate the initial mass-energy release. At this time, the containment pressure and the water temperature inside the containment adopt fixed values;

[0030] (S02) Conduct initial mass-energy release data processing for the initial calculation of the thermal-hydraulic response of the containment;

[0031] (S03) Conduct the initial calculation of the thermal-hydraulic response of the containment;

[0032] (S04) Process the containment pressure and the water temperature inside the containment obtained from the thermal-hydraulic response calculation to obtain input parameters that can be used for mass-energy release calculation;

[0033] (S05) Use the parameters processed in step (S04) to conduct iterative calculations of mass-energy release;

[0034] (S06) Process the mass-energy release calculated in step (S05) for iterative calculation of the thermal-hydraulic response of the containment;

[0035] (S07) Use the data in step (S06) to conduct iterative calculations of the thermal-hydraulic response of the containment;

[0036] (S08) Compare the containment pressure calculated in step (S07) with the calculation result in step (S03) or the calculation result in step (S07) of the previous iteration, and use the convergence criterion to judge the result deviation. If the deviation does not meet the convergence criterion, return to step (S04) and continue to start iterative calculations; if the deviation meets the convergence criterion, end the calculation.

[0037] (S09) End.

[0038] In the process of processing the parameters in steps (S02), (S04), and (S06), operations such as parameter quantity and time stage division should be carried out for specific analysis software. For example, methods such as selecting data points at specific intervals and calculating the average value of data at specific intervals.

[0039] The following Figure 2 describes the method of the present invention through the specific heat export system inside the containment shown in Figure 2In the system shown, after a break 2 occurs in the high-energy system 1, the high-energy fluid enters the containment 3, and the in-containment heat sink pool 4, internal structure 5, and containment shell 6 absorb heat. Related systems such as the spray system 7 and the passive containment heat removal system 8 remove the heat inside the containment.

[0040] (1) The first calculation includes steps S01, S02, and S03. The containment pressure and the water temperature inside the containment are input into the system analysis software RELAP using fixed values to obtain the initial mass and energy release, and the data is processed. The processing method is to obtain the average value by segmentation to obtain the input data for the containment analysis. The containment analysis software COPAT uses the processed mass and energy release data to carry out the containment response analysis.

[0041] (2) Multiple iterations start from the data processing of the containment pressure and the water temperature inside the containment, including steps S04, S05, S06, and S07. The containment pressure and the water temperature inside the containment are obtained by using the method of obtaining the average value by segmentation to obtain the input data for the system analysis software. The system analysis software calculates the system response to obtain the mass and energy release after iteration, which is processed and used as the input data for the containment analysis software. The containment analysis software calculates the thermal-hydraulic response of the containment to obtain the containment pressure and the water temperature inside the containment.

[0042] (3) Compare the calculated result of the containment pressure with the result of the previous calculation to determine whether the following convergence criterion is satisfied.

[0043]

[0044] where, P n is the peak value of the containment pressure obtained from the nth iterative calculation. The first calculation is recorded as the 1st iteration, and the 1st iteration is compared with the containment pressure result obtained from the initial calculation in step (S03). When the convergence criterion is satisfied in the iterative calculation, it is considered that the mass and energy release and the thermal-hydraulic response of the containment have been matched, and the calculation result has converged.

[0045] Figures 3 - 6 is the calculation result of this embodiment. Figure 3 is the break mass flow rate calculated by the system analysis software, Figure 4 is the break fluid enthalpy value calculated by the system analysis software. Figure 5 is the gas pressure inside the containment obtained by the containment analysis software, Figure 6 is the temperature of the water inside the containment obtained by the containment analysis software. The results of the embodiment show that the pressure of the containment is lower than the design limit, meeting the safety standards and design requirements, and there is no need to set up additional cooling facilities.

[0046] For those skilled in the art, it is obvious that the structure of the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Accordingly, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims concerned.

[0047] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for coupling the thermohydraulic response of a containment and the mass-energy release, comprising the following steps: (S01) Determine the accident type, calculate the initial mass-energy release, and obtain the break mass flow rate and the break fluid enthalpy value; (S02) Conduct initial data processing of the mass-energy release, including selecting data points at a set interval and calculating the average value of the data at a set interval for the initial calculation of the thermohydraulic response of the containment; (S03) Conduct the initial calculation of the thermohydraulic response of the containment to obtain the containment pressure and the water temperature inside the containment; (S04) Conduct data processing on the containment pressure and the water temperature inside the containment obtained from the calculation of the thermohydraulic response of the containment, including selecting data points at a set interval and calculating the average value of the data at a set interval to obtain the input parameters available for the calculation of the mass-energy release; (S05) Use the parameters processed in step (S04) to conduct iterative calculations of the mass-energy release; (S06) Conduct data processing on the mass-energy release calculated in step (S05), including selecting data points at a set interval and calculating the average value of the data at a set interval for the iterative calculation of the thermohydraulic response of the containment; (S07) Use the data processed in step (S06) to conduct iterative calculations of the thermohydraulic response of the containment; (S08) Compare the containment pressure calculated in step (S07) with the calculation result in step (S03) or the calculation result of step (S07) in the previous iteration, and use the convergence criterion to judge the result deviation. If the deviation does not meet the convergence criterion, return to step (S04) and continue to start the iterative calculation; If the deviation meets the convergence criterion, end the calculation; the convergence criterion is that the deviation between the containment pressure obtained from the nth iterative calculation and the containment pressure obtained from the initial calculation in step (S03) or the containment pressure obtained from the (n - 1)th iterative calculation is less than the set value.

2. The method for coupling the thermohydraulic response of a containment and the mass-energy release according to claim 1, characterized in that, when calculating the initial mass-energy release in step (S01), the containment pressure and the water temperature inside the containment adopt fixed values.

3. The method for coupling the thermohydraulic response of a containment and the mass-energy release according to claim 1, characterized in that, the set value of the convergence criterion in step (S08) is 10%.

Images