Nuclear power plant heavy rainfall probability safety assessment method and calculation device

Abstract

A nuclear power plant heavy rainfall probability safety assessment method comprises the following steps that a heavy rainfall danger curve is established according to rainfall historical data, and factory flood peak flow and corresponding frequency under multiple rainfall intensities are calculated; according to the peak flood flow of the plant, calculating the water flooding level of the plant, and further calculating the water flooding levels of different areas in the plant; and determining the availability state of the given electrical equipment according to the flooding water level, inputting the availability state into a nuclear power plant probabilistic safety evaluation (PSA) model, and calculating to obtain the reactor core damage frequency caused by heavy rainfall. According to the method, quantitative evaluation calculation of nuclear power plant operation risks caused by heavy rainfall can be realized, and optimization of a nuclear power plant design scheme and safety management is facilitated. The invention further provides a computing device.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power, and in particular relates to a heavy rainfall probability safety assessment method and a calculation device for a nuclear power plant. Background Art

[0002] With the climate change brought about by global warming, the frequency of extreme weather such as heavy rainfall has tended to increase. At present, during the design and construction of nuclear power plants, only the prevention of water accumulation in the plant area caused by heavy rainfall from entering the nuclear island plant building is considered, and water ingress is avoided by raising the overall floor of the nuclear island plant building of the nuclear power plant. This method only carries out flood prevention according to the expected depth of water accumulation in the plant area, but cannot use the probabilistic safety assessment (PSA) tool to conduct an overall assessment of the risks brought by heavy rainfall in a quantitative manner, nor can it identify the weak links in the prevention of heavy rainfall risks, which is not conducive to improving the safety management level of nuclear power plants. Therefore, providing a probabilistic safety assessment method for heavy rainfall in nuclear power plants is of positive significance for supporting the design improvement of nuclear power plants and improving the safety management level. Summary of the invention

[0003] The purpose of the present invention is to provide a nuclear power plant heavy rainfall probability safety assessment method to quantitatively assess the nuclear power plant risk caused by heavy rainfall. The present invention also provides a calculation device.

[0004] According to an embodiment of one aspect of the present invention, a method for safety assessment of heavy rainfall probability in a nuclear power plant is provided, the method comprising the following steps:

[0005] Step a): providing historical rainfall data, and fitting and extrapolating the historical rainfall data to obtain a heavy rainfall hazard curve that characterizes the corresponding relationship between rainfall intensity and annual exceedance frequency;

[0006] Step b): providing a plurality of rainfall intensities and calculating the corresponding plant area flood peak flows, and determining the frequency corresponding to the plant area flood peak flows according to the heavy rainfall hazard curve;

[0007] Step c): Calculate the flooding level of the plant area under different rainfall intensities;

[0008] Step d): Calculating the flood flow spreading into the factory building according to the flooding water level in the factory area;

[0009] Step e): Calculating the flood levels of different areas in the plant based on the flood flow spreading into the plant;

[0010] Step f): Calculating the availability of a given electrical device according to the calculation result of step e);

[0011] Step g): establishing a heavy rainfall PSA model according to the calculation result of step f), and calculating the core damage frequency caused by heavy rainfall.

[0012] This method quantifies the risk factors caused by heavy rainfall based on meteorological data, thereby realizing a probabilistic safety assessment of the consequences of heavy rainfall. Based on this method, a comprehensive assessment of the risks caused by heavy rainfall can be made, and weak links in the design of heavy rainfall risk prevention can be identified, which is conducive to the targeted optimization of design plans and safety management.

[0013] Furthermore, in some embodiments, in the step b), the plant area peak flow calculation uses all rainfall as the peak flow.

[0014] Further, in some embodiments, in the step b), the peak flow rate Q of the plant area with an annual exceeding frequency a is a The calculation method is Q a =0.278I a F, where I a is the hourly rainfall intensity when the annual exceedance frequency is a, and F is the catchment area.

[0015] Furthermore, in some embodiments, in step c), the flooding level h of the plant area corresponding to the annual exceeding frequency a is a Solved by the broad crested weir overflow formula: Where m is the discharge coefficient and l is the overflow length of the wide crest weir.

[0016] Furthermore, in some embodiments, in step d), the calculation method of the flood flow Q0 spreading into the plant is: Q0 = C e bh0(2g(h-Δh)) 0.5 , where Ce is the contraction coefficient, b is the width of the water inlet channel, h0 is the height of the water inlet channel, g is the acceleration of gravity, Δh is the height difference between the floor of the plant and the ground of the plant, and when Q0≤0, it means that the plant is not flooded.

[0017] Furthermore, in some embodiments, in step f), the given electrical equipment includes a main transformer, a battery, an emergency diesel engine, a condensate pump, a service water pump and a circulating water pump.

[0018] Furthermore, in some embodiments, in the step g), the method for calculating the frequency of core damage caused by heavy rainfall is to substitute the availability result of the given electrical equipment calculated in the step f) into the heavy rainfall PSA model, calculate the probability of core damage caused by rainfall of different intensities, and calculate the frequency of core damage caused by heavy rainfall from the probability of core damage caused by heavy rainfall.

[0019] Furthermore, in some embodiments, the step g) also includes a step of calculating the frequency of large-scale radioactive release caused by heavy rainfall.

[0020] According to an embodiment of another aspect of the present invention, there is provided a computing device, which includes a memory and a processor, wherein the memory stores a computing program, and when the computing program is executed by the processor, the nuclear power plant heavy rainfall probabilistic safety assessment method provided in any of the aforementioned embodiments can be implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1. A schematic diagram of a flow chart of a method for safety assessment of heavy rainfall probability in a nuclear power plant in one embodiment;

[0022] Figure 2 FIG. 4 is a heavy rainfall hazard curve in one embodiment.

[0023] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0025] Mentioning "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. It should be understood by those skilled in the art that the embodiments herein can be combined with other embodiments without structural conflicts. In the description herein, terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the number, specific order or primary and secondary relationship of the described technical features. In the description herein, the meaning of "multiple" is at least two.

[0026] With climate change, the frequency of extreme weather such as heavy rainfall has an increasing trend. At present, there is no quantitative assessment method for heavy rainfall risks during the construction and operation of domestic nuclear power plants. The existing methods only consider the design to prevent water accumulation in the plant area caused by rainfall from entering the nuclear island plant: first estimate the depth of water accumulation in the nuclear power plant area under extreme rainfall conditions, and then consider a certain margin to raise the overall floor of the nuclear island plant of the nuclear power plant to prevent water accumulation in the plant area caused by rainfall from entering the nuclear island plant. The existing technical solutions do not quantitatively assess the risks of nuclear power plants caused by heavy rainfall, cannot accurately determine the weak links of nuclear power plants in preventing heavy rainfall risks, and cannot use probabilistic safety assessment (PSA) tools for analysis and optimization.

[0027] In order to solve the above problems, an embodiment of one aspect of the present invention provides a probabilistic safety assessment method for heavy rainfall in a nuclear power plant, which adopts PSA technology to quantitatively assess the heavy rainfall risk of a nuclear power plant. On the basis of this method, the safety management of the nuclear power plant can be associated with meteorological warnings, nuclear power plant flood prevention and typhoon response measures, etc., to guide the nuclear power plant to implement safety response measures more efficiently.

[0028] In one embodiment, Figure 1 As shown in the figure, the probabilistic safety assessment method for heavy rainfall in nuclear power plants includes the following steps:

[0029] Firstly, the hazard curve is obtained through heavy rainfall hazard analysis.

[0030] By collecting historical meteorological data of the plant site, we can obtain local rainfall historical data, fit the rainfall historical data and extrapolate it to obtain the following: Figure 2 The heavy rainfall hazard curve shown in the figure includes the curve 1 showing the relationship between rainfall intensity (rainfall in 1 hour) and annual exceedance frequency, and the uncertainty boundary 2 obtained based on statistical data. Figure 2 The medium uncertainty boundary 2 is the 90% uncertainty boundary.

[0031] Next, calculate the peak flow of the plant area under different rainfall intensities. Figure 2 The heavy rainfall hazard curve shown can determine the frequency corresponding to the flood peak flow in the plant area. The selection of rainfall intensity can be determined according to the gas phase disaster level classification standard, or the rainfall intensity that needs to be calculated can be determined according to the frequency of exceeding certain key years.

[0032] In the preferred embodiment, the runoff coefficient is not considered when calculating the peak flow of the plant area, and all rainfall is taken as the peak flow. Then, when the annual rainfall intensity I exceeds the frequency a, a The corresponding plant peak flow Q a =0.278I a F, where F is the confluence area.

[0033] The next step is to calculate the flooding level in the plant area under different rainfall intensities.

[0034] The flooding level h of the plant area under different rainfall intensities can be calculated using the wide crested weir overflow formula:

[0035]

[0036] Among them, m is the flow coefficient, l is the overflow length of the wide crest weir, and the flooding level h of the plant area corresponding to the exceeding frequency a in different years can be calculated according to the formula a .

[0037] The next step is to calculate the flood flow into the factory building based on the water level in the factory area.

[0038] When the depth of water accumulation in the factory area exceeds the height difference between the inside and outside of the factory building, the water accumulation in the factory area will spread into the factory building through the water inlet channel on the factory building boundary. For factories with different structures, the water inlet channel can be door gaps, vents, pipe wells, and personnel / equipment passages, etc. The calculation method for the flood flow Q0 spreading into the factory building is:

[0039] Q0=C e bh0(2g(h-Δh)) 0.5 ,

[0040] Among them, Ce is the contraction coefficient, b is the width of the water inlet channel, h0 is the height of the water inlet channel, g is the acceleration of gravity, and Δh is the height difference between the floor of the plant and the ground of the plant. When the calculation result Q0>0, it means that the plant is flooded; when Q0≤0, it means that the plant is not flooded.

[0041] In the next step, the flooding levels in various areas of the plant under different rainfall intensities were calculated.

[0042] The nuclear power plant was modeled in the general flood level calculation software, which included the structural information (area, height) of each room in the plant, the drainage facilities, the spatial distribution of the rooms in the plant, and the flood spreading path information in the plant. The flow Q0 spreading into the plant under different rainfall intensities was input into the flood level calculation model for simulation analysis to obtain the flood level of each room under the corresponding rainfall intensity.

[0043] The next step is to assess the availability of important electrical equipment under different rainfall intensities.

[0044] First, collect a list of important electrical equipment in the plant and the corresponding flood prevention information, including installation location, elevation information, and waterproof capability rating. Important electrical equipment includes main transformers, batteries, emergency diesel engines, condensate pumps, plant water pumps, and circulating water pumps, especially those installed at lower locations. Once these equipment fails due to flooding, there is a risk of causing disturbances in the operation of the power plant. Next, compare the elevation information of important electrical equipment with the flooding level in the room where the equipment is installed to evaluate the availability of each important electrical equipment under different rainfall intensities.

[0045] Finally, a heavy rainfall PSA model is established and quantitative calculations are carried out.

[0046] The core damage frequency (CDF) is used to characterize the flooding risk caused by heavy rainfall. CDF represents the number of core melts in a nuclear power plant per unit time. This data can be calculated using the PSA model.

[0047] Based on the heavy rainfall annual exceedance frequency a calculated in the previous step and the availability of the corresponding important electrical equipment, a heavy rainfall PSA model is established, and the equipment availability status is substituted into the PSA model, thereby calculating the conditional core damage probability (CCDP) caused by different rainfall intensities, and then multiplying it by the frequency of rainfall intensity to obtain the CDF under the corresponding rainfall intensity. In a preferred embodiment, the large radioactive release frequency (LRF) under different rainfall intensities can also be calculated based on the PSA model.

[0048] Through the heavy rainfall probabilistic safety assessment method for nuclear power plants provided in the above embodiment, the PSA tool can be used to quantitatively calculate the risks of nuclear power plant operation under heavy rainfall conditions, identify weak links in risk design, and support nuclear power plant design improvements and safety management optimization. At the same time, based on this method, it can be associated with meteorological warnings and nuclear power plant flood prevention and typhoon response measures to guide nuclear power plants to more efficiently implement response measures for different meteorological disasters.

[0049] According to an embodiment of another aspect of the present invention, a computing device is provided. The computing device includes a memory and a processor, and a computing program is stored in the memory. When the computing program is executed by the processor, the nuclear power plant heavy rainfall probabilistic safety assessment method provided in any of the aforementioned embodiments can be implemented. In different embodiments, the computing program may include multiple independent computing programs, such as a flooding simulation program and a nuclear power plant PSA simulation program. Different independent computing programs can automatically transmit data through a written transmission program, or data can be imported between programs through manual operation; the computing program can also use an integrated program with functions such as flooding simulation and PSA analysis, such as a special computing simulation program developed specifically for heavy rainfall scenarios, or a computing module that can implement heavy rainfall probabilistic safety assessment of nuclear power plants obtained through secondary development based on a general simulation program.

[0050] In a preferred embodiment, the process of conducting a heavy rainfall probability safety assessment for a nuclear power plant is as follows: Figure 1 as shown, and includes the following steps:

[0051] Step a): According to the historical gas phase data, the following is obtained by fitting and extrapolating: Figure 2 The heavy rainfall hazard curve 1 is shown and the 90% uncertainty boundary 2 is determined.

[0052] Step b): According to Figure 2 Determine the annual frequency of 10 -4 / year, 10 -5 Year, 10 -6 Year, 10 -7 years and 10 -8 The corresponding 1h rainfall in the year:

[0053] 10 -4The corresponding rainfall per hour is 14 cm per year. -5 The corresponding rainfall per hour is 17 cm. -6 The corresponding rainfall per hour is 23 cm per year. -7 The corresponding rainfall per hour is 27 cm per year. -8 The corresponding rainfall per hour is 33 cm per year. a =0.278*I a *F(m 3 / s) to calculate the peak flow under the corresponding annual exceedance frequency.

[0054] Step c): According to Calculate the flood height h of the plant area under the corresponding annual exceedance frequency a .

[0055] Step d): Calculate the flood flow rate that spreads into the powerhouse at the corresponding annual exceedance frequency:

[0056] Q0=C e bh0(2g(h-Δh)) 0.5 .

[0057] Step e): Establish a water level calculation model for the nuclear power plant and calculate the water level in each room based on Q0.

[0058] Step f): Provide the installation location, elevation and waterproof information of the main transformer, battery, emergency diesel engine, condensate pump, plant water pump and circulating water pump. According to the data calculated in step e, determine the flooding situation of each electrical equipment, and determine the availability status of these electrical equipment according to the waterproof information of the equipment.

[0059] Step g): Establish a PSA model, take the calculation result of step f) as the initiating event, calculate CCDP, and further calculate CDF and LRF. Thus, the heavy rainfall probability safety assessment result is obtained, which, combined with the meteorological forecast, can effectively assess the safety of nuclear power plants under extreme weather conditions.

[0060] The above process can be automatically executed by the simulation software integrated in the safety control system of the nuclear power plant, and automatically updated according to the changes and accumulation of meteorological data and nuclear power plant operation data.

[0061] The purpose of the above embodiments is to further explain the present invention in detail in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, the optimization or equivalent replacement of the method steps involved, and the combination of the implementation methods in different embodiments without conflict of structure and principle, all fall within the protection scope of the present invention.

Claims

1. A method for safety assessment of heavy rainfall probability in a nuclear power plant, characterized in that: The following steps are involved: Step a): providing historical rainfall data, and fitting and extrapolating the historical rainfall data to obtain a heavy rainfall hazard curve that characterizes the corresponding relationship between rainfall intensity and annual exceedance frequency; Step b): providing a plurality of rainfall intensities and calculating the corresponding plant area flood peak flows, and determining the frequency corresponding to the plant area flood peak flows according to the heavy rainfall hazard curve; Step c): Calculate the flooding level of the plant area under different rainfall intensities; Step d): Calculating the flood flow spreading into the factory building according to the flooding water level in the factory area; Step e): Calculating the flood levels of different areas in the plant based on the flood flow spreading into the plant; Step f): Calculating the availability of a given electrical device according to the calculation result of step e); Step g): establishing a heavy rainfall PSA model according to the calculation result of step f), and calculating the core damage frequency caused by heavy rainfall.

2. The heavy rainfall probabilistic safety assessment method for a nuclear power plant according to claim 1, characterized in that: In the step b), the peak flow calculation of the plant area takes all rainfall as the peak flow.

3. The heavy rainfall probabilistic safety assessment method for a nuclear power plant according to claim 2, characterized in that: In the step b), the peak flow rate Q of the plant area with an annual exceeding frequency of a a The calculation method is Q a =0.278I a F, where I a is the hourly rainfall intensity when the annual exceedance frequency is a, and F is the catchment area.

4. The heavy rainfall probabilistic safety assessment method for a nuclear power plant according to claim 3, characterized in that: In the step c), the flood level h of the plant area corresponding to the annual exceeding frequency a a Solved by the broad crested weir overflow formula: Where m is the discharge coefficient and l is the overflow length of the wide crest weir.

5. The heavy rainfall probabilistic safety assessment method for a nuclear power plant according to claim 4, characterized in that: In step d), the calculation method of the flood flow Q0 spreading into the factory building is: Q0 = C e bh0(2g(h-Δh)) 0.5 , where Ce is the contraction coefficient, b is the width of the water inlet channel, h0 is the height of the water inlet channel, g is the gravitational acceleration, and Δh is the height difference between the plant floor and the plant ground.

6. The heavy rainfall probabilistic safety assessment method for a nuclear power plant according to any one of claims 1 to 5, characterized in that: In the step f), the given electrical equipment includes a main transformer, a battery, an emergency diesel engine, a condensate pump, a service water pump and a circulating water pump.

7. The method for probabilistic safety assessment of heavy rainfall in a nuclear power plant according to any one of claims 1 to 5, characterized in that: In the step g), the method for calculating the frequency of core damage caused by heavy rainfall is to substitute the availability result of the given electrical equipment calculated in the step f) into the heavy rainfall PSA model, calculate the conditional core damage probability caused by rainfall of different intensities, and calculate the frequency of core damage caused by heavy rainfall from the core damage probability caused by heavy rainfall.

8. The method for heavy rainfall probability safety assessment of a nuclear power plant according to claim 7, characterized in that: The step g) also includes a step of calculating the frequency of large-scale radioactive release caused by heavy rainfall.

9. A computing device, comprising a memory and a processor, characterized in that: The memory stores a calculation program, which, when executed by the processor, can implement the heavy rainfall probabilistic safety assessment method for a nuclear power plant as described in any one of claims 1 to 8.

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