Site boundary atmospheric dispersion factor analysis method and system for small nuclear reactor

Abstract

The present invention relates to a site boundary atmospheric dispersion factor analysis method and system for a small nuclear reactor. The method comprises: when the distances from a reactor in all orientations are all greater than a preset distance, using a first calculation method to calculate atmospheric dispersion factor values in all orientations within a plurality of standard time periods; and when none of the distances from the reactor in one or more orientations is greater than the preset distance, if the release mode of a release source is selected to be ground-level release, using a second calculation method to calculate atmospheric dispersion factor values in all orientations within the plurality of standard time periods, and if the release mode of the release source is selected to be elevated release, using the first calculation method and the second calculation method to respectively calculate atmospheric dispersion factor values in all orientations within the plurality of standard time periods. Calculation using the two calculation methods in different cases effectively solves the problem of doses for personnel at site boundaries being close to limit values in current small nuclear reactor analysis, etc.

Description

Analysis method and system of atmospheric dispersion factors at the boundary of small nuclear reactor site

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311041085.3, filed on August 17, 2023, entitled “A method and system for analyzing atmospheric diffusion factors at the boundary of a small nuclear reactor site,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of nuclear power plant design, and in particular to a method and system for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site. Background Art

[0004] The short-term atmospheric diffusion factor (χ / Q) is a crucial input parameter for evaluating the off-site radiological consequences of post-accident and design basis accidents (DBA) in nuclear power plant siting. Its magnitude directly impacts the assessment of post-accident human doses. For traditional large nuclear reactors, the uninhabited area boundary (EAB) must be no less than 500 meters from the reactor, and the planning restricted zone (LPZ) must have a radius no less than 5 km. For locations farther from the reactor, such as the EAB and the outer boundary of the LPZ, the PAVAN program is typically used in the design and review of large nuclear power plants, in accordance with relevant regulations and guidelines. The maximum of the 95% probability horizontal atmospheric diffusion factor (χ / Q) for the entire site or the 99.5% probability horizontal atmospheric diffusion factor (χ / Q) for the azimuth is used as the atmospheric diffusion factor (χ / Q) at the EAB and outer boundary of the LPZ. This is used to analyze and assess the off-site radiological consequences of post-accident and DBA siting in early site applications, construction license applications, and operating license applications.

[0005] The inventors discovered that when the wind speed is low or the distance to buildings is close, the atmospheric diffusion factor calculated using the Gaussian plume model in the PAVAN program will be significantly higher, resulting in overly conservative results. Currently, the industry has not yet developed atmospheric diffusion factor analysis principles for site boundaries of small nuclear reactors. If the PAVAN program is also used to calculate short-term atmospheric diffusion factors in the safety analysis and environmental impact assessment of small nuclear reactors, it will easily cause the doses of hypothetical site selection accidents and design basis accidents at the site boundary to exceed the dose limits specified in the standards, thereby causing the site to fail the early site selection review.

[0006] Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention provides a method and system for analyzing the atmospheric diffusion factor at the boundary of a small nuclear reactor site, which can significantly optimize the accident dose assessment in the safety analysis and environmental impact assessment of small nuclear reactors, and can effectively solve the problem of personnel dose at the site boundary approaching the limit in the current small nuclear reactor analysis, thereby improving the adaptability of small nuclear reactor sites.

[0008] A first aspect of the present invention provides a method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site, comprising the following steps:

[0009] Determine the distance between the site boundaries and the reactor at all locations;

[0010] When the distances between all directions and the reactor are greater than the preset distances, the atmospheric diffusion factor values ​​at all directions within multiple standard time periods are calculated using the first calculation method;

[0011] When the distance between one or more directions and the reactor is not greater than the preset distance, the release mode of the release source is determined and selected;

[0012] When the release mode of the release source is selected as ground release, the second calculation method is used to calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods;

[0013] When the release mode of the release source is selected as elevated release, the atmospheric diffusion factor values ​​at all directions within multiple standard time periods are calculated using the first calculation method and the second calculation method respectively;

[0014] Among them, the first calculation method does not consider the influence of the wake effect caused by low wind speed and close buildings; the second calculation method considers the influence of the wake effect caused by low wind speed and close buildings.

[0015] Preferably, when the distances between all directions and the reactor are greater than the preset distance, the first calculation method is used to calculate the atmospheric diffusion factor values ​​at the 95% probability level for the entire site within multiple standard time periods, as well as the atmospheric diffusion factor values ​​at the 99.5% probability level for all directions.

[0016] Preferably, when the distance between one or more directions and the reactor is not greater than the preset distance, when the release mode of the release source is selected as ground release, the second calculation method is used to calculate the atmospheric diffusion factor value of the 95% probability level for the entire site within multiple standard time periods, and the atmospheric diffusion factor value of the 99.5% probability level for the direction where the distance between the site boundary and the reactor is less than the preset distance.

[0017] Preferably, when the distance between one or more directions and the reactor is not greater than a preset distance, when the release mode of the release source is selected as elevated release, the first calculation method and the second calculation method are used to respectively calculate the atmospheric diffusion factor values ​​of the 99.5% probability level for each direction within multiple standard time periods.

[0018] Preferably, the content of calculating the atmospheric diffusion factor value at the 99.5% probability level using the second calculation method includes:

[0019] The total number of calculated n-hour sliding average atmospheric diffusion factor values, where n is a constant;

[0020] The number of times the n-hour sliding average atmospheric diffusion factor value is exceeded by different atmospheric diffusion factor values ​​is calculated, and the adjacent threshold intervals in which the n-hour sliding average atmospheric diffusion factor value may fall at a 99.5% probability level are screened out;

[0021] Recalculate the n-hour sliding average atmospheric diffusion factor value at the 99.5% probability level based on the adjacent threshold intervals;

[0022] Calculate the atmospheric diffusion factor value within the time period m to n hours at the 99.5% probability level, where m is a constant.

[0023] Preferably, the first calculation method is to use the PAVAN program; the second calculation method is to use the ARCON96 program.

[0024] Preferably, when the release mode of the release source is selected as elevated release, the first calculation method and the second calculation method are used to respectively calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods. The values ​​of the atmospheric diffusion factor in each time period are as follows:

[0025] When p = 0 ~ 2hr,

[0026] When p = 2 to 8 hr or 8 to 24 hr,

[0027] When p = 24 to 96 hr or 96 to 720 hr,

[0028] Where, (χ / Q) p is the atmospheric diffusion factor value at the boundary of the small nuclear reactor site during period p; χ / Q is the atmospheric diffusion factor value; is the maximum value of the 99.5% probability level χ / Q values ​​of each direction in time period p calculated using the ARCON96 program; is the maximum value of the 99.5% probability level χ / Q values ​​of each direction in time period p calculated using the PAVAN program.

[0029] Preferably, when the ARCON96 program is used to calculate the atmospheric diffusion factor value at the 99.5% probability level, the following correction factor is introduced to correct the diffusion parameter:

[0030] in, is the correction factor in the horizontal or vertical direction; △σ v is the growth of disturbance in the lateral and vertical directions; t is the time from the release; T △v is the time scale of disturbance growth; R v (τ) is the Lagrangian autocorrelation function under the disturbance background; R v In actual calculations, (τ) can be assumed to be a constant in combination with relevant experimental measurement data.

[0031] A second aspect of the present invention provides a small nuclear reactor site boundary atmospheric dispersion factor analysis system, comprising:

[0032] The determination module is configured to: determine the distance between each site boundary and the reactor;

[0033] The first calculation module is configured to: when the distances between all directions and the reactor are greater than a preset distance, calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods using a first calculation method;

[0034] The second calculation module is configured to: when the distance between one or more directions and the reactor is not greater than the preset distance, if the release mode of the release source is selected as ground release, calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods using the second calculation method; if the release mode of the release source is selected as elevated release, calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods using the first calculation method and the second calculation method respectively;

[0035] Among them, when the first calculation method is used, the influence of the wake effect caused by low wind speed and close buildings is not considered; when the second calculation method is used, the influence of the wake effect caused by low wind speed and close buildings is considered.

[0036] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method for analyzing the atmospheric diffusion factor at the boundary of a small nuclear reactor site as described in the first aspect of the present invention.

[0037] The fourth aspect of the present invention provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the method for analyzing the atmospheric diffusion factor at the boundary of a small nuclear reactor site as described in the first aspect of the present invention are implemented.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] When the distances between all directions and the reactor are greater than a preset distance, the present invention adopts a first calculation method that does not consider the influence of the wake effect caused by low wind speed and close buildings to calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods; when the distances between one or more directions and the reactor are not greater than the preset distance, if the release mode of the release source is selected as ground release, the second calculation method that considers the influence of the wake effect caused by low wind speed and close buildings is used to calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods; if the release mode of the release source is selected as elevated release, the first calculation method and the second calculation method are respectively used to calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods; by calculating under different circumstances with the two calculation methods, the problem that the atmospheric diffusion factor calculated by simply using the Gaussian plume model will be significantly higher is avoided, the problem of the personnel dose at the site boundary approaching the limit value in the current small nuclear reactor analysis is effectively solved, and the adaptability of the small nuclear reactor site is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application.

[0041] FIG1 is a flow chart of a method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0043] When the wind speed is low or the distance to buildings is close, the atmospheric diffusion factor calculated using the Gaussian plume model in the PAVAN program will be significantly higher, resulting in overly conservative results. Currently, the industry has not yet established atmospheric diffusion factor analysis principles for the site boundaries of small nuclear reactors. If the PAVAN program is also used to calculate the short-term atmospheric diffusion factor in the safety analysis and environmental impact assessment of small nuclear reactors, it will easily cause the doses of hypothetical site selection accidents and design basis accidents at the site boundary to exceed the dose limits specified in regulatory standards, thereby causing the site to fail the early site selection review.

[0044] The accident dose limits for small nuclear reactors are much stricter than those for traditional large reactors. According to relevant regulations: in the event of a rare accident, the effective dose that individuals (adults) at the site boundary may receive during the entire duration of the accident (generally 30 days) should be controlled below 5 mSv, and the thyroid dose should be controlled below 50 mSv; in the event of an extreme accident, the effective dose that individuals (adults) at the site boundary may receive during the entire duration of the accident should be controlled below 10 mSv, and the thyroid dose should be controlled below 100 mSv. The relevant regulations applicable to traditional large-scale nuclear power plants are as follows: In the event of a rare accident, the effective dose to the public at the boundary of non-residential areas within 2 hours after the accident and the public at the boundary of planned restricted areas for the entire duration of the accident should be controlled below 5 mSv, and the thyroid equivalent dose should be controlled below 50 mSv. In the event of an extreme accident, the effective dose to the public at the boundary of non-residential areas within 2 hours after the accident and the public at the boundary of planned restricted areas for the entire duration of the accident should be controlled below 0.1 Sv, and the thyroid equivalent dose should be controlled below 1 Sv. Therefore, while small-scale nuclear power plants require a longer timeframe (30 days) for site boundary accident dose assessments, their dose limits are several times smaller than those of large-scale nuclear power plants.

[0045] Small nuclear reactors are typically targeted at markets such as replacing older, smaller thermal power plants and providing district heating and steam supply. As power sources for residential or industrial centers, they provide electricity, heat, and steam. They need to be built as close to users as possible to minimize energy transmission losses. This reduces site boundaries to effectively control reactor construction land, achieving intensive and economical land use. Therefore, site boundaries for small reactors are typically within 80 to 500 meters, and non-residential and restricted area boundaries often overlap with the site boundaries. At close distances from buildings, the overly conservative atmospheric dispersion factors calculated by the PAVAN program further increase the likelihood of accidental doses exceeding the limit at the site boundary.

[0046] Therefore, in order to meet more stringent dose requirements while taking into account the reduction of the site ratio boundary of small reactors, the off-site atmospheric diffusion factor analysis method used for traditional large reactors cannot be simply and crudely copied to the design system of small reactors. Instead, the analysis method of large reactors should be optimized and improved under existing conditions, or new analysis methods should be proposed for application to small reactors.

[0047] FIG1 is a flow chart of a method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site according to a specific embodiment of the present invention.

[0048] As shown in FIG1 , the method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site provided in this embodiment includes the following steps:

[0049] Step S1: Determine the distance between the site boundaries and the reactor in each direction. Different methods for calculating the atmospheric dispersion factor (χ / Q) are used depending on the distance.

[0050] In one embodiment, the area around the reactor site is divided into 16 directions, with the release point as the center, and the angle between each two adjacent directions is 22.5°. In step S1, when determining the distance between the site boundary and the reactor in each direction, the distances of all 16 directions should be considered.

[0051] In step S2, when the distance between all directions and the reactor is greater than a preset distance, the atmospheric diffusion factor (χ / Q) values ​​at all directions over multiple standard time periods are calculated using a first calculation method. Because the distance between all directions and the reactor is relatively large, the first calculation method does not consider the wake effects caused by low wind speeds and nearby buildings.

[0052] In one embodiment, the preset distance is 500m. Since the distance from the uninhabited area boundary (EAB) of a traditional large nuclear reactor (reactor with a single reactor thermal power greater than 300MW) to the reactor must not be less than 500m, for the small nuclear reactor (reactor with a single reactor thermal power not greater than 300MW) in this application, when the distance from all directions is greater than 500m, the influence of the wake effect caused by low wind speed and nearby buildings can be ignored when calculating the atmospheric diffusion factor value.

[0053] The low wind speed may be a wind speed as low as 0.5 m / s, and the optional range is a wind speed of 0.5 m / s to 1.5 m / s; the close distance may be a distance of at least 10 m, and the optional range is a range of 10 m to 500 m.

[0054] In a specific embodiment, the first calculation method may be performed using the PAVAN program. The first calculation method calculates the atmospheric diffusion factor values ​​at a 95% probability level within multiple standard time periods and the atmospheric diffusion factor values ​​at a 99.5% probability level in each direction.

[0055] In step S3, if the distance between one or more locations and the reactor is no greater than a preset distance, the release method of the release source is determined and selected. If the distance from the reactor is no greater than 500 meters, the atmospheric diffusion factor calculation method can be selected based on the release method of the release source.

[0056] Release sources typically include ground release and elevated release. Ground release refers to release directly from the factory building into the atmosphere without passing through a chimney. Elevated release applies to releases from independent, vertical, uncovered chimneys, etc., and is not affected by surrounding buildings. When the release height is greater than 2.5 times the height of surrounding buildings, or the following conditions are met, it is treated as an elevated release:

[0057] 1) The distance from the tail end of the upwind building exceeds 5L;

[0058] 2) The distance from the front of the downwind building exceeds 2L;

[0059] 3) The distance to the nearest edge of the building in the crosswind direction exceeds 0.5L;

[0060] L is the smaller of the height or width of the building that produces the upwind, downwind and crosswind wake effects respectively.

[0061] Step S4: When the release mode of the release source is selected as ground release, the second calculation method is used to calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods.

[0062] Since there is one or more locations with a distance from the reactor of no more than 500 and the release source is ground release, the second calculation method must take into account the influence of wake effects caused by low wind speed and nearby buildings.

[0063] In one embodiment, the second calculation method utilizes the ARCON96 program. The second calculation method calculates the atmospheric diffusion factor values ​​at a 95% probability level for the entire site over multiple standard time periods, as well as the atmospheric diffusion factor values ​​at a 99.5% probability level for locations where the distance between the site boundary and the reactor is less than a predetermined distance.

[0064] The calculation method of the atmospheric diffusion factor value at the 95% probability level for the entire site is as follows: take the minimum value of the 16-direction distance from the release point to the site boundary as the calculation input, calculate the atmospheric diffusion factor at the 95% probability level for each of the 16 directions, and take the maximum value of the atmospheric diffusion factor as the atmospheric diffusion factor at the 95% probability level for the entire site.

[0065] Step S5: When the release mode of the release source is selected as elevated release, the atmospheric diffusion factor values ​​at all directions within multiple standard time periods are calculated using the first calculation method and the second calculation method.

[0066] By using two calculation methods under different circumstances, the problem of significantly higher atmospheric diffusion factors obtained by simply using the Gaussian plume model is avoided. This effectively solves the problem of personnel doses at the site boundary approaching the limit in current small nuclear reactor analysis, and improves the adaptability of small nuclear reactor sites.

[0067] In step S2, if the distances between the 16 positions and the reactor are all greater than 500 m, the first calculation method is used for both ground release and elevated (chimney) release. Specifically, step S2 includes the following steps:

[0068] In step S21, the PAVAN program is used to calculate the χ / Q value of 99.5% probability level for 16 directions in each standard time period (0-2 hr, 2-8 hr, 8-24 hr, 24-96 hr, 96-720 hr).

[0069] In step S22, the PAVAN program is used to calculate the χ / Q value of the entire site at a 95% probability level for each standard time period (0-2 hr, 2-8 hr, 8-24 hr, 24-96 hr, 96-720 hr).

[0070] Step S23: Select the larger of the standard time periods as the χ / Q value of the small nuclear reactor site boundary.

[0071] Because the distance from the reactor in all directions is greater than 500 m, the wake effects caused by low wind speeds and nearby buildings can be ignored when calculating the χ / Q value. Therefore, using the first calculation method, the PAVAN program, to calculate the χ / Q value, a relatively ideal result is obtained.

[0072] In step S4, the release mode of the release source is ground release, and the second calculation method is used to calculate the χ / Q values ​​at all directions within multiple standard time periods, which specifically includes the following steps:

[0073] Step S41, using the ARCON96 program to calculate the χ / Q value of the 95% probability level of the entire site in each standard time period under the release mode.

[0074] In step S42, the ARCON96 program is used to calculate the χ / Q value corresponding to the 99.5% probability level of the direction where the distance between the site boundary and the reactor is less than or equal to 500 m.

[0075] In a specific embodiment, after using the ARCON96 program to calculate the χ / Q values ​​at all directions in multiple standard time periods in step S4, step S43 may also be included, in which the PAVAN program is used to calculate the χ / Q value at a 99.5% probability level for the directions corresponding to the distance between the site boundary and the reactor being greater than 500 m in each standard time period.

[0076] After the corresponding χ / Q values ​​are calculated through steps S41, S42, and S43 respectively, step S44 is executed to compare the χ / Q value of the 95% probability level of the entire site in each time period with the maximum value of the χ / Q value of the 99.5% probability level of each direction, and the larger one is selected as the χ / Q value of the boundary of the small nuclear reactor site.

[0077] Since the ARCON96 program can only output the χ / Q value of the 95% probability level for each standard time period, but cannot output the χ / Q value of the 99.5% probability level, step S42 includes the following steps to calculate the χ / Q value of the 99.5% probability level for each direction:

[0078] Step S421: Calculate the 95% probability level χ / Q value of the azimuth less than or equal to 500 m using ARCON96. Obtain the total number of n-hour (n=1, 2, 4, 8, ..., 720) sliding average χ / Q values ​​calculated by ARCON96, where n is a constant.

[0079] Step S422 , screening out the adjacent threshold intervals where the n-hour sliding average χ / Q value at the 99.5% probability level is most likely to fall.

[0080] Obtain the number of n-hour sliding average χ / Q values ​​calculated by the ARCON96 program that are exceeded by different χ / Q values, and use the following relationship to screen out the adjacent threshold intervals where the n-hour sliding average χ / Q value is most likely to fall at a 99.5% probability level:

[0081] Among them, %Exceedance represents the probability level, H total is the total number of n-hour slip average χ / Q values, H avg_int It is the number of n-hour sliding average χ / Q values ​​that are exceeded by a certain χ / Q value.

[0082] Step S423: recalculate the n-hour sliding average χ / Q value at the 99.5% probability level based on adjacent threshold intervals.

[0083] The following relationship is used to calculate the n-hour sliding average χ / Q value at the 99.5% probability level:

[0084] in, is the n-hour sliding average χ / Q value at the 99.5% probability level, and for The maximum and minimum values ​​of the adjacent threshold intervals that are most likely to fall within, %Exceedance,1 and %Exceedance,2 are Hehe The corresponding probability level.

[0085] Step S424: Calculate the atmospheric diffusion factor value within a time period of m to n hours at a 99.5% probability level, where m is a constant.

[0086] The χ / Q value within the time period of m to n hours at the 99.5% probability level is calculated using the following relationship:

[0087] Through the above steps S421 to S424, the χ / Q value corresponding to the 99.5% probability level of the direction where the distance between the site boundary and the reactor is less than or equal to 500m is calculated.

[0088] In one embodiment, before steps S41 and S42, a step S40 is further included, in which the following correction factors are introduced to correct the diffusion parameters to take into account the influence of low wind speed and wake effects of adjacent buildings when calculating the site boundary atmospheric diffusion factor of the ground release mode using the ARCON96 program:

[0089] in, is the correction factor in the horizontal or vertical direction, △σ v is the growth of disturbance in the lateral and vertical directions, t is the time from the release, T △v is the time scale of the disturbance growth, R v (τ) is the Lagrangian autocorrelation function under the disturbance background, R v In actual calculations, (τ) can be assumed to be a constant in combination with relevant experimental measurement data, and can take values ​​of 0.655 and 0.584 in the horizontal and vertical directions, respectively.

[0090] In step S4, when calculating the χ / Q value for the entire site at a 95% probability level using the ARCON96 program, the wind direction window should be 360°, and the distance from the release source to the receiving point should be the shortest distance between the release source and the boundary of the small nuclear reactor site. When calculating the χ / Q value for the 99.5% probability level for 16 azimuths, the wind direction window should be 45°, and the distance from the release source to the receiving point should be the shortest distance between the release source and the boundary of the small nuclear reactor site for each azimuth. The wind direction window refers to a certain angular range defined by the release point as the vertex and the line connecting the release point and the receiving point as the axis of symmetry.

[0091] In step S5, the release mode of the release source is elevated release, and the first calculation method and the second calculation method are used to respectively calculate the χ / Q value of the 99.5% probability level in each direction within multiple standard time periods, specifically including the following steps:

[0092] Step S51: PAVAN program is used to calculate the χ / Q value of each direction at a 99.5% probability level.

[0093] Step S52: Calculate the χ / Q value at the 99.5% probability level for each direction using the ARCON96 program.

[0094] Since the ARCON96 program can only output the χ / Q value at the 95% probability level for each standard time period, but cannot output the χ / Q value at the 99.5% probability level, in step S52, including steps S521, S522, S523 and S524, the χ / Q at the 99.5% probability level for each direction is calculated.

[0095] In step S521, ARCON96 is used to calculate the 95% probability level χ / Q value of each direction. The total number of n-hour (n=1, 2, 4, 8, ..., 720) sliding average χ / Q values ​​calculated by the ARCON96 program is obtained, where n is a constant.

[0096] Next, the calculations of steps S522, S523 and S524 are performed. The calculation method of step S522 is the same as that of step S422, the calculation method of step S523 is the same as that of step S423, and the calculation method of step S524 is the same as that of step S424.

[0097] Similarly, in one embodiment, before step S52, a further step S50 is included. When calculating the site boundary atmospheric dispersion factor for the elevated release mode using the ARCON96 program, a correction factor is introduced to correct the diffusion parameter to account for the effects of low wind speeds and the wake effects of adjacent buildings. The calculation method for the correction factor in step S50 is the same as that in step S40.

[0098] In step S51 and step S52, after respectively calculating the atmospheric diffusion factor values ​​at all directions within a plurality of standard time periods using the first calculation method and the second calculation method, the following steps are further included:

[0099] In step S53, the calculation results of step S51 and step S52 are compared, and the larger value is taken to obtain the χ / Q value of the small-scale reactor site boundary 0-2hr.

[0100] Step S54: Weighted calculation of the χ / Q values ​​for the small reactor site boundaries within the time ranges of 24-96 hr and 96-720 hr.

[0101] Specifically, the values ​​of the atmospheric diffusion factor for each time period are as follows:

[0102] When p = 0 ~ 2hr,

[0103] When p = 2 to 8 hr or 8 to 24 hr,

[0104] When p = 24 to 96 hr or 96 to 720 hr,

[0105] Where, (χ / Q) p is the atmospheric diffusion factor value at the boundary of the small nuclear reactor site during period p; χ / Q is the atmospheric diffusion factor value; is the maximum value of the 99.5% probability level χ / Q values ​​of each direction in time period p calculated using the ARCON96 program; is the maximum value of the 99.5% probability level χ / Q values ​​of each direction in time period p calculated using the PAVAN program.

[0106] Through the above steps S50 to S54, the χ / Q value in the elevated release condition is calculated.

[0107] The present invention also provides a small nuclear reactor site boundary atmospheric diffusion factor analysis system, comprising:

[0108] The determination module is configured to: determine the distance between each site boundary and the reactor;

[0109] The first calculation module is configured to: when the distances between all directions and the reactor are greater than a preset distance, calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods using a first calculation method;

[0110] The second calculation module is configured to: when the distance between one or more directions and the reactor is not greater than the preset distance, if the release mode of the release source is selected as ground release, calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods using the second calculation method; if the release mode of the release source is selected as elevated release, calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods using the first calculation method and the second calculation method respectively;

[0111] Among them, when the first calculation method is used, the influence of the wake effect caused by low wind speed and close buildings is not considered; when the second calculation method is used, the influence of the wake effect caused by low wind speed and close buildings is considered.

[0112] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the above-mentioned method for analyzing the atmospheric diffusion factor at the boundary of a small nuclear reactor site when executed by a processor.

[0113] The present invention also provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the above-mentioned method for analyzing the atmospheric diffusion factor at the boundary of a small nuclear reactor site are implemented.

[0114] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site, characterized in that: include: Determine the distance between the site boundaries and the reactor at all locations; When the distances between all directions and the reactor are greater than the preset distances, the atmospheric diffusion factor values ​​at all directions within a plurality of standard time periods are calculated using the first calculation method; When the distance between one or more directions and the reactor is not greater than the preset distance, the release mode of the release source is determined and selected; When the release mode of the release source is selected as ground release, the second calculation method is used to calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods; When the release mode of the release source is selected as elevated release, the atmospheric diffusion factor values ​​at all directions in multiple standard time periods are calculated using the first calculation method and the second calculation method respectively; Among them, the first calculation method does not consider the influence of the wake effect caused by low wind speed and close buildings; the second calculation method considers the influence of the wake effect caused by low wind speed and close buildings.

2. The method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site according to claim 1, characterized in that: When the distances between all directions and the reactor are greater than the preset distances, the first calculation method is used to calculate the atmospheric diffusion factor values ​​at the 95% probability level for the entire site within multiple standard time periods, as well as the atmospheric diffusion factor values ​​at the 99.5% probability level for all directions.

3. The method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site according to claim 1, characterized in that: When the distance between one or more directions and the reactor is not greater than the preset distance, when the release mode of the release source is selected as ground release, the second calculation method is used to calculate the atmospheric diffusion factor value of the 95% probability level for the entire site within multiple standard time periods, and the atmospheric diffusion factor value of the 99.5% probability level for the direction corresponding to the distance between the site boundary and the reactor is less than the preset distance.

4. The method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site according to claim 1, characterized in that: When the distance between one or more directions and the reactor is not greater than the preset distance, when the release mode of the release source is selected as elevated release, the first calculation method and the second calculation method are used to respectively calculate the atmospheric diffusion factor values ​​of the 99.5% probability level in each direction within multiple standard time periods.

5. The method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site according to claim 3 or 4, characterized in that: The content of calculating the atmospheric diffusion factor value at the 99.5% probability level using the second calculation method includes: The total number of calculated n-hour sliding average atmospheric diffusion factor values, where n is a constant; The number of n-hour sliding average atmospheric diffusion factor values ​​that are exceeded by different atmospheric diffusion factor values ​​is calculated, and the adjacent threshold intervals where the n-hour sliding average atmospheric diffusion factor values ​​with a probability level of 99.5% may fall are screened out; Recalculate the n-hour sliding average atmospheric diffusion factor value at the 99.5% probability level according to the adjacent threshold intervals; Calculate the atmospheric diffusion factor value within the time period of m to n hours at the 99.5% probability level, where m is a constant.

6. The method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site according to claim 1, characterized in that: The first calculation method uses the PAVAN program for calculation; the second calculation method uses the ARCON96 program for calculation.

7. The method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site according to claim 6, characterized in that: When the release mode of the release source is selected as elevated release, the first calculation method and the second calculation method are used to calculate the atmospheric diffusion factor values ​​at all directions in multiple standard time periods respectively. The values ​​of the atmospheric diffusion factor in each time period are as follows: When p = 0 ~ 2hr, When p = 2 to 8 hr or 8 to 24 hr, When p = 24 to 96 hr or 96 to 720 hr, Where, (χ / Q) p is the atmospheric dispersion factor value at the boundary of the small nuclear reactor site during the period p; χ / Q is the atmospheric dispersion factor value; is the maximum value of the 99.5% probability level χ / Q values ​​of each direction in time period p calculated using the ARCON96 program; It is the maximum value of the 99.5% probability level χ / Q value of each direction in time period p calculated using the PAVAN program.

8. The method for analyzing atmospheric dispersion factors at the boundary of a small nuclear reactor site according to claim 6, characterized in that: When using the ARCON96 program to calculate the atmospheric diffusion factor value at the 99.5% probability level, the following correction factors are introduced to correct the diffusion parameters: in, is the correction factor in the horizontal or vertical direction; △σ v is the growth of disturbance in the lateral and vertical directions; t is the time from the release; T △v is the time scale of disturbance growth; R v (τ) is the Lagrangian autocorrelation function under the disturbance background; R v In actual calculations, (τ) can be assumed to be a constant in combination with relevant experimental measurement data.

9. A small nuclear reactor site boundary atmospheric dispersion factor analysis system, characterized in that: include: The determination module is configured to: determine the distance between each site boundary and the reactor; The first calculation module is configured to: when the distances between all directions and the reactor are greater than a preset distance, use a first calculation method to calculate the atmospheric diffusion factor values ​​at all directions within a plurality of standard time periods; The second calculation module is configured to: when the distance between one or more directions and the reactor is not greater than a preset distance, if the release mode of the release source is selected as ground release, use a second calculation method to calculate the atmospheric diffusion factor values ​​at all directions within multiple standard time periods; If the release mode of the release source is selected as elevated release, the atmospheric diffusion factor values ​​at all directions in multiple standard time periods are calculated using the first calculation method and the second calculation method respectively; Among them, when the first calculation method is used, the influence of the wake effect caused by low wind speed and close-range buildings is not considered; when the second calculation method is used, the influence of the wake effect caused by low wind speed and close-range buildings is considered.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method for analyzing the atmospheric dispersion factor at the boundary of a small nuclear reactor site as described in any one of claims 1 to 8 are implemented.

11. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the atmospheric dispersion factor analysis method for a small nuclear reactor site boundary are implemented as described in any one of claims 1-8.

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