Nuclear power plant accident emergency air radiation monitoring method

Abstract

The invention provides a nuclear power plant accident emergency air radiation monitoring method. The method comprises the following steps: step 1, preliminarily generating a radioactive smoke plume diffusion situation based on a diffusion model; 2, estimating a radiation dose rate on a radioactive smoke plume axis; step 3, estimating intervention boundaries of five types of operation intervention levels OIL; 4, determining an actual intervention boundary based on ground gamma dose rate inversion measurement and calculation; 5, determining and dividing an aerial radiation monitoring task area; 6, planning an aerial radiation monitoring task; and step 7, air radiation monitoring flight control. According to the method provided by the invention, the nuclear radiation situation of the nuclear accident of the nuclear power plant can be scientifically determined, and the radiation monitoring area can be accurately divided and tasks can be allocated. According to the method, the planning optimization of the aerial nuclear radiation monitoring task and the optimal matching of the radiation monitoring task and the radiation monitoring equipment can be realized, the application efficiency of the aerial nuclear radiation monitoring equipment can be effectively improved, and the demand of the aerial radiation monitoring task on auxiliary decision making is met.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear radiation monitoring and application, in particular to an optimization algorithm-based method for emergency aerial radiation monitoring of nuclear power plant accidents. Background Art

[0002] Since the hazards of nuclear power plant accidents are characterized by wide range of nuclear radiation contamination and long duration, the rapid collection, transmission and processing of nuclear radiation monitoring information plays a prerequisite role in timely organizing emergency rescue and reducing the impact of radiation hazards on emergency rescue decisions. When performing nuclear emergency aerial radiation monitoring tasks, in order to complete the monitoring tasks in the shortest time and reasonably plan the task path and task allocation, it is necessary to carry out scientific task planning for aerial radiation monitoring equipment based on precise measurement, so as to accurately obtain the monitoring data such as the range, dose rate, and nuclide distribution of each radiation contaminated area in a short time. For aerial radiation monitoring, there are two situations: no wind and wind. When there is no wind, concentric circles, crosses, and petals are often used; when there is wind, serpentine return and scanning flight methods are often used; these flight monitoring methods are mostly based on meteorological conditions and dose rate distribution to implement monitoring, and cannot adapt to the optimal monitoring path and task allocation needs under different emergency mission environments. After an accident at a nuclear power plant, due to factors such as topography and meteorological conditions, the area, shape, and dose rate of the radiation hazard area are affected to varying degrees, and the differences in different hazard areas restrict the number and methods of using aerial radiation monitoring equipment. When performing aerial radiation monitoring tasks under specific conditions, in order to minimize mission time and improve monitoring efficiency, it is necessary to use optimization algorithms to scientifically allocate monitoring tasks and optimize radiation monitoring paths while meeting the constraints of radiation situation requirements and aerial emergency monitoring equipment indicators. Summary of the invention

[0003] The purpose of the present invention is to provide a fast and precise radiation monitoring method for airborne radiation monitoring equipment to perform emergency nuclear radiation monitoring after an accident in a nuclear power plant, which can be used for obtaining γ radiation situation and analyzing the distribution of radioactive nuclides and the diffusion of radioactive plumes under various conditions. In order to solve the above technical problems, adapt to the needs of rapid airborne radiation monitoring tasks for nuclear power plant accidents and accurately obtain the radiation situation of hazardous areas, we should focus on the estimation of radioactive plume diffusion in nuclear power plants, radiation dose rate estimation, intervention boundary measurement, γ dose rate inversion measurement, monitoring task area and division, etc., and reasonably determine the monitoring path and task allocation of airborne radiation monitoring. The present invention proposes an airborne nuclear radiation monitoring method based on task planning, which is based on the estimation of the scope of nuclear radiation monitoring tasks, in accordance with the idea of ​​"monitoring task measurement, monitoring path optimization, condition limit constraint, and reasonable task distinction", and on the basis of comprehensively considering relevant constraints, construct relevant optimization algorithms and models, optimize the monitoring path of airborne radiation monitoring equipment and reasonably distinguish tasks, maximize the guarantee efficiency of airborne emergency monitoring equipment, shorten the task time limit, and maximize emergency benefits.

[0004] The present invention is a method for nuclear power plant accident emergency aerial radiation monitoring based on mission planning, and the specific steps are as follows:

[0005] Step 1: Preliminary generation of radioactive plume diffusion trends based on the diffusion model

[0006] Assuming that the radiation source release point of the nuclear power plant is the source point, according to the Gaussian model, the continuous point source concentration distribution in the wind is measured according to the following formula:

[0007]

[0008] In the formula: c(x,y,z) is the concentration of radioactive substances at any point in space, and the unit is Bq·m -3 ; x, y, z represent the left, right, front, back, top and bottom coordinates of any point in space; Q is the radiation source intensity, the unit is Bq·s -1 ; u is the average wind speed, in m·s -1 ;k y ,k z is the turbulent diffusion coefficient, and its unit is m.

[0009] Since the concentration distribution on the cross section of the smoke cloud is a normal distribution, the lateral diffusion coefficient σ of the smoke cloud y and σ z for:

[0010]

[0011] Substituting into the above formula, it can be written as:

[0012]

[0013] Let z = 0, and we can get the ground concentration formula of radioactive nuclides:

[0014]

[0015] In the formula: c(x,y,0) is the concentration of radioactive substances at a point on the ground, in Bq·m -3 ; Q is the radiation source intensity, the unit is Bq·s -1 ; u is the average wind speed, in m·s -1 ; σ y and σ z is the lateral diffusion coefficient of the smoke cloud, in m. The turbulent diffusion coefficient is shown in the table below.

[0016]

[0017] Based on the above-mentioned Gaussian diffusion model of radioactive plume, combined with parameters such as the intensity of the radiation source released by the nuclear power plant at that time, the average wind speed, the height of the radiation source leakage location, etc., a preliminary diffusion trend of the ground radioactive plume can be generated.

[0018] Step 2: Estimation of radiation dose rate along the axis of the radioactive plume

[0019] Ground γ point source dose rate calculation formula:

[0020]

[0021] Where: D is the air absorption dose rate; A is the activity of the radioactive source, Γ is the irradiation rate constant of the corresponding nuclide; η is the linear attenuation coefficient of the corresponding nuclide; R is the distance between the point source and the monitoring point.

[0022] For points in the diffusion direction (downwind) of the radioactive plume, the radiation dose rate at a known position on the diffusion axis can be measured, and then the radiation dose rate at other downwind positions on the same axis can be measured by the inverse law. The calculation formula is as follows:

[0023]

[0024] Where: D1 is the radiation dose rate measured at r1, in mSv·h -1 ; D2 is the radiation dose rate measured at r2, in mSv·h -1 ; τ is the diffusion rate, which is related to the atmospheric stability. It is 1.5 in normal weather conditions, 2 when the atmospheric stability is a or b, 1.5 when the atmospheric stability is c or d, and 1 when the atmospheric stability is e or f. r1, r2 are the distances between any two monitoring points and the radiation source release point of the nuclear power plant, in meters.

[0025] Step 3: Estimation of intervention boundaries for five types of operational intervention levels (OILs)

[0026] According to GB / T 41577-2022 "Emergency Operational Intervention Levels for Nuclear Power Plants", the operational intervention levels are divided into 9 types. According to the standard OIL5 type (operational intervention level values ​​for preventive restrictions on general food and milk, the measurement category is ground deposition ambient dose equivalent rate), the dose rate limit is 1uSv / h, and the protective action taken is food restriction.

[0027] At a fixed monitoring point with a known monitoring distance r1 in a certain area of ​​a nuclear power plant, the gamma dose rate measured at the monitoring site is D1. According to the boundary value of the Class 5 operation intervention level 1uSv / h (D2), assuming that the atmospheric stability diffusion rate is 1.5, based on the diffusion axis radiation dose rate formula

[0028]

[0029] The intervention boundary distance r2 in the downwind direction of the emergency radiation monitoring area of ​​the aerial radiation monitoring equipment can be preliminarily estimated. Combined with the radioactive plume diffusion situation generated in the previous step 1 and the intervention boundary distance r2 in the downwind direction, the scope of the nuclear radiation monitoring task can be preliminarily estimated, providing a basic reference for task planning.

[0030] Step 4: Determine the actual intervention boundary based on ground gamma dose rate inversion

[0031] For regional nuclear radiation monitoring, although the aerial radiation monitoring equipment's flight path in the air is a very narrow straight line, the radioactive exposure to the aerial radiation monitoring equipment comes from a large surface source on the ground. The surface source is calculated by integrating the dose rate generated by multiple circular rings. The aerial radiation monitoring equipment is located at the center of the circular ring. The dose rate at different altitudes can be calculated using the following formula.

[0032]

[0033] Where: Ψ is the radius of the large surface source; r is the integration factor, corresponding to the radius of the ring; h is the flight altitude; ε is the surface contamination activity, which represents the radioactivity per unit area; Γ is the irradiation rate constant of the corresponding nuclide; is the linear attenuation coefficient of the corresponding nuclide.

[0034] Through a large number of experimental comparisons, for the same height, as the radius of the surface source increases, the dose rate gradually increases. When the source radius reaches more than 100m, the dose rate change is no longer obvious, so the surface source radius in the above formula can be taken as 100 meters. The formula can be expressed as:

[0035]

[0036] When performing emergency monitoring tasks, assuming that the aerial radiation monitoring equipment is flying at a certain meter altitude and measures the dose rate value of a certain contaminated point, the above-mentioned dose rate inversion formula can be used to measure the surface contamination activity (ε) of the contaminated point; and then the dose rate value 1 meter away from the contaminated point can be inverted and calculated. Near the estimated intervention boundary, the aerial radiation monitoring equipment should appropriately reduce the flight speed, and compare the ground γ dose rate value obtained in real time based on the inversion with the 5 types of operational intervention dose rate values, and then determine the actual intervention boundary.

[0037] Step 5: Determination and division of airborne radiation monitoring mission areas

[0038] According to GB / T 41577-2022 "Emergency Operation Intervention Level of Nuclear Power Plants", in the early emergency monitoring stage, the key land monitoring range is 30km, and the monitoring range can be gradually expanded to 50km according to the radioactive contamination situation; for large-scale radioactive releases caused by severe accidents in reactors with thermal power ≥1000MW, the monitoring range may need to be expanded to 80km or even farther. The specific emergency monitoring area should be reasonably determined in combination with the estimated nuclear radiation monitoring task scope, the diffusion situation prediction map and the national standard requirements to determine the approximate monitoring area for aerial radiation monitoring. According to the nuclear emergency plans of each nuclear power plant, the emergency planning area includes the smoke plume emergency planning area and the ingestion emergency planning area. The smoke plume emergency planning area is an emergency area centered on the nuclear power plant, divided into the smoke plume inner area (generally with a radius of 5km) and the outer area (generally with a radius of 10km); the radius of the ingestion emergency planning area is generally 30km or 50km. Accordingly, the contamination sector area downwind of the dominant wind direction is divided into different monitoring ranges with a radius of 5km, (5-10)km, (10-30)km, and (30-50)km. Specifically, within a radius of 5km, the mission area is equivalent to a rectangular area with a length of 5km and a width of the distance between the hot line and the longitudinal estimated intervention boundary; within a radius of 5-10km, the mission area is equivalent to a rectangular area with a length of 5km and a width of the distance between the hot line and the longitudinal estimated intervention boundary; within a radius of 10-30km, the mission area is equivalent to a rectangular area with a length of 20km and a width of the distance between the hot line and the longitudinal estimated intervention boundary; within a radius of 30-50km, the mission area is equivalent to a rectangular area with a length of 20km and a width of the distance between the hot line and the longitudinal estimated intervention boundary.

[0039] Aerial radiation monitoring adopts the method of equidistant parallel lines, covering the entire monitoring area along equidistant lines parallel to the vertical lines of the heat lines in the direction of smoke plume diffusion. The spacing between monitoring lines in different mission areas can be determined by referring to the following formula;

[0040]

[0041] Where: d is the distance between the parallel lines of radiation monitoring; D bThe natural background dose rate of the radiation monitoring environment; D z is the dose rate produced by the radionuclide at 1 meter.

[0042] The scanning parallel line spacings of different monitoring areas such as 5km, (5~10)km, (10~30)km, (30~50)km are d1, d2, d 3、 d4. The corresponding different monitoring areas can be further refined in monitoring methods. The monitoring area within 5km can be refined into a grid area; the monitoring areas within (5-10)km, (10-30)km, and (30-50)km are monitored using a scanning parallel return method. The actual airborne radiation monitoring mission area should be reasonably determined in combination with the preliminary estimated nuclear radiation monitoring mission scope and the above-mentioned monitoring methods.

[0043] Step 6: Airborne Radiation Monitoring Mission Planning

[0044] First, the total distance of aerial gamma radiation monitoring is calculated. According to the determined aerial nuclear radiation monitoring task range, the total distance of the aerial radiation monitoring path needs to be calculated, and the calculation formula is:

[0045]

[0046] Where: S represents the total distance of aerial radiation monitoring, unit: km; s1 s2 s3 s4 represent the lateral distances of the monitoring ranges with a radius of 5 km, 5-10 km, 10-30 km, and 30-50 km respectively; l1 l2 l3 l4 represent the distances between the hot lines and the longitudinal estimated intervention boundary at different monitoring radii in the direction of plume diffusion, unit: m; d1d2 d3 d4 represent the spacing between parallel radiation monitoring lines within the monitoring ranges with a radius of 5 km, 5-10 km, 10-30 km, and 30-50 km respectively, unit: m.

[0047] Secondly, the time calculation and task allocation of airborne gamma radiation monitoring. After estimating the total amount of airborne radiation monitoring tasks, the time and tasks of airborne radiation monitoring should be scientifically allocated based on the number and performance of emergency equipment performing the tasks, as well as related constraints such as the flight range, mission radius, monitoring speed, and tolerable cumulative dose.

[0048] The air radiation monitoring time is carried out according to the following formula:

[0049]

[0050] In the formula: S represents the total distance of aerial radiation monitoring, unit: km; n represents the number of aerial radiation monitoring equipment, unit: piece; v represents the radiation monitoring speed of the aerial radiation monitoring equipment, unit: km / h.

[0051] Relevant constraints:

[0052]

[0053] Based on the above constraints, given the number of aerial radiation equipment, the aerial radiation monitoring task can be optimized within the specified task time through reasonable task allocation.

[0054] Third, perform radionuclide identification on the contaminated area. The main function of radionuclide identification is to identify the types of radionuclides on the ground or in the air, and to find out the types, distribution and impact range of radionuclides leaked in nuclear power plant accidents. Since the radionuclide identification process can be performed alternately during γ dose rate monitoring, it is only necessary to select on the γ dose rate monitoring route, focusing on selecting points near hot lines or with high radiation intensity for radionuclide identification. During identification, it is necessary to hover at the corresponding position for more than 30 seconds, and then monitor after identification is completed. Radionuclide identification is divided into real-time identification and preset time identification. The specific application method is determined by emergency personnel based on actual conditions.

[0055] Step 7: Airborne Radiation Monitoring Flight Control

[0056] Combined with the mission planning of each aerial radiation monitoring device and the GIS map, the aerial radiation monitoring path of each monitoring device is generated and imported into the aerial radiation monitoring device control terminal. After arriving at the mission area, the aerial radiation monitoring device can autonomously perform radiation monitoring according to the mission planning path, or it can manually optimize the radiation monitoring path for real-time control based on the actual measured conditions.

[0057] During the mission, if the monitoring equipment flies too fast, it will affect the accuracy of the geographic reference position of the sensor data. At the same time, the detector data update rates of different monitoring equipment are different, and some are slower. A faster flight speed will cause the dose rate distribution to be too sparse. In order to generate a more accurate radiation situation, the flight speed should be determined based on the detector sensitivity, data update speed, and the sampling distance should not exceed 10 meters. The flight speed of the equipment should be reasonably determined.

[0058] During the mission, the monitoring equipment should not fly too high. The radiation dose rate is inversely proportional to the square of the distance. The flight altitude should be as low as possible to detect effective radiation data. Considering the difficulty of long-distance control of aerial radiation monitoring equipment due to terrain and objects, the flight altitude cannot be too low. When the aerial radiation monitoring equipment monitors along the scanning parallel line, its radiation detection system scans the surface source determined by the farthest detection distance, and the boundary conditions are determined by its flight altitude. Due to the sampling cycle of the detector, there are some areas that are not monitored by the detector during continuous flight. For this reason, the two staggered surface sources must be tangent to determine the flight altitude of the monitoring equipment. See the formula below.

[0059]

[0060] In the formula: P represents the maximum detection distance of the aerial radiation detector, unit: m; v represents the radiation monitoring speed of the aerial radiation monitoring equipment, unit: km / h; t' represents the sampling period of the detector, unit: s; d represents the spacing between monitoring lines in different mission areas of the aerial radiation monitoring equipment, unit: m.

[0061] To improve the accuracy of aerial monitoring data, the aircraft will hover at least once near the intersection of the scanning parallel line and the plume heat line, each hovering for about 10 seconds to accurately measure the actual radiation dose rate value at that point, thereby providing reliable data support for generating accurate nuclear radiation situation. After the flight, each monitoring device will integrate the monitoring data and fuse the situation, and finally display it on the GIS map in the form of a radiation situation heat map.

[0062] The present invention provides a fast and precise radiation monitoring method for aerial radiation monitoring equipment to perform emergency nuclear radiation monitoring after an accident at a nuclear power plant, which can provide decision support for aerial radiation monitoring equipment to optimize monitoring paths and reasonably distinguish tasks, maximize the protection efficiency of aerial emergency monitoring equipment, shorten task time limits, and maximize emergency benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for use in the embodiments or the prior art descriptions. The drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0064] Figure 1 The present invention is a flow chart of a method for emergency aerial radiation monitoring for nuclear power plant accidents.

[0065] Figure 2 It is a distribution map of ground radioactive contamination.

[0066] Figure 3a and Figure 3b This is a diagram of the spread of radioactive plumes.

[0067] Figure 4 This is a schematic diagram of the aerial nuclear radiation monitoring mission area.

[0068] Figure 5 This is a schematic diagram of the aerial nuclear radiation monitoring path. DETAILED DESCRIPTION

[0069] The implementation data of the present invention comes from the comprehensive application practice of aerial radiation monitoring equipment. According to the actual needs of the use of nuclear emergency monitoring equipment for aerial radiation monitoring tasks, the diffusion trend of ground radioactive plumes is determined through the radioactive plume Gaussian diffusion model and related parameters; the radiation dose rate on the axis of the radioactive plume is estimated based on the ground γ point source dose rate calculation formula; the estimated intervention boundary is based on 5 types of operational intervention levels (OIL); the actual intervention boundary is determined based on the ground γ dose rate inversion measurement; different monitoring methods are distinguished for different task radii of the land sector downwind of the dominant wind direction, and the aerial radiation monitoring task area is refined; the aerial radiation monitoring task volume is estimated, and scientific tasks are allocated based on relevant constraints; around the radiation situation generation, the flight speed, altitude, hovering and other actions of aerial radiation monitoring are precisely controlled.

[0070] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be systematically described below with the drawings in the embodiments. The embodiments described in the present invention are only part of the embodiments of the present invention, rather than all the embodiments.

[0071] Figure 1 This is a flow chart of the method for emergency aerial radiation monitoring of nuclear power plant accidents of the present invention. Taking aerial radiation monitoring of radiation hazard areas in a nuclear power plant accident as an example, the implementation steps are as follows:

[0072] Step 1: Preliminary generation of radioactive plume diffusion trends based on the diffusion model

[0073] Assume that the radiation source intensity of the nuclear power plant is 1.5×10 22 Bq / s, average wind speed is 5m / s, the height of the radiation source leakage is 26m, and the atmospheric stability is C. According to the ground concentration formula of radioactive nuclides:

[0074]

[0075] The concentration of radioactive substances at each point on the ground can be obtained by calculation, and then the distribution of ground radioactive contamination can be generated, such as Figure 2 As shown in Figure 2, the radioactive plume diffusion trend is as follows: Figure 3a and Figure 3b shown.

[0076] Step 2: Estimation of radiation dose rate along the axis of the radioactive plume

[0077] Assume that the main nuclides released from nuclear power plants are 235 U, based on the ground concentration formula of radioactive nuclides, it can be estimated that the activity of radioactive substances 50 meters away from the leakage location on the axis of the radioactive plume is about 9.5885×10 18 Bq·m -3The irradiation rate constant of the nuclide is 8.9×10 -2 The linear attenuation coefficient of the nuclide is 0.7, and the distance between the point source and the aerial radiation monitoring equipment is 50 meters. According to the ground γ point source dose rate calculation formula, it can be estimated that the dose rate value at 50 meters away from the leakage position on the axis of the radioactive plume is about 1.9mSv / h.

[0078] The ground radiation dose rate can be obtained in real time using the nuclear power plant's own fixed radiation monitoring equipment. Assuming that the fixed monitoring equipment is 100 meters away from the radioactive plume release location, the measured dose rate value is 0.8mSv / h. The radiation dose rate calculation formula for other downwind locations on the axis is:

[0079]

[0080] When the atmospheric stability is C, the diffusion rate is 1.5. According to the formula, the dose rate at a distance of 1000 meters from the release location of the radioactive plume can be calculated to be 0.025 mSv / h. From this, the distribution of radiation dose rate can be calculated, as shown in Table 1.

[0081] Table 1 Estimated dose rates at different distances from the release site of the nuclear power plant

[0082] r(km) 0.5 1.0 5.0 10.0 30.0 50.0 <![CDATA[D1(mSv / h)]]> 0.0716 0.025 0.0023 0.00046 0.00015 0.00007

[0083] Step 3: Estimation of intervention boundaries for five types of operational intervention levels (OILs)

[0084] According to the gamma dose rate measured at a fixed monitoring point in a certain area of ​​the nuclear power plant, the diffusion axis radiation dose rate formula and the 5th category of operational intervention level boundary value (1uSv / h), it can be preliminarily estimated that the downwind boundary distance of the emergency radiation monitoring area of ​​the aerial radiation monitoring equipment is approximately 8617 meters.

[0085] Step 4: Determine the actual boundaries of the five types of operational intervention levels based on ground gamma dose rate inversion

[0086] Through a large number of test comparisons, for the same height, as the radius of the surface source increases, the dose rate gradually increases. When the source radius reaches more than 100m, the dose rate change is no longer obvious, and the surface source radius can be taken as 100 meters. The dose rate formula for aerial radiation monitoring equipment at different heights can be expressed as:

[0087]

[0088] When performing emergency monitoring tasks, assuming that the aerial radiation monitoring equipment is flying at an altitude of 50 meters and measures the dose rate value of a certain contaminated point, the above-mentioned dose rate inversion formula can be used to measure the surface contamination activity (ε) of the contaminated point; with the help of the computing chip of the monitoring equipment, the dose rate value 1 meter away from the ground radiation source can be quickly inverted and calculated. On the scanning parallel lines about 8.4-9 kilometers away from the release location, the aerial radiation monitoring equipment can appropriately shorten the parallel line spacing, compare the ground γ dose rate value measured in real time by inversion with the dose rate value of the 5-category operation intervention level, and then accurately determine the actual monitoring intervention boundary.

[0089] Step 5: Determination and division of airborne radiation monitoring mission areas

[0090] According to the radiation dose rate calculation formula of other downwind positions on the axis:

[0091]

[0092] The natural background is usually 0.1uSv / h. It can be estimated that the distance to the normal natural background from the release location of the nuclear power plant is about 40km; according to the estimate, the radiation dose rate at 30 kilometers away from the release location is about 0.15uSv / h, which is not much different from the natural background. According to GB / T 41577-2022 "Emergency Operation Intervention Level of Nuclear Power Plants", in the early emergency monitoring stage, the key land monitoring range is 30km. By estimation, the downwind boundary distance of the boundary value of the 5th type of operation intervention level is about 9km.

[0093] Taking all the above factors into consideration, in order to accurately generate the nuclear radiation situation, scanning parallel return radiation monitoring is carried out in different ranges such as (0-5) km, (5-10) km, and (10-30) km of the land sector radius downwind of the dominant wind direction. Radiation monitoring is not currently implemented in the monitoring area within the range of (30-50) km. The schematic diagram of the aerial nuclear radiation monitoring mission area is as follows: Figure 4 shown.

[0094] The monitoring line spacing can be determined according to the following formula according to different mission areas;

[0095]

[0096] The measured scanning parallel line spacings of aerial monitoring in three different monitoring areas were 40 meters, 80 meters, and 140 meters, respectively.

[0097] Step 6: Airborne Radiation Monitoring Mission Planning

[0098] According to the total distance calculation formula of the aerial radiation monitoring path:

[0099]

[0100] In order to further improve the accuracy of task planning, the longitudinal estimated intervention boundary distance is taken every 5km in the monitoring area of ​​(10-30)km. The distances between the hot lines and the longitudinal estimated intervention boundary of different monitoring radii in the assumed direction of the smoke plume diffusion are: 0.5km, 1km, 1.5km, 2km, 2.5km, and 3km. It is estimated that the total monitoring distance is about 703km. Assume that the maximum monitoring range of a single aerial monitoring device is 400km, the maximum telemetry distance is 100km, the maximum allowable cumulative dose of the detector is 100Gy, the maximum aerial monitoring speed is 50km / h, and there are 2 aerial radiation monitoring devices. According to the formula, it can be calculated that the aerial radiation monitoring time is at least 7h. If the situation is urgent and the superior needs to quickly determine the ground radiation situation, the radiation monitoring of the smoke plume emergency plan area can be carried out first. It is calculated that the aerial radiation monitoring time is at least 2.5h. The schematic diagram of the aerial nuclear radiation monitoring path is as follows Figure 5 shown.

[0101] Step 7: Airborne Radiation Monitoring Flight Control

[0102] Combined with the air radiation monitoring equipment task planning and GIS map, the air radiation monitoring path of each monitoring equipment is generated and imported into the air radiation monitoring equipment control terminal. If the detector of the air radiation monitoring equipment updates the data once every 1 second, combined with the sampling distance should not exceed 10 meters, the speed of air radiation monitoring should be maintained at about 36km / h.

[0103] Assuming that the maximum detection distance of the airborne radiation monitoring equipment's detector at the boundary of the inner zone of the plume emergency plan is 100 meters, the flight speed of the airborne radiation monitoring equipment is 10m / s, the sampling period is 1s, and the parallel line spacing of the inner zone is known to be 40m, according to the flight altitude calculation formula, it can be concluded that the flight altitude of the airborne radiation monitoring equipment is about 97m. According to the dose rate estimate of the boundary of the outer zone of the plume emergency plan and the sensitivity of the detector, the ratio of the flight altitude of the outer zone to the inner zone of the plume emergency plan is about 1:2, so the flight altitude of the outer zone of the plume emergency plan is about 50m.

[0104] The aircraft hovers at least once near the intersection of each scanning parallel line and the plume heat line, hovering for about 10 seconds each time, to accurately measure the actual radiation dose rate value at that point. After the flight, each monitoring device integrates the monitoring data and fuses the situation, and finally displays it on the GIS map in the form of a radiation situation heat map.

[0105] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, and it should be clear that the present invention is not limited to the scope of the specific embodiments, for those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A method for monitoring radiation in the air during an emergency in a nuclear power plant accident, characterized in that: The steps include: Step 1: Preliminarily generate the radioactive plume diffusion situation based on the diffusion model; including: estimating the continuous point source concentration distribution when there is wind and preliminarily generating the ground radioactive plume diffusion situation; Step 2: Estimation of radiation dose rate on the axis of the radioactive plume; including: calculating the ground gamma point source dose rate on the axis of the radioactive plume and inferring the radiation dose rate in the downwind direction by the inverse law; Step 3: Estimation of intervention boundaries of the 5 types of operation intervention levels OIL; including: clarifying the dose rate values ​​of the 5 types of operation intervention levels boundaries and estimating the positions of the 5 types of operation intervention levels boundaries; Step 4: Determine the actual intervention boundary based on the ground gamma dose rate inversion measurement; including: clarifying the dose rate calculation formula of the airborne radiation monitoring equipment, inverting and calculating the dose rate value at 1 meter away from the contamination point, and determining the actual boundaries of the five types of operational intervention levels through real-time inversion measurement; Step 5: Determine and divide the aerial radiation monitoring task area; including: clarify the division of aerial radiation monitoring areas according to the dominant wind direction, clarify the scanning radiation monitoring line spacing formula, and calculate the scanning parallel line spacing of each radiation monitoring area; Step 6: Air radiation monitoring task planning; including: calculating the total distance of air y radiation monitoring, measuring the air y radiation monitoring time and task allocation based on constraints, and task planning for nuclide identification; Step 7: Aerial radiation monitoring flight control; including: mission planning path generation and import, air flight speed, altitude control and precise hovering measurement control, and generation of nuclear radiation situation heat map based on GIS map.

2. A method for emergency aerial radiation monitoring of nuclear power plant accidents according to claim 1, characterized in that: In step 1, the radiation source release point of the nuclear power plant is set as the source point. According to the Gaussian model, the continuous point source concentration distribution in the wind is measured according to the following formula: In the formula: c(x,y,z) is the concentration of radioactive substances at any point in space, and the unit is Bq·m -3 ; x, y, z represent the left, right, front, back, top and bottom coordinates of any point in space; Q is the radiation source intensity, the unit is Bq·s -1 ; u is the average wind speed in m·s -1 ;k y ,k z is the turbulent diffusion coefficient, in m; Since the concentration distribution on the cross section of the smoke cloud is a normal distribution, the lateral diffusion coefficient σ of the smoke cloud y and σ z for: Substituting into the above formula, we can write: Let z = 0, and we get the ground concentration formula of radioactive nuclides: In the formula: c(x,y,0) is the concentration of radioactive substances at a point on the ground, in Bq·m -3 ; Q is the radiation source intensity, the unit is Bq·s -1 ; u is the average wind speed in m·s -1 ; σ y and σ z is the lateral diffusion coefficient of the smoke cloud, in m.

3. A method for emergency aerial radiation monitoring of nuclear power plant accidents according to claim 1, characterized in that: In step 2, the ground gamma point source dose rate calculation formula is: Where: D is the air absorbed dose rate; A is the activity of the radioactive source, Γ is the irradiation rate constant of the corresponding nuclide; η is the linear attenuation coefficient of the corresponding nuclide; R is the distance between the point source and the monitoring point.

4. A method for emergency aerial radiation monitoring of nuclear power plant accidents according to claim 3, characterized in that: For points in the direction of radioactive plume diffusion, the radiation dose rate at a known position on the diffusion axis is measured, and then the radiation dose rate at other downwind points on the coaxial line is measured by the inverse law. The calculation formula is as follows: Where: D1 is the radiation dose rate measured at r1, in mSv·h -1 ; D2 is the radiation dose rate measured at r2, in mSv·h -1 ; τ is the diffusion rate, r1, r2 are the distances between any two monitoring points and the radiation source release point of the nuclear power plant, in meters.

5. A method for emergency aerial radiation monitoring of nuclear power plant accidents according to claim 1, characterized in that: In step 4, the dose rate generated by the surface source is integrated and calculated according to the multiple circular rings. The airborne radiation monitoring device is located at the center of the circular rings, and the dose rate at different heights is calculated using the following formula: Where: Ψ is the radius of the large surface source; r is the integration factor, corresponding to the radius of the ring; h is the flight altitude; ε is the surface contamination activity, which represents the radioactivity per unit area; Γ is the irradiation rate constant of the corresponding nuclide; is the linear attenuation coefficient of the corresponding nuclide.

6. A method for emergency aerial radiation monitoring of nuclear power plant accidents according to claim 5, characterized in that: For the same height, as the radius of the surface source increases, the dose rate gradually increases. When the source radius reaches more than 100m, the dose rate change is no longer obvious, so the surface source radius is taken as 100m; the formula is expressed as: When performing emergency monitoring tasks, assuming that the aerial radiation monitoring equipment flies at a certain height of one meter and measures the dose rate value of a certain contamination point, the surface contamination activity ε of the contamination point is measured through the dose rate inversion formula; then the dose rate value 1 meter away from the contamination point is inverted and calculated; near the estimated intervention boundary, the aerial radiation monitoring equipment should appropriately reduce the flight speed, and compare the ground γ dose rate value obtained in real time by inversion with the 5 types of operational intervention dose rate values ​​to determine the actual intervention boundary.

7. A method for emergency aerial radiation monitoring of nuclear power plant accidents according to claim 1, characterized in that: In step five, the contaminated sector area downwind of the dominant wind direction is divided into different monitoring ranges with a radius of 5 km, 5-10 km, 10-30 km, and 30-50 km. Specifically, within a radius of 5 km, the mission area is equivalent to a rectangular area with a length of 5 km and a width of the distance between the hot line and the longitudinal estimated intervention boundary; within a radius of 5-10 km, the mission area is equivalent to a rectangular area with a length of 5 km and a width of the distance between the hot line and the longitudinal estimated intervention boundary; within a radius of 10-30 km, the mission area is equivalent to a rectangular area with a length of 20 km and a width of the distance between the hot line and the longitudinal estimated intervention boundary; within a radius of 30-50 km, the mission area is equivalent to a rectangular area with a length of 20 km and a width of the distance between the hot line and the longitudinal estimated intervention boundary.

8. A method for emergency aerial radiation monitoring of nuclear power plant accidents according to claim 7, characterized in that: Aerial radiation monitoring adopts the method of equidistant parallel lines, covering the entire monitoring area along equidistant lines parallel to the perpendicular lines of the heat lines in the direction of smoke plume diffusion. The spacing between monitoring lines in different mission areas is determined by referring to the following formula; Where: d is the distance between the parallel lines of radiation monitoring; D b The natural background dose rate of the radiation monitoring environment; D z is the dose rate produced by the radionuclide at 1 meter.

9. A method for emergency aerial radiation monitoring of nuclear power plant accidents according to claim 1, characterized in that: In step six, the total distance of airborne gamma radiation monitoring is calculated; according to the determined airborne nuclear radiation monitoring mission range, the total distance of the airborne radiation monitoring path needs to be calculated, and the calculation formula is: Where: S represents the total distance of air radiation monitoring, unit: km; s1 s2 s3 s4 represent the lateral distances of the monitoring ranges with a radius of 5 km, 5-10 km, 10-30 km, and 30-50 km, respectively; l1 l2 l3 l4 represent the distances between the hot lines of different monitoring radii in the direction of the plume diffusion and the longitudinal estimated intervention boundary, in meters; d1 d2 d3d4 represent the distance between parallel radiation monitoring lines within the monitoring ranges with radii of 5km, 5-10km, 10-30km, and 30-50km, respectively, in meters; Time calculation and task allocation for airborne gamma radiation monitoring; After estimating the total amount of airborne radiation monitoring tasks, the time and tasks of airborne radiation monitoring should be scientifically allocated based on the number and performance of emergency equipment performing the tasks, as well as the relevant constraints of flight range, mission radius, monitoring speed, and tolerable cumulative dose. The air radiation monitoring time is carried out according to the following formula: Where: S represents the total distance of air radiation monitoring, unit: km; n represents the number of air radiation monitoring equipment, unit: piece; v represents the radiation monitoring speed of the airborne radiation monitoring equipment, unit: km / h; Relevant constraints: Carry out radionuclide identification in the contaminated area; because the radionuclide identification process is carried out alternately during the gamma dose rate monitoring, it is only necessary to select on the gamma dose rate monitoring route, focusing on selecting points near the hot line or with high radiation intensity for radionuclide identification. During identification, it is necessary to hover at the corresponding position for more than 30 seconds, and then monitor after the identification is completed.

10. A method for emergency aerial radiation monitoring of nuclear power plant accidents according to claim 1, characterized in that: In step seven, when the aerial radiation monitoring equipment monitors along the scanning parallel line, its radiation detection system scans the surface source determined by the farthest detection distance, and the boundary situation is determined by its flight altitude; due to the sampling cycle of the detector, there are some areas that are not monitored by the detector during the continuous flight process, and the two staggered surface sources must be tangent to determine the flight altitude of the monitoring equipment. The formula is: Where: Ρ represents the maximum detection distance of the airborne radiation detector, unit: m; v represents the radiation monitoring speed of the airborne radiation monitoring equipment, unit: km / h; t' represents the sampling period of the detector, unit: s; d represents the spacing between monitoring lines in different mission areas of aerial radiation monitoring equipment, unit: m.

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