Correction method for air absorbed dose rate at the interface between land and water in aerial radioactivity measurement

Abstract

The present invention relates to a method for correcting the air absorption dose rate at the boundary between land and water during aerial radioactivity measurement, comprising the following steps: obtaining measurement data of an aerial radioactivity measurement mission area, and determining the coordinate range of the land area and the coordinate range of the water area within the aerial radioactivity measurement mission area; determining the measurement coordinate range that can be detected by a detector at each measuring point during aerial radioactivity measurement; calculating the land area ratio p within the range that can be detected by the detector at each measuring point; obtaining the relationship f(p) between the land area ratio p and the normalized air absorption dose rate at a height of 1 meter; correcting the measured air absorption dose rate at a height of 1 meter at the measuring point according to the land area ratio p and f(p) to obtain a corrected air absorption dose rate at a height of 1 meter; and filtering the corrected air absorption dose rate data at a height of 1 meter at the measuring point at the boundary between land and water. The data correction method of the present invention can correct the air absorption dose rate data at a height of 1 meter at the boundary between land and water measured by aerial radioactivity measurement.

Description

Technical Field

[0001] The invention relates to an environmental radiation measurement technology, in particular to a method for correcting air absorption dose rate at the land-water interface during aerial radioactivity measurement. Background Art

[0002] Aerial radioactivity measurement is a key technical tool for radiation environment investigations. The air absorbed dose rate at 1 meter above the ground, derived through processing of aerial radioactivity measurement data, is a key focus of radiation environment investigations and an important basis for assessing environmental radiation levels.

[0003] When using aerial radioactivity measurement methods to conduct radiation environment surveys, the aerial radioactivity measurement system is generally installed on an aircraft. During measurement, the aircraft is generally about 80 to 120 meters away from the ground. The effective measurement width of each measuring line to the ground is approximately twice the measured height above the ground. This allows for rapid acquisition of aerial radioactivity measurement data, and further enables the rapid acquisition of the air absorption dose rate at a height of 1 meter above the ground.

[0004] However, the aerial radioactivity measurement area may include both land and water areas. Since the concentration of radioactive elements in surface natural water bodies is much lower than that on land, the range covered by the aerial radioactivity measurement system at a single measuring point near the boundary between land and water will include both land and water areas. As a result, the 1m air absorption dose rate value at the land measuring point at the boundary between land and water will be affected by the water area and be lower. Conversely, the 1m air absorption dose rate value at the water measuring point at the boundary between land and water will be affected by the land area and be higher, resulting in the air absorption dose rate at the 1m height at the boundary between land and water being inconsistent with the actual value measured by aerial radioactivity.

[0005] In order to provide more accurate data on the air absorption dose rate at a height of 1m above the ground near the boundary between land and water, a correction method for the air absorption dose rate at the boundary between land and water in aerial radioactivity measurement is urgently needed. The air absorption dose rate data at a height of 1m obtained by actual calculation can be corrected to make the air absorption dose rate at a height of 1m at the boundary between land and water more consistent with the actual air absorption dose rate value at a height of 1m at this measuring point. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for correcting the air absorption dose rate at the boundary between land and water in aerial radioactivity measurement, so as to solve the problem that the air absorption dose rate at the boundary between land and water at a height of 1m measured by aerial radioactivity measurement does not match the actual value.

[0007] The present invention is achieved in this way: a method for correcting the air absorption dose rate at the water-land interface in aerial radioactivity measurement includes the following steps.

[0008] a. Obtain measurement data for the aerial radioactivity measurement mission area, calculate the measured air absorption dose rate at a height of 1m at each measuring point, and determine the coordinate range of the land area and the coordinate range of the water area within the aerial radioactivity measurement mission area.

[0009] b. Determine the measurement coordinate range that the detector can detect at each measuring point during aerial radioactivity measurement.

[0010] c. Calculate the proportion of land area within the range that can be detected by the detector at each measuring point, p, where p = land area / area that can be detected by the detector.

[0011] d. The Monte Carlo method was used to simulate and calculate the 1-m air absorption dose rate corresponding to different land area ratios p within the range that the detector can detect. The 1-m air absorption dose rate was normalized, and then the relationship f(p) between the land area ratio p and the normalized 1-m air absorption dose rate was obtained through one-dimensional interpolation calculation.

[0012] e. According to the land area ratio p and the relationship f(p) between the land area ratio p and the normalized 1-m air absorption dose rate, the measured 1-m air absorption dose rate at the measuring point is corrected to obtain the corrected 1-m air absorption dose rate.

[0013] f. Filter the corrected 1m height air absorption dose rate data of the measuring point at the boundary between land and water.

[0014] Furthermore, it is characterized in that in step d, the Monte Carlo method is used to simulate and calculate the 1m height air absorption dose rate corresponding to different land area proportions p within the range that can be detected by the detector. The specific method is: when performing Monte Carlo simulation, the source term settings and sampling rules of land and water are set: in the land area, it is assumed that the radioactive nuclides are uniformly distributed, and uniform sampling is used for source term setting; in the water area, no sampling is involved; then, according to the flight path of the aerial radioactivity measurement system and the relative position of the land-water boundary, a series of Monte Carlo models with land area proportions ranging from 0 to 1 within the detection range are constructed, and through multiple Monte Carlo simulation calculations, the 1m height air absorption dose rate corresponding to the land area proportions p in a series of detection ranges is obtained.

[0015] Furthermore, in step e, for land measurement points, use d i Indicates the measured 1m height air absorption dose rate at the measuring point, p i It represents the proportion of land area at the measuring point, and the corrected air absorption dose rate at 1m height is d′ i =d i / f(p i ).

[0016] For water measuring points, the air absorbed dose rate at the measuring point is corrected to the air absorbed dose rate at a height of 1 m at the water measuring point on the same measuring line, which is the closest land area to the measuring point and has a land area ratio of 0.

[0017] Furthermore, in step b, assuming that there are n measurement points in a certain measurement line, sorted by measurement time, the measurement point coordinate set is:

[0018] P={(x0,y0),(x i ,y i ),...(x n ,y n )}

[0019] Among them, x i ,y i are the north-south kilometer grid coordinates and the east-west kilometer grid coordinates of the i-th measuring point, respectively, in meters;

[0020] Measuring point P i The measurement range is the distance from the measuring point P during the flight. i-1 To measuring point P i The scanned area is:

[0021]

[0022] Where:

[0023] r i is the measuring point P i The detection radius of the position detector is equivalent to the height of the measuring point from the ground, in meters;

[0024] θ i is the vector P i-1 P i The angle with the horizontal axis of the coordinate system, in radians; sinθ i and cosθ i There are the following relationships:

[0025]

[0026] Furthermore, in step f, the 1 m height air absorbed dose rate data of the measuring point at the boundary between land and water are filtered using the cubic spline interpolation method.

[0027] Furthermore, using P a With P b Indicates the measuring points on both sides of the boundary between water and land, and their corresponding corrected air absorption dose rates are d′ a and d′ b ,according to

[0028] {(-5,d' a-2),(-3,d' a-1 ),(-1,d' a ),(1,d' b ),(3,d′ b+1 ),(5,d' b+2 )}

[0029] Perform one-dimensional interpolation on six points to obtain the interpolation function g(x); then according to

[0030]

[0031] The five points are interpolated by cubic spline to obtain the interpolation function h(x); then after filtering, P a With P b The air absorbed dose rates at a height of 1m are h(-1) and h(1) respectively.

[0032] The present invention uses the Monte Carlo method to simulate and calculate the 1-meter-high air absorption dose rate corresponding to different land area proportions p within the range that the detector can detect, thereby obtaining the relationship f(p) between the land area proportion p and the normalized 1-meter-high air absorption dose rate. f(p) is the Monte Carlo simulation coefficient. The air absorption dose rate is corrected according to the land area proportion and the Monte Carlo simulation coefficient, thereby avoiding mutual influence between water and land areas.

[0033] The data correction method of the present invention can correct the 1-meter-high air absorption dose rate data at the boundary between land and water areas measured by aerial radioactivity measurement, reduce the influence of the low radiation level in the water area on the land measurement points, reduce the influence of the radiation level in the land area on the water measurement points, and correct the 1-meter-high air absorption dose rate at the land measurement points and the water measurement points to a reasonable range, which is more in line with the actual 1-meter-high air absorption dose rate level of the land or water area corresponding to the measurement point. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a flow chart of a method for correcting air absorbed dose rate at the land-water interface in aerial radioactivity measurement.

[0035] Figure 2 It is a schematic diagram of the measurement range of the measuring point Pi of the present invention. i It is the detection radius of the detector at the measuring point, which is equivalent to the flight altitude above the ground.

[0036] Figure 3 This is a graph showing the relationship between the normalized 1m height air absorption dose rate and the land area ratio according to the present invention.

[0037] Figure 4 It is a schematic diagram of the air absorption dose rate data filtering processing method of the present invention.

[0038] Figure 5 This is the distribution map of air absorbed dose rate at a height of 1m at the junction of land and water in a certain area before and after correction. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] like Figure 1 As shown, the method for correcting the air absorption dose rate at the water-land interface in aerial radioactivity measurement of the present invention includes the following steps.

[0041] a. Obtain measurement data for the aerial radioactivity measurement mission area, calculate the measured air absorption dose rate at a height of 1m at each measuring point, and determine the coordinate range of the land area and the coordinate range of the water area within the aerial radioactivity measurement mission area.

[0042] b. Determine the measurement coordinate range that the detector can detect at each measuring point during aerial radioactivity measurement.

[0043] c. Calculate the proportion of land area within the range that can be detected by the detector at each measuring point, p, where p = land area / area that can be detected by the detector.

[0044] d. The Monte Carlo method was used to simulate and calculate the 1-m air absorption dose rate corresponding to different land area ratios p within the range that the detector can detect. The 1-m air absorption dose rate was normalized, and then the relationship f(p) between the land area ratio p and the normalized 1-m air absorption dose rate was obtained through one-dimensional interpolation calculation.

[0045] e. According to the land area ratio p and the relationship f(p) between the land area ratio p and the normalized 1-m air absorption dose rate, the measured 1-m air absorption dose rate at the measuring point is corrected to obtain the corrected 1-m air absorption dose rate.

[0046] f. Filter the corrected 1m height air absorption dose rate data of the measuring point at the boundary between land and water.

[0047] In step b, assuming that there are n measurement points in a certain measurement line, sorted by measurement time, the measurement point coordinate set is:

[0048] P={(x0,y0),(x i ,y i ),...(x n ,y n )}

[0049] Among them, x i ,y i are the north-south kilometer grid coordinates and the east-west kilometer grid coordinates of the i-th measuring point, respectively, in meters;

[0050] Measuring point P i The measurement range is the distance from the measuring point P during the flight. i-1 To measuring point P i The scanned area is:

[0051]

[0052] Where:

[0053] r i is the measuring point P i The detection radius of the position detector is equivalent to the height of the measuring point from the ground, in meters;

[0054] θi is the vector P i-1 P i The angle with the horizontal axis of the coordinate system, in radians; sinθ i and cosθ i There are the following relationships:

[0055]

[0056] In step d, it is characterized in that in step d, a Monte Carlo method is used to simulate and calculate the air absorption dose rate at a height of 1 m corresponding to different land area ratios p within the range that can be detected by the detector. The specific method is as follows: when performing the Monte Carlo simulation, the source term settings and sampling rules for the land and water areas are set: in the land area, the radioactive nuclides are assumed to be uniformly distributed and the source term settings are uniformly sampled; in the water area, the influence of the radioactive nuclides is negligible and therefore not sampled; then, based on the flight path of the airborne radioactivity measurement system and the relative position of the land-water boundary, a series of Monte Carlo models with land area ratios ranging from 0 to 1 within the detection range are constructed, and through multiple Monte Carlo simulations, the air absorption dose rate at a height of 1 m corresponding to the land area ratio p in the detection range is obtained. Specifically, it is assumed that the boundary line between the water area and the land area is a straight line, and the aircraft flies at a constant speed perpendicular to the boundary line. A certain number of measurement points are uniformly collected, and the land area ratio and the corresponding air absorption dose rate at each moment are calculated to obtain the air absorption dose rate corresponding to different ratios of the land area to the detector measurement area within the detection range of the detector.

[0057] In step e, for land measurement points, use d i Indicates the measured 1m height air absorption dose rate at the measuring point, p i Represents the land area ratio of the measuring point, then the corrected air absorption dose rate d′i =d i / f(p i ).

[0058] For a water measuring point, the air absorbed dose rate at the measuring point is corrected to the air absorbed dose rate of the water measuring point on the same measuring line whose land area ratio is 0 and is closest to the measuring point.

[0059] In step f, the cubic spline interpolation method is used to filter the 1m height air absorbed dose rate data of the measuring point at the boundary between land and water.

[0060] Use P a With P b Indicates the measuring points on both sides of the boundary between water and land, and their corresponding air absorption dose rate d′ a and d′ b According to {(-5,d' a-2 ),(-3,d' a-1 ),(-1,d' a ),(1,d' b ),(3,d' b+1 ),(5,d' b+2 )} Perform one-dimensional interpolation on six points to obtain the interpolation function g(x);

[0061] Based on

[0062]

[0063] The five points are interpolated by cubic spline to obtain the interpolation function h(x); then after filtering, P a With P b The air absorbed dose rates at a height of 1m are h(-1) and h(1) respectively.

[0064] Taking a certain area as an example, the 1m air absorption dose rate data calculated from the actual data at the junction of land and water during the aerial radioactivity measurement were corrected and converted into the actual 1m air absorption dose rate at this measuring point. The correction results are shown in Table 1.

[0065] Table 1

[0066]

[0067] In the table: FN-measuring point number; X-north-south kilometer grid coordinate, m; Y-east-west kilometer grid coordinate, m; D-air absorption dose rate at a height of 1 m above the ground, nGy / h; h-measurement height above the ground, m; p-proportion of land area within the measurement range of the measuring point, dimensionless; f(p)-correction factor; D'-corrected air absorption dose rate at a height of 1 m.

[0068] Depend on Figure 5 As can be seen from Table 1, the data correction method of the present invention can correct the air absorption dose rate data at a height of 1 m at the junction of land and water areas measured by aerial radioactivity measurement, reduce the impact of the low radiation level in the water area on the land measurement points, and reduce the impact of the radiation level in the land area on the water measurement points, and correct the air absorption dose rate at a height of 1 m at the land and water measurement points to a reasonable range, which is more in line with the actual air absorption dose rate level at a height of 1 m at the land or water area corresponding to this measurement point.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for correcting the air absorbed dose rate at the water-land interface during aerial radioactivity measurement, characterized in that: The following steps are involved: a. Obtain measurement data for the aerial radioactivity measurement mission area, calculate the measured air absorption dose rate at a height of 1m at each measuring point, and determine the coordinate range of the land area and the coordinate range of the water area within the aerial radioactivity measurement mission area; b. Determine the measurement coordinate range that the detector can detect at each measurement point during aerial radioactivity measurement; c. Calculate the land area percentage (p) within the range detectable by the detector at each measuring point, where p = land area / detectable area of ​​the detector; d. Use the Monte Carlo method to simulate and calculate the air absorption dose rate at a height of 1 m corresponding to different land area ratios p within the detector's detectable range. Normalize the air absorption dose rate at a height of 1 m, and then use one-dimensional interpolation to calculate the relationship f(p) between the land area ratio p and the normalized air absorption dose rate at a height of 1 m. e. Correct the measured 1m height air absorption dose rate at the measuring point based on the land area ratio p and the relationship f(p) between the land area ratio p and the normalized 1m height air absorption dose rate to obtain the corrected 1m height air absorption dose rate; f. Filter the corrected 1m height air absorption dose rate data of the measuring point at the boundary between land and water.

2. The method for correcting the air absorbed dose rate at the water-land interface in aerial radioactivity measurement according to claim 1 is characterized in that: In step d, the Monte Carlo method is used to simulate and calculate the air absorption dose rate at a height of 1 m corresponding to different land area proportions p within the range that the detector can detect. The specific method is as follows: when performing the Monte Carlo simulation, the source term settings and sampling rules for the land and water areas are set: in the land area, it is assumed that the radionuclides are uniformly distributed, and uniform sampling is used for the source term setting; in the water area, no sampling is involved; Then, based on the flight path of the aerial radioactivity measurement system and the relative position of the land-water boundary, a series of Monte Carlo models with the land area ratio within the detection range ranging from 0 to 1 were constructed. Through multiple Monte Carlo simulations, the 1-meter air absorption dose rate corresponding to the land area ratio p in a series of detection ranges was obtained.

3. The method for correcting the air absorbed dose rate at the water-land interface during aerial radioactivity measurement according to claim 1, characterized in that: In step e, for land measurement points, use d i Indicates the measured 1m height air absorption dose rate at the measuring point, p i It represents the proportion of land area at the measuring point, and the corrected air absorption dose rate at 1m height is d′ i =d i / f(p i ); For water measuring points, the air absorbed dose rate at the measuring point is corrected to the air absorbed dose rate at a height of 1 m at the water measuring point on the same measuring line, which is the closest land area to the measuring point and has a land area ratio of 0.

4. The method for correcting the air absorbed dose rate at the water-land interface during aerial radioactivity measurement according to claim 1, characterized in that: In step b, assuming that there are n measurement points in a certain measurement line, sorted by measurement time, the measurement point coordinate set is: P={(x0,y0),(x i ,y i ),...(x n ,y n )} Among them, xi and yi are the north-south kilometer grid coordinates and the east-west kilometer grid coordinates of the i-th measuring point, respectively, in meters; Measuring point P i The measurement range is the distance from the measuring point P during the flight. i-1 To measuring point P i The scanned area is: Where: r i is the measuring point P i The detection radius of the position detector is equivalent to the height of the measuring point from the ground, in meters; θi is the vector P i-1 P i The angle with the horizontal axis of the coordinate system, in radians; sinθ i and cosθ i There are the following relationships:

5. The method for correcting the air absorbed dose rate at the water-land interface during aerial radioactivity measurement according to claim 1, characterized in that: In step f, the cubic spline interpolation method is used to filter the 1m height air absorbed dose rate data of the measuring point at the boundary between land and water.

6. The method for correcting the air absorbed dose rate at the water-land interface during aerial radioactivity measurement according to claim 5, characterized in that: Use P a With P b Indicates the measuring points on both sides of the boundary between water and land, and their corresponding corrected air absorption dose rates are d′ a and d′ b ,according to {(-5,d' a-2 ),(-3,d′ a-1 ),(-1,d′ a ),(1,d′ b ),(3,d′ b+1 ),(5,d′ b+2 )} Perform one-dimensional interpolation on six points to obtain the interpolation function g(x); then according to The five points are interpolated by cubic spline to obtain the interpolation function h(x); then after filtering, P a With P b The air absorbed dose rates at a height of 1m are h(-1) and h(1) respectively.

Images