System and method for identifying horizontal position of contamination on body surface of radiation worker during whole-body internal contamination monitoring

Abstract

The present invention relates to a system for identifying the horizontal position of contamination on the body surface of a radiation worker and, more specifically, to a system for identifying the horizontal position of contamination on the body surface of a radiation worker during whole-body internal contamination monitoring for identifying a contamination position of an external radioactive material which may exist on the body surface before measuring internal radioactive contamination of radiation workers. According to the present invention, the system comprises: a stand-type whole-body counter for monitoring a radioactive material present on the body surface during whole-body internal contamination monitoring of a radiation worker; radiation detectors disposed in a horizontal direction in the stand-type whole-body counter to individually measure radiation generated on the body surface of the radiation worker; and a horizontal position determination unit which determines the horizontal position of a radiation contamination source by calculating a relative ratio of a radiation count value, and derives coordinates of the contamination source by using an ellipse equation and the calculated relative ratio value. Therefore, the system can accurately identify the horizontal position of contamination on the body surface of the radiation worker. Accordingly, it is possible to increase the accuracy of measurement of internal radiation contamination, prevent unnecessary overestimation, and create a safe monitoring environment.

Description

System and method for verifying the horizontal position of surface contamination of a radiation worker's body during whole-body contamination examination

[0001] The present invention relates to a system for verifying the horizontal location of surface contamination of a radiation worker's body, and more specifically, to a system for verifying the horizontal location of surface contamination of a radiation worker's body during a whole-body contamination examination to identify the location of contamination of external radioactive materials that may be present on the body surface before measuring internal radioactivity contamination of radiation workers.

[0002] A Stand Type WBC (Whole Body Counter) using two large NaI detectors is used for whole-body contamination testing of radiation workers at nuclear power plants.

[0003] Figure 1 shows a stand-type whole-body contamination meter.

[0004] Figure 2 shows a phantom for radiation measurement. This model mimics the body of a radiation worker and is used to simulate and evaluate the state of radiation contamination inside and outside the body using a Whole Body Counter (WBC). The phantom is set with subdivided areas corresponding to various body parts, which allows for more precise analysis of the location and degree of contamination of radioactive materials.

[0005] Figure 3 shows the measurement ratio of the upper and lower detectors of the WBC in the event of external contamination. Figure 3 is a graph showing the ratio of radiation counts measured by the upper and lower detectors of the WBC (Whole Body Counter) under external contamination conditions. In the graph, the x-axis represents the cross-sectional number of the human body model, and the y-axis represents the count ratio (%) of each detector.

[0006] Regarding the upper detector, the solid line at the top of the graph in Fig. 3 shows the change in the counting ratio of the upper detector. It indicates a high ratio in areas close to the upper body. Regarding the lower detector, the counting ratio of the lower detector, indicated by the dotted line, indicates a higher value in areas close to the lower body. In other words, by comparing the counting ratios of the upper and lower detectors, the vertical location of the contaminant source can be identified. For example, if the counting ratio is measured higher in the upper detector, it can be determined that the contaminant source is located in the upper body.

[0007] To measure internal contamination in a radiation worker, external contamination on the worker's body surface must first be removed. If contamination is present on the outside of the worker's body, the distance to the WBC detector is reduced compared to when contamination is present on the inside, resulting in a larger value being counted by the detector. Therefore, if external contamination is considered internal contamination, the amount of radioactivity inside the human body is overestimated compared to the actual amount.

[0008] In domestic nuclear power plants, to distinguish between internal and external contamination, measurements are taken twice—on the front and the rear—and if the ratio is 2 or higher, it is considered external contamination. Subsequently, the location of vertical contamination can be identified using the counting ratio of the upper detector and the lower detector installed vertically in the WBC.

[0009] When using the above method, if there is contamination on the external surface of a radiation worker's body, there is a problem in that while the vertical location can be confirmed, the horizontal location of the external contamination cannot be confirmed.

[0010] [Prior Art Literature]

[0011] [Patent Literature]

[0012] (Patent Document 1) Republic of Korea Registered Patent 1665615 (October 6, 2016)

[0013] According to the present invention, the purpose is to provide a life assessment system for nuclear fuel fragment particles using long-half-life radionuclides to identify the location of contamination of external radioactive materials that may be present on the body surface before measuring internal radioactivity contamination of radiation workers.

[0014] According to the present invention, the apparatus includes a stand-type whole-body contamination detector (100) for inspecting radioactive material present on the body surface during a whole-body contamination inspection of a radiation worker, a radiation detector (200) that is horizontally positioned on the stand-type whole-body contamination detector and individually measures radiation generated from the body surface of the radiation worker, and a horizontal position determination unit (300) that determines the horizontal position of a radiation contamination source by calculating the relative ratio of radiation count values ​​based on the measurement results received from the radiation detector, and derives the coordinates of the contamination source using an elliptical equation and the calculated relative ratio value.

[0015] The stand-type whole-body contamination measuring instrument (100) includes a support structure for positioning the radiation detector (200) in a horizontal direction and is configured to fix the body of a radiation worker so as to allow for inspection.

[0016] The radiation detector (200) includes a NaI(Tl) detector and is positioned at a height of about 120 cm from the bottom surface of the stand-type whole-body contamination meter (100), spaced apart from each other by about 24 cm, and installed rotated at an angle of about 45° toward the radiation worker.

[0017] The horizontal position determination unit (300) calculates the relative ratio of the radiation count value received from the radiation detector (200), determines the horizontal position of the radiation source based on the calculated relative ratio, and derives the coordinates of the radiation source by applying an elliptical equation.

[0018] The NaI(Tl) detector of the radiation detector (200) individually measures radiation generated from the body surface of the radiation worker and transmits the measured data to the horizontal position determination unit (300).

[0019] Meanwhile, in a method using a horizontal position verification system for body surface contamination of a radiation worker during a full-body contamination examination, the method comprises: (a) a step in which the horizontal position verification system individually measures radiation generated from the body surface of a radiation worker through a radiation detector (200) arranged horizontally in a stand-type full-body contamination measuring device; (b) a step in which the horizontal position verification system collects radiation data measured through the radiation detector (200) and converts it into a radiation count value; (c) a step in which the horizontal position verification system determines the horizontal position of a radiation contamination source by calculating the relative ratio of the radiation count value received from the radiation detector; and (d) a step in which the horizontal position verification system derives the coordinates of a radiation contamination source based on the determined horizontal position and the calculated relative ratio value by applying an elliptic equation.

[0020] According to the present invention, the location of contamination on the body surface of a radiation worker can be accurately identified in the horizontal direction. This increases the accuracy of measuring internal radiation contamination, prevents unnecessary overestimation, and creates a safe inspection environment.

[0021] Figure 1 shows a stand-type full-body contamination meter according to the prior art.

[0022] Figure 2 shows a human phantom for radiation measurement according to the prior art.

[0023] Figure 3 shows the measurement ratio of the upper and lower WBC detectors during external contamination.

[0024] FIG. 4 is a front view of a system for confirming the horizontal position of surface contamination of a radiation worker's body during a whole-body contamination examination according to one embodiment of the present invention.

[0025] FIG. 5 is a side view of a system for confirming the horizontal position of surface contamination of a radiation worker's body during a whole-body contamination examination according to one embodiment of the present invention.

[0026] FIG. 6 shows the top view of a horizontal position verification system for surface contamination of a radiation worker's body during a whole-body contamination test according to one embodiment of the present invention.

[0027] Figure 7 shows the surface contamination coordinates (chest) of a horizontal position verification system for surface contamination of a radiation worker's body during a whole-body contamination examination according to one embodiment of the present invention.

[0028] Figure 8 shows the reactivity measured by an internal detector of a stand-type whole-body contamination measurement (WBC) according to the present embodiment.

[0029] Figure 9 shows the reactivity ratio of a horizontal direction detector of a system for confirming the horizontal position of a radiation worker's body surface contamination during a whole-body contamination test according to one embodiment of the present invention.

[0030] FIG. 10 is an example of the relative reactivity ratio of left and right NaI(TI) detectors in a horizontal position verification system for contamination on the body surface of a radiation worker during a whole-body contamination test according to one embodiment of the present invention.

[0031] FIG. 11 is a flowchart illustrating a method using a horizontal position verification system for surface contamination of a radiation worker's body during a whole-body contamination examination according to one embodiment of the present invention.

[0032] The present invention relates to a system for measuring radioactive material contamination on the body surface of a radiation worker and verifying the horizontal position by installing two NaI(Tl) detectors horizontally outside a Stand Type WBC.

[0033] Hereinafter, a system for confirming the horizontal position of surface contamination of a radiation worker's body during a whole-body contamination inspection according to the present embodiment will be described with reference to the attached drawings.

[0034] FIG. 4 is a front view of a system for confirming the horizontal position of surface contamination of a radiation worker's body during a whole-body contamination examination according to one embodiment of the present invention.

[0035] As shown in Fig. 4, two NaI(Tl) detectors are positioned at a height of about 120 cm from the bottom surface and are spaced about 24 cm apart from each other. They are arranged symmetrically with respect to the center of the phantom.

[0036] FIG. 5 is a side view of a system for confirming the horizontal position of surface contamination of a radiation worker's body during a whole-body contamination examination according to one embodiment of the present invention.

[0037] As shown in Fig. 5, each NaI(Tl) detector is installed rotated approximately 45 degrees toward the radiation worker. This increases the efficiency of the radiation detector and allows for more precise measurement of the source of contamination.

[0038] As illustrated in FIG. 4, the present invention relates to a system for determining the horizontal position when the surface of a radiation worker's body is contaminated with radioactive material by attaching two NaI(Tl) detectors horizontally to the outside of a Stand Type WBC and using the relative ratio of count values ​​measured by the detectors.

[0039] FIG. 6 shows the top view of a horizontal position verification system for surface contamination of a radiation worker's body during a whole-body contamination test according to one embodiment of the present invention.

[0040] As shown in Fig. 6, the detector is positioned to cover the chest, left arm, and right arm regions of the Phantom, allowing for detailed identification of the location of radioactive contamination in the horizontal direction.

[0041] As shown in FIGS. 4 and 6, two NaI(Tl) detectors are installed at a height of approximately 120 cm from the bottom surface of the Stand Type WBC. Each detector is installed rotated approximately 45 degrees toward the radiation worker. The distance between the two detectors is set to a distance of approximately 24 cm to the left and right of the center of the phantom.

[0042] The horizontal position verification of the horizontal position verification system according to the present embodiment is described as follows.

[0043] Two NaI(Tl) detectors each measure radiation emitted from the surface of the Phantom's body. The location of contamination is determined by comparing the relative ratio of the measured radiation count values.

[0044] For example, if the count value of the left detector is significantly higher than the count value of the right detector, it indicates that the radioactive material is located on the left surface of the Phantom's body.

[0045] The relative coordinates of the x-axis (left-right direction) and the y-axis (front-back direction) can be calculated through the ratio of coefficient values. This is precisely derived using elliptic equations and angle information. Through this structure and method, if there is radioactive contamination on the body surface of a radiation worker, the location can be accurately identified in the horizontal direction.

[0046] Figure 7 shows the surface contamination coordinates (chest) of a horizontal position verification system for surface contamination of a radiation worker's body during a whole-body contamination examination according to one embodiment of the present invention.

[0047] As shown in Fig. 7, the chest portion of the human body model Phantom is elliptical, with a major axis (a) of 15 cm and a minor axis (b) of 10 cm. The location of surface contamination is represented as (x, y), and the exact coordinates are calculated using the equation of an ellipse. Through this, the location of radioactive contamination present on the surface of the Phantom can be precisely identified in the horizontal and vertical directions.

[0048] The coordinates (x, y) of surface contamination can be calculated using the following equation.

[0049] In Fig. 7, if the location of surface contamination (white circle) is denoted as (x,y), x and y can be obtained by solving the following equations 1 and 2 simultaneously.

[0050] [Equation 1]

[0051]

[0052] Here, a is the radius of the major axis (horizontal direction) of the ellipse, which is 15 cm in the present invention. b is the radius of the minor axis (vertical direction) of the ellipse, which is 10 cm in the present invention. x is the horizontal coordinate of the surface of the phantom where the radioactive material is located. y is the vertical coordinate of the surface of the phantom where the radioactive material is located.

[0053] Equation 1 is the equation of an ellipse, indicating that all points on the Phantom surface lie on the elliptical boundary.

[0054] [Equation 2]

[0055]

[0056] Here, Equation 2 represents the slope of the tangent, where θ is the angle of the point where the radioactive material is located on the surface of the Phantom, and tanθ represents the slope of the tangent of the point, which is calculated as the ratio of the vertical coordinate to the horizontal coordinate.

[0057] [Equation 3]

[0058]

[0059] Here, x is the horizontal coordinate of the radioactive material on the surface of the phantom.

[0060] [Equation 4]

[0061]

[0062] Here, y is the vertical coordinate using the horizontal coordinate x and the slope tanθ.

[0063] The horizontal position verification system for surface contamination of a radiation worker's body during a whole-body contamination examination according to the present embodiment accurately derives the location of Phantom surface contamination by calculating the coordinates of the radioactive material using the geometric characteristics and slope of an ellipse.

[0064] This process is based on angles measured by radiation detectors, and utilizes the ratio of the major and minor axes to enable more precise positional analysis. This allows for the accurate identification of the location of contamination on the body surface of radiation workers.

[0065] Figure 8 shows the reactivity measured by an internal detector of a stand-type whole-body contamination measurement (WBC) according to the present embodiment.

[0066] Figure 8 shows the angle-dependent reactivity calculated using a stand-type WBC internal detector after positioning a Cs-137 source on a human body model phantom (chest) using Monte Carlo simulation. Here, the reactivity was calculated by increasing the height from 101 cm to 141 cm from the floor surface in 5 cm increments.

[0067] That is, Figure 8 shows the reactivity at different angles measured by a Stand Type WBC internal detector according to the present embodiment. Using Monte Carlo simulation, a Cs-137 source was placed on the chest area of ​​a human model phantom, and the reactivity measured at different angles through a Stand Type WBC internal detector was visualized.

[0068] Reactivity was calculated by increasing the height from 101 cm to 141 cm in 5 cm increments from the floor. For each height, reactivity was measured at angles from 0° to 360° relative to the position of the radioactive source. Figure 8 clearly shows the pattern of reactivity variation with height.

[0069] The reactivity curve exhibits a symmetrical pattern, reflecting the symmetry of the left and right sides of the body. Additionally, as height increases, the reactivity reaches a maximum value at a specific angle, suggesting that the sensitivity of the internal detector varies depending on the distance and angle from the source position.

[0070] This indicates that the location of internal or external radioactive material in the phantom can be determined more precisely based on the reactivity according to the angle and height of the internal detector of the Stand Type WBC.

[0071] As shown in Fig. 8, the reactivity measured by the Stand Type WBC internal detector is symmetrical, so the horizontal position of external body surface contamination cannot be determined.

[0072] Figure 9 shows the reactivity ratio of a horizontal direction detector of a system for confirming the horizontal position of a radiation worker's body surface contamination during a whole-body contamination test according to one embodiment of the present invention.

[0073] By utilizing the reactivity ratio of the horizontal detector installed through the present invention, the horizontal location of contamination on the external surface of the body can be determined. Figure 9 shows the results of simulating the efficiency of left and right NaI(Tl) detectors while attaching a Cs-137 source at a height of 101 cm to a human body model Phantom (chest) and rotating the position of the Cs-137 source 360° at 10° intervals. In Figure 9, the body positions by angle are as follows.

[0074] 0°: Right side

[0075] 90°: Back

[0076] 180°: Left side

[0077] 270°: Front side

[0078] Figure 9 visually shows the relative efficiency of the left detector and the right detector.

[0079] The black dotted line shows the efficiency of the left detector, and the gray dotted line shows the efficiency of the right detector. As the angle approaches 0°, the efficiency of the right detector increases, and as the angle approaches 180°, the efficiency of the left detector increases. This allows for the accurate determination of the horizontal position of the radiation source (CS-137). For example, the difference in efficiency between the left and right detectors is minimized at 90°, which indicates that the radiation source is located on the back of the body.

[0080] The results of this simulation demonstrate the utility of the present invention, which allows for the precise identification of the location of contamination on a radiation worker's body surface in the horizontal direction. The directionality of radioactive material can be effectively measured through the efficiency ratio of the NaI(Tl) detector.

[0081] FIG. 10 is an example of the relative reactivity ratio of left and right NaI(TI) detectors in a horizontal position verification system for contamination on the body surface of a radiation worker during a whole-body contamination test according to one embodiment of the present invention.

[0082] According to Fig. 10, the relative reactivity of the left and right NaI(Tl) detectors by angle is the result of dividing the efficiency of the left NaI(Tl) detector by the efficiency of the right NaI(Tl) detector. For example, when a Cs-137 source is located on the left side (180°), the ratio of the reactivity of the left NaI(Tl) detector to the right NaI(Tl) detector is approximately 4.2. This means that since the Cs-137 source is located on the left, the value counted by the left NaI(Tl) detector is approximately 4.2 times higher than that of the right NaI(Tl) detector.

[0083] In confirming directionality through relative reactivity, the relative reactivity of the left and right NaI(Tl) detectors clearly shows which side of the body the radiation source is located on.

[0084] For example, if the reactivity ratio is greater than 1, it means that the radioactive material is closer to the left, and if the ratio is less than 1, it indicates that it is closer to the right.

[0085] In terms of accurately determining the location of horizontal contamination, the relative reactivity ratio serves as a criterion for precisely identifying the horizontal position of a radiation source. This plays a role in distinguishing between external and internal contamination by identifying the location of contamination on the worker's body surface.

[0086] This invention demonstrates that the location of contamination on the body surface of a radiation worker can be effectively analyzed by utilizing relative reactivity data from a Whole Body Counter (WBC).

[0087] a=15 cm and b=10 cm, and since θ can be determined through the relative reactivity diagram in Fig. 10, the value of x can be calculated. By substituting x and tanθ into Equation (4), the value of y can be calculated, thus the (x,y) coordinate value in Fig. 7 can be calculated. Here, the sign of the x value is negative (-) if it is on the left side and positive (+) if it is on the right side. The sign of the y value is negative (-) if the contamination is on the front of the body and positive (+) if it is on the back side. Whether the contamination is located on the front or back of the body can be determined through the reactivity diagram in Fig. 8.

[0088] FIG. 11 is a flowchart illustrating a method using a horizontal position verification system for surface contamination of a radiation worker's body during a whole-body contamination examination according to one embodiment of the present invention.

[0089] As illustrated in FIG. 11, in a method using a horizontal position verification system for the surface contamination of a radiation worker's body (hereinafter referred to as the horizontal position verification system) during a full-body contamination test, the horizontal position verification system individually measures radiation generated from the surface of a radiation worker's body through a radiation detector (200) arranged horizontally in a stand-type full-body contamination measuring instrument (a).

[0090] Next, the horizontal position verification system collects radiation data measured through the radiation detector (200) and converts it into a radiation count value (b).

[0091] For reference, the radiation detector (200) detects radiation emitted from the body surface of a radiation worker and converts it into an electrical signal. The converted electrical signal is processed into digital data through a signal amplifier and an analog-to-digital converter (ADC). The processed digital data is converted into a radiation count value representing the intensity of the radiation and is recorded independently in each radiation detector. This process is performed automatically by a signal processing module within the radiation detector.

[0092] A radiation count is a value representing the number of radiation particles detected by a radiation detector over a certain period, serving as numerical data for the intensity of radiation. It is used to quantitatively assess the presence and amount of radiation. The reason for this conversion is as follows: Since radiation cannot be measured directly by the detector, signals generated by radiation (e.g., electrical pulses) are converted into digital data and recorded as count values. This allows for the precise calculation of radiation intensity and the identification of the location of contamination sources.

[0093] Next, the horizontal position verification system determines the horizontal position of the radiation source by calculating the relative ratio of radiation count values ​​received from the radiation detector (c).

[0094] Next, the horizontal position verification system derives the coordinates of the radiation source based on the horizontal position determined by applying the elliptic equation and the calculated relative ratio value (d).

[0095] The present invention has the effect of identifying the location of external contamination in the horizontal direction on the worker's body surface when performing a Stand Type WBC test.

Claims

1. A stand-type whole-body contamination detector (100) for detecting radioactive material present on the surface of the body during a whole-body contamination test of a radiation worker, A radiation detector (200) that is horizontally positioned on the above-mentioned stand-type whole-body contamination meter and individually measures radiation generated from the body surface of a radiation worker, A system for determining the horizontal position of a radiation worker's body surface contamination during a full-body contamination examination, comprising a horizontal position determination unit (300) that determines the horizontal position of a radiation contamination source by calculating the relative ratio of radiation count values ​​based on the measurement results received from the radiation detector, and derives the coordinates of the contamination source using an elliptical equation and the calculated relative ratio value.

2. In Paragraph 1, The above stand-type full-body contamination meter (100) is, It includes a support structure for positioning the above radiation detector (200) in a horizontal direction, A horizontal position verification system for surface contamination of a radiation worker's body during a whole-body contamination examination, characterized by being configured to allow the radiation worker's body to be fixed for examination.

3. In Paragraph 1, The above radiation detector (200) is, It includes a NaI(Tl) detector, A horizontal position verification system for the surface contamination of a radiation worker's body during a full-body contamination test, characterized by being positioned at a height of about 120 cm from the bottom surface of a stand-type full-body contamination meter (100), spaced apart from each other at a distance of about 24 cm, and installed rotated at an angle of about 45° toward the radiation worker.

4. In Paragraph 1, The above horizontal position determination unit (300) is, A system for verifying the horizontal position of a radiation worker's body surface contamination during a full-body contamination examination, characterized by calculating the relative ratio of radiation count values ​​received from the radiation detector (200), determining the horizontal position of a radiation source based on the calculated relative ratio, and deriving the coordinates of a radiation source by applying an elliptical equation.

5. In Paragraph 3, A system for confirming the horizontal position of contamination on the body surface of a radiation worker during a full-body contamination test, characterized in that the NaI(Tl) detector of the radiation detector (200) individually measures radiation generated on the body surface of a radiation worker and transmits the measured data to a horizontal position determination unit (300).

6. In a method using a horizontal position verification system for surface contamination of a radiation worker's body during a whole-body contamination examination, (a) A step in which the above horizontal position verification system individually measures radiation generated from the body surface of a radiation worker through a radiation detector (200) arranged horizontally in a stand-type whole-body contamination meter, (b) A step in which the horizontal position verification system collects radiation data measured through the radiation detector (200) and converts it into a radiation count value, (c) A step of determining the horizontal position of a radiation source by calculating the relative ratio of radiation count values ​​received from a radiation detector by the horizontal position verification system above; and (d) A method using a horizontal position verification system for radiation worker body surface contamination during a whole-body contamination examination, comprising the step of deriving the coordinates of a radiation contamination source based on a horizontal position determined by applying an elliptical equation to the horizontal position verification system and a calculated relative ratio value.

Images