Method for analyzing radiation dose to which thermoluminescent dosimeter element is exposed, and analysis device therefor

Abstract

The present invention relates to a method for analyzing a radiation dose to which a thermoluminescent dosimeter element is exposed, and to an analysis device therefor. The analysis method according to the present invention comprises the steps of: heating an exposed thermoluminescent dosimeter element and measuring light emitted for each channel according to temperature; converting the measured light into charge amounts to obtain a glow curve; and removing spikes corresponding to outliers from the glow curve, wherein the removing the spikes includes: for charge amounts of m consecutive channels, if a difference in charge amounts between the last two channels exceeds a threshold value, correcting the charge amount of the last channel by extrapolating charge amount of the preceding three channels, where m is an integer from 4 to 10.

Description

Method for analyzing radiation dose received by a thermoluminescent dosimeter element and analysis device for the same

[0001] The present invention relates to a method for analyzing the radiation dose received by a thermoluminescent dosimeter element and an analysis device for the same.

[0002] A thermoluminescent dosimeter (TLD) is equipment used by radiation workers to measure external radiation exposure. When a TLD is heated, electrons accumulated in the traps of the TLD element move to the valence band due to radiation; the radiation dose is measured by converting the light emitted during this process into an electric charge. Generally, the amount of electric charge generated according to the heating conditions of the TLD is represented by a glow curve.

[0003] If the TLD element is contaminated by dust or oil, light generated as the dust or oil burns during heating can enter the photomultiplier tube. This light appears as a spike on the glow curve and is considered an outlier. Furthermore, if the spike, which is not a signal caused by radiation, is not removed, the exposure dose will be overestimated compared to the actual dose.

[0004] Therefore, the objective of the present invention is to provide a method for analyzing the radiation dose exposed to a thermoluminescent dosimeter element in which spikes are effectively removed, and an analysis device for the same.

[0005] The objective of the present invention is achieved by a method for analyzing a radiation dose exposed to a thermoluminescent dosimeter element, comprising the steps of: heating the exposed thermoluminescent dosimeter element to measure light emitted by each channel according to temperature; converting the light into a charge amount to obtain a glow curve; and removing spikes corresponding to outliers from the glow curve, wherein in the removal of spikes, for the charge amounts of m consecutive channels, if the difference in charge amount between the last two channels is greater than a threshold value, the charge amount of the last channel is modified by extrapolating the charge amount of the preceding three channels, wherein m is an integer from 4 to 10.

[0006] The above channels consist of n channels, and the spike removal can be performed sequentially starting from channel 1 to channel n-m+1.

[0007] The above m can be 5 or 6.

[0008] The charge amount of the glow curve is expressed as a normalized intensity, and the threshold value may be 90% to 110% of 0.003.

[0009] The objective of the present invention is achieved by an apparatus for analyzing a radiation dose exposed to a thermoluminescent dosimeter element, comprising: an input unit that receives a glow curve obtained by heating the exposed thermoluminescent dosimeter element to measure light emitted by channel according to temperature and converting the light into a charge amount; a spike removal unit that removes spikes corresponding to outliers in the glow curve; and an output unit that outputs a modified glow curve with the spikes removed, wherein in the spike removal unit, for the charge amounts of m consecutive channels, if the difference in charge amount between the last two channels is greater than a threshold value, the charge amount of the last channel is modified by extrapolating the charge amount of the preceding three channels, where m is an integer from 4 to 10.

[0010] The above channels consist of n channels, and the spike removal can be performed sequentially starting from channel 1 to channel n-m+1.

[0011] The above m can be 5 to 6.

[0012] The charge amount of the glow curve is expressed as a normalized intensity, and the threshold value may be 90% to 110% of 0.003.

[0013] According to the present invention, a method for analyzing a radiation dose exposed to a thermoluminescent dosimeter element in which spikes are effectively removed, and an analysis device for the same are provided.

[0014] FIG. 1 is a flowchart of a radiation dose analysis method according to an embodiment of the present invention, and

[0015] Figure 2 is a diagram showing the occurrence of spikes in a glow curve, and

[0016] Figure 3 shows ΔR for setting the threshold value. i This represents the plot,

[0017] Figure 4 shows a glow curve with spikes removed, and

[0018] FIG. 5 is a configuration diagram of a radiation dose analysis device according to an embodiment of the present invention.

[0019] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0020] To clearly explain the present invention, parts unrelated to the explanation have been omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0021] In addition, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, so the present invention is not necessarily limited to what is illustrated.

[0022] The present invention may be used to measure the external radiation exposure dose of radiation workers at a nuclear power plant, though not limited thereto. Radiation workers wear a thermoluminescent dosimeter element (hereinafter TLD) during work and measure the exposure dose by analyzing the TLD after work.

[0023] The present invention will be described below with reference to the drawings.

[0024] FIG. 1 is a flowchart of a radiation dose analysis method according to an embodiment of the present invention.

[0025] First, the light emitted by channel from the exposed thermoluminescent dosimeter element is measured (S10).

[0026] TLDs may have different shapes and structures depending on their application and purpose. For example, a TLD chip may have a shape in which four chips are arranged on a single card. For example, materials such as LiF:Mg,Ti, Li2B4O7:Mn, CaF2:Mn, and CaSO4:Dy may be used.

[0027] When the TLD is heated, light is emitted by channel as the temperature increases. During heating, the temperature can be increased sequentially (step by step) from a first temperature to a second temperature. The temperature can be increased sequentially from the first temperature to the second temperature through multiple steps. There may be 200 steps of temperature, in which case 200 channels are obtained.

[0028] Next, the emitted light is converted into an electric charge to obtain a glow curve (S20).

[0029] The emitted light enters the interior of the photomultiplier tube through its window. When a high voltage is applied to the photomultiplier tube by a high-voltage power supply, the light is amplified, generating an electric current. The intensity of the current can be proportional to the magnitude of the radiation dose received. A current measuring device measures the intensity of the current generated in the photomultiplier tube. A recorder records the current intensity (i.e., intensity data) measured by the current measuring device according to the channel. The result recorded by the recorder in this manner is the glow curve.

[0030] Figure 2 is a diagram showing spike occurrences in the glow curve. Normalized intensities are displayed for 200 channels, and multiple spikes are observed.

[0031] Finally, spikes corresponding to outliers in the glow curve are removed (S30).

[0032] For spike removal, for the charge of m consecutive channels, if the difference in charge between the last two channels is greater than the threshold value, the charge of the last channel is modified by extrapolating the charge of the first three channels, where m is an integer from 4 to 10.

[0033] There are n channels, and spike removal is performed sequentially starting from channel 1 to channel n-m+1. If there are 200 channels and m is 5, spike removal is performed sequentially from channel 1 to channel 196.

[0034] As such, the present invention uses an extrapolation channel, and the spike removal when m is 5 in the concept of the extrapolation channel is explained as follows.

[0035] The extrapolation filter is R i , R i+1 , R i+2 , R i+3 , R i+4 , R i+5It consists of five entries. Here, i represents the channels of the glow curve, and if the glow curve consists of 200 channels, the extrapolation filter stops operating when i exceeds 196.

[0036] The extrapolation filter is R i+3 and R i+4 The difference (ΔR 34 R through comparison with a predetermined threshold value i+4 Determines if it is a spike. ΔR 34 If it is less than the threshold value, increment i by 1.

[0037] However, ΔR 34 If is greater than the threshold value, R i , R i+1 , R i+2 , R i+3 Linear regression of the value of to determine R for i i Convert the equation into a linear function. Then, using the slope and intercept of the resulting linear function, R i+4 PR to replace i+4 Create and increment i by 1.

[0038] Figure 3 shows ΔR for setting the threshold value. i This shows the plot. ΔR in the case where it is not a spike. i The range is -0.003 to 0.003, and in the case of a spike, ΔR i The range is -0.003 or less and 0.003 or greater. Based on this analysis, the threshold value can be set to 90% to 110% of 0.003.

[0039] Using the extrapolation filter described above, only the spikes can be removed without changing the readings (R) generated by radiation. For example, in Figure 4, the dots are raw data from channels 120 to 140 of the Glow curve, and the circles and triangles are the results of removing spikes using the extrapolation filter and the Whitaker-Hayes (WH) algorithm, respectively.

[0040] Since the WH algorithm smooths spikes using data before and after them, changes occur in the raw data after spike removal. On the other hand, using the extrapolation filter of the present invention allows for the removal of only the spikes, thereby preserving the raw data as much as possible.

[0041] FIG. 5 is a configuration diagram of a radiation dose analysis device according to an embodiment of the present invention. The analysis device may be configured as a computer and may communicate via the Internet or wired / wireless communication.

[0042] The analysis device (1) includes an input section (10), a spike removal section (20), and an output section (30).

[0043] The input unit (10) heats the exposed thermoluminescent dosimeter element to measure the light emitted by each channel according to temperature, and receives the glow curve obtained by converting the light into an electric charge.

[0044] The spike removal unit (20) removes spikes corresponding to outliers in the glow curve and can use the extrapolation filter described above.

[0045] The output unit (30) outputs a modified glow curve with spikes removed. Along with the glow curve, or instead, it may output channel-specific normalized intensity. The output form of the output unit (30) can be various, such as printing, screen display, storage, wired transmission, and wireless transmission.

[0046] According to the present invention described above, when reading a TLD, only spikes can be removed from the glow curve, so the exposure dose can be read using only the signal from the radiation without overestimating the exposure dose.

[0047] The aforementioned embodiments are examples for explaining the present invention, and the present invention is not limited thereto. Since a person skilled in the art to which the present invention pertains can implement the present invention by making various modifications therefrom, the technical scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for analyzing the radiation dose received by a thermoluminescent dosimeter element, A step of heating the exposed thermoluminescent dosimeter element to measure the light emitted by each channel according to temperature; A step of obtaining a glow curve by converting the above light into an electric charge; and The method includes the step of removing spikes corresponding to outliers from the above glow curve, In the above spike removal, for the charge amounts of m consecutive channels, if the difference in charge amount between the last two channels is greater than a threshold value, the charge amount of the last channel is modified by extrapolating the charge amount of the preceding three channels, and Here, m is an analysis method in which m is an integer from 4 to 10.

2. In Paragraph 1, The above channel consists of n channels, and The above spike removal is an analysis method performed sequentially starting from channel 1 to channel n-m+1.

3. In Paragraph 2, The above analysis method where m is 5 or 6.

4. In Paragraph 3, The charge of the above glow curve is indicated by normalized intensity, and The above threshold value is an analysis method in which 90% to 110% of 0.

003.

5. In a device for analyzing the radiation dose received by a thermoluminescent dosimeter element, An input unit that heats the exposed thermoluminescent dosimeter element to measure the light emitted by each channel according to temperature, and receives a glow curve obtained by converting the light into an electric charge; A spike removal unit for removing spikes corresponding to outliers in the above glow curve; and It includes an output unit that outputs a modified glow curve with the above spike removed, In the spike removal unit above, for the charge amounts of m consecutive channels, if the difference in charge amount between the last two channels is greater than a threshold value, the charge amount of the last channel is modified by extrapolating the charge amount of the preceding three channels. Here, m is an analysis device in which m is an integer from 4 to 10.

6. In Paragraph 5, The above channel consists of n channels, and The above spike removal is performed sequentially starting from channel 1 to channel n-m+1 in an analysis device.

7. In Paragraph 6, The above m is an analysis device in which m is 5 to 6.

8. In Paragraph 7, The charge of the above glow curve is indicated by normalized intensity, and An analysis device in which the threshold value is 90% to 110% of 0.003.

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