국제표준규격의 137Cs 감마선장에서 전리함선량계 종류에 따른 공기커마율 측정 및 평가결과의 유효성 검증
Method Validation of the Measurement and Assessment Results of Air Kerma Rate by Type of Ionizing Chamber in 137Cs Gamma Field of International Standard
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In this study, air kerma was measured in field of the 137Cs gamma-ray irradiator using both farmertype and spherical type ionization chambers and was compared the results to determine whether they provide similarvalues under identical conditions. The gamma-ray field was established with an irradiator containing 137Cs isotopeof 370 GBq radioactivity and the customized conical collimator according to ISO 4037:2019. The air kerma rate at areference distance of 1 m from the source was measured using farmer type and spherical type ionization chambers,which maintain traceability through accredited calibration with identical environment condition. The assessed airkerma rate by the farmer type was 20.07 mGy h−1, with 3.1% uncertainty (confidence level : approx. 95%, k = 2) andthe spherical type was 20.11 mGy h−1, with 2.4% (confidence level: approx. 95%, k = 2), respectively. The result ofboth air kerma measurement shows good agreement. To verify the validation of dose measurement results throughKOLAS measurement audit was demonstrated that assessment of own dosimetry method conforms to internationalstandards. The measurement audit was conducted En-value evaluation through comparison of calibration factorincluding measurement uncertainty by using a spherical type of portable standard ionization chamber. The calibrationof measurement audit was performed at a reference air kerma rate of 3 mGy h−1. The results of our laboratory was3.731 × 104 Gy C−1, with 2.7% (confidence level: approx. 95%, k = 2) and the testing laboratory was 3.722 × 104 GyC−1, with 1.7% (confidence level : approx. 95%, k = 2), respectively. The En-value evaluation result was 0.08, whichis significantly smaller than the threshold value. It was shown that the objective precision and reliability of thedosimetry evaluation results have been verified. Overall, the own dose assessment method conform to internationalstandards and contribute to the advancement of radiation measurement techniques.
Abstract
In this study, air kerma was measured in field of the 137Cs gamma-ray irradiator using both farmertype and spherical type ionization chambers and was compared the results to determine whether they provide similarvalues under identical conditions. The gamma-ray field was established with an irradiator containing 137Cs isotopeof 370 GBq radioactivity and the customized conical collimator according to ISO 4037:2019. The air kerma rate at areference distance of 1 m from the source was measured using farmer type and spherical type ionization chambers,which maintain traceability through accredited calibration with identical environment condition. The assessed airkerma rate by the farmer type was 20.07 mGy h−1, with 3.1% uncertainty (confidence level : approx. 95%, k = 2) andthe spherical type was 20.11 mGy h−1, with 2.4% (confidence level: approx. 95%, k = 2), respectively. The result ofboth air kerma measurement shows good agreement. To verify the validation of dose measurement results throughKOLAS measurement audit was demonstrated that assessment of own dosimetry method conforms to internationalstandards. The measurement audit was conducted En-value evaluation through comparison of calibration factorincluding measurement uncertainty by using a spherical type of portable standard ionization chamber. The calibrationof measurement audit was performed at a reference air kerma rate of 3 mGy h−1. The results of our laboratory was3.731 × 104 Gy C−1, with 2.7% (confidence level: approx. 95%, k = 2) and the testing laboratory was 3.722 × 104 GyC−1, with 1.7% (confidence level : approx. 95%, k = 2), respectively. The En-value evaluation result was 0.08, whichis significantly smaller than the threshold value. It was shown that the objective precision and reliability of thedosimetry evaluation results have been verified. Overall, the own dose assessment method conform to internationalstandards and contribute to the advancement of radiation measurement techniques.