Teste | Abstract: 151-1 | ||||
Abstract:Introduction: According to the International Commission on Radiological Protection (ICRP) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), workers who undergo occupational radiation exposure include all those exposed to radiation except for "(a) exposure to local natural background radiation; (b) exposure due to exempt activities involving radiation or exempt sources; and (c) any medical exposure of patients" (1,2). Occupational exposure is assessed through individual monitoring or personal radiation surveillance, typically using individual dosimeters that estimate the personal equivalent dose Hp(10) by simulating uniform whole-body irradiation (1). Personal dosimetry plays a crucial role in radiological protection by ensuring proper monitoring of workers exposed to ionizing radiation, aligning with the principles of radiological protection, particularly the comparison against dose limits. This study addresses the management and evaluation of anomalous results, such as unexpectedly high dose values, within the context of personal dosimetry services. Material and methods: Data: All occupational radiation workers in industrial and medical sectors with complete records, using whole-body dosimeters (Hp(10)), that exhibited anomalous dose values (high) during the period from 2015 to may 2024. Monitoring characteristics:The equiment used for the measurements consists of a dosimetric thermoluminiscense reader using TLD crystals of LiF: MgTI (MTS-N), each uniquely identified for occupationally exposed workers. Monitoring periods were 60 days for industry and conventional radiology, and 30 days for radiation therapy and nuclear medicine. Dose limits are in accordance with national regulations and international recommendations, and the annual individual effective dose has been set at 20 mSv averaged over 5 years, not exceeding 50 mSv in any single year, that was compared with the anomalous results. For conservative purposes, anomalous readings were defined as those exceeding 1.67 mSv, regardless of the monitoring period. An inspection of dosimeters that show anomalies is carried out to detect signs of contaminants or damage, and they are exposed to known doses to verify their functionality. It is generally recommended to the licensee to conduct investigations to identify the causes of high doses, and upon request recommendations are provided to staff on principles for dose reduction and good work practices. Results: During this period, there were 10 out of of a total of 195 occurrences of high doses exceeding 20 mSv in a single monitoring period. The maximum recorded doses were 66.51 mSv in 2017 and 72.03 mSv in 2022, clearly exceeding the annual limits permitted for occupational radiation exposure. More than 60% of the findings correspond to dosimeters used by male workers. Conclusions It is crucial to investigate and address the reasons behind these high doses to prevent future similar exposures and protect workers' health. Not all licensee holders reported the investigation results; in some cases, these anomalous doses were found to result from dosimeter misuse, for example, leaving it inside the X-ray room in diagnostic radiology. There was no evidence of intentional exposure in any case.
Keywords: Dose limit, Occupational Radiation Protection, Personal dosimetry |