Speaker
Description
Effective doses for occupational exposure of workers are estimated as internal and external doses. To properly manage protection for workers, internal contamination and exposure must be well controlled. Radiation workers may be exposed to radioactive materials in their work environment, so exposure must be continuously monitored. In Korea, thermoluminescent dosimeters (TLDs) are designated as legal dosimeters. However, dosimeters are normally used only for external exposure control. Applications for internal dose monitoring are difficult. There are several methods of detecting internal contamination, depending on the radionuclides. Gamma emitting radionuclides can be monitored using a whole body counting system (WBC) and alpha/beta nuclides are measured by analyzing excreta samples. Special analyzes should be performed after contamination above the threshold has been identified.
In this study, the screening conditions for measuring the internal contamination during work were studied. An on-site internal contamination screening vehicle named mobile radiobioassay laboratory (MRL) is used for this project. Screening conditions for urinalysis and WBC system were studied in this process to effectively monitor the contamination of workers.
Radiation workers were classified into military, education, research, and medical institutions. Field measurements consist of work records, whole body counts, urine collection and questionnaires for laboratory analysis. Based on the questionnaire, gamma and beta emitting radionuclides were selected capable of internal exposure. Gamma emitting radionuclides were monitored using the WBC of the MRL system. A separate pretreatment procedure was used for liquid scintillation counting (LSC) of tritium in urine samples. Other alpha/beta nuclides were screened using the LSC system. The critical level for internal contamination was derived taking into account the public dose limit of 1 and 0.1 mSv. Measurement time was determined in consideration of MDA, and actual measurement results and range of variation were investigated in some areas.
