Screening Criteria for the General Public in Radiation Emergencies From Liquid Scintillation Urinalysis

Gross alpha/beta screening of urine samples was performed to evaluate internal contamination and dose assessment. Data on background radioactivity concentration were extracted by analyzing the urine samples of non-contaminated individuals who had visited a radiation effect medical clinic since 2012. Screening criteria were studied and established for radiation emergencies based on these results. In particular, pure beta-emitting radionuclides (H and Sr) with a high dose conversion factor were considered to be the source of contamination. Moreover, the screening criteria for the general public were determined based on age groups. The liquid scintillation counting method was used for gross alpha/beta radiation counting. A standardized procedure of correction for chemical and color quenching was performed and validated. The gross beta counting method was validated by analyzing standard urine samples. The fluctuation of the screening criteria was large, based on the time elapsed after intake. A screening criterion of 150 Bq L can be applied within 5 d after intake considering the minimum detectable activity. A standard screening criterion set to 250 Bq L will be used as an important reference for decision making and additional monitoring. Although early evaluation and accurate identification of contaminated radionuclides is preferred, these relatively simple criteria were proposed to address radiation emergency situations involving several casualties.