Experimental reconstruction of historical WBC measuring procedure in 1986. / EKSPERYMENTAL'NE VIDNOVLENNIa PROTsEDURY PROVEDENNIa LVL VYMIRIuVAN' 1986 ROKU.

OBJECTIVE: Examination and experimental reconstruction of the historical WBC measuring procedure in 1986 and estimation of the minimum detectable activity (MDA) of those measurements. MATERIALS AND METHODS: The SRP 68 01 gamma spectrometer with attached scintillation detector based on a NaI(Tl) O 30 x 25 mm2 crystal and NC 482 ВМ one channel spectrometer (Bicron Co.) with attached scintillation detector based on a NaI(Tl) O 52 x 52 mm2 crystal were used for the study. Protective chamber of the expert type whole body counter (WBC) and homogenous human body dummy phantoms filled with dry radioactive material were applied. Results of measurements on the WBC «Screener 3M¼ were retrieved from the Radiation Registry of the NRCRM. Dosimetry and mathematical methods were applied too. RESULTS AND CONCLUSIONS: The WBC measurement procedure was reconstructed using the examples tested in 1986 to assay the level of incorporated radioactive cesium in population of contaminated territories. MDA under the WBC measurements in 1986 was found being from 1.3 kBq per human body using the NC 482 ВМ one channel spectrom eter with attached scintillation detector based on a NaI(Tl) O 52 x 52 mm2 crystal up to 7.4 kBq per human body using the SRP 68 01 gamma radiometer radiometer with attached scintillation detector based on a NaI(Tl) O 30 x 25 mm2 crystal in adults under the 60 seconds measurement time. The respective values for adolescents and chil dren were within 0.8-5.6 kBq per body and 0.5-3.8 kBq per body.

Effective doses due to external irradiation from the Chernobyl accident for different population groups of Ukraine.

A model for the external exposure of the Ukrainian population after the Chernobyl accident was developed. It is based on extensive measurements of external gamma-exposure rates (EGER) in air and of external effective doses of members of five population groups. Questionnaires were used to determine the occupancy times of members of the population groups at three types of locations; inside houses, outdoors, and outside of the home settlement. Behavior factors are defined as the ratio of individual external doses to a reference dose for a phantom standing permanently over an open field with the same average 137Cs activity per unit area as in the settlement. The behavior factors were derived for five population groups (children younger than seven years, the age group from eight to seventeen years, employees, agricultural workers, and pensioners) by two methods: first from direct measurements of individual doses by thermoluminescent dosimetry and an experimental determination of the average 137Cs activity per unit area in the settlement of interest; and second from external gamma-exposure rates in air at various types of locations and from the questionnaire data. The methods were found to be consistent and the results were used to calculate external exposures of the five population groups in the years 1987 through 1991.