ESTIMATION OF RADIATION DOSES TO POPULATION GROUPS IN THE BRYANSK AREA FOLLOWING THE CHERNOBYL ACCIDENT

摘要

Since 1990, a joint Russian-Nordic project has been carried out to determine the absorbed doses to selected population groups in the Bryansk region of Russia. The measurement programme involved a total of about 500 persons, living in six different villages, with contamination levels ranging from 0.8 to 2.3 MBq ~(137)Cs/m~2. Most of the villages were decontaminated to various degrees, and some villages were not decontaminated. Each September of the years 1990-1994, measurements of individual external doses were carried out using thermoluminescence dosimeters. Since 1991, individual urine samples have been collected annually from about 150 persons and have been used for estimating the body burden of ~(137)Cs and the internal dose contribution. Adults working outdoors and indoors, and groups of school children were included in the study. Dose measurements using anthropomorphic phantoms were performed in order to determine the relationship between several parameters that are important for determining the external dose in contaminated areas. The reduction of the Chernobyl component of the external dose was 10-30% per year in the period from September 1990 to September 1994. The most heavily contaminated villages were most effectively decontaminated and the effect of this decontamination is reflected in the dose data. The results also reflect the differences between doses to people with indoor occupations and doses to people with outdoor occupations, as well as the differences between doses to persons living in wooden houses and doses to persons living in brick houses. Individuals with indoor occupations received a lower effective dose from external irradiation than those with outdoor occupations. The doses to people living in brick houses were lower than those to people living in wooden houses. The levels of ~(137)Cs in urine decreased somewhat between 1991 and 1992, but during 1993 they increased, which is probably due to a larger consumption of locally produced and wild growing food.