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 th e Chernobyl accident was developed. It is based on extensive measureme nts of external gamma-exposure rates (EGER) in air and of external eff ective doses of members of five population groups. Questionnaires were used to determine the occupancy times of members of the population gr oups 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 p ermanently over an open field with the same average Cs-137 activity pe r unit area as in the settlement. The behavior factors were derived fo r five population groups (children younger than seven years, the age g roup from eight to seventeen years, employees, agricultural workers, a nd pensioners) by two methods: first from direct measurements of indiv idual doses by thermoluminescent dosimetry and an experimental determi nation of the average Cs-137 activity per unit area in the settlement of interest; and second from external gamma-exposure rates in air at v arious types of locations and from the questionnaire data. The methods were found to be consistent and the results were used to calculate ex ternal exposures of the five population groups in the years 1987 throu gh 1991.