Study on the measurements and evaluation of environmental external exposure after the nuclear accident

Sakamoto, Ryuichi; Saito, Kimiaki  ; Tsutsumi, Masahiro; Nagaoka, Toshi

There are many factors which affect external exposure in contaminated area: distributions of fallout, compositions of radioactive nuclides, soil conditions, depth profile of radioactivity in soil, rain fall, snow cover, radioactive decay, shielding effects of houses and other structures, de-contamination measures, and the 'occupancy factor' which accounts for the fraction of time that inhabitants spend in different locations. In this study, several important issues concerning these factors have been investigated using field measurements and computational simulations since 1992 in the Chernobyl area. The objectives of the study were: (1) The development of a mobile survey method to collect radiation data of the contaminated area over a wide area in a short time; (2) The verification of a method to infer external doses to the population; (3) The provision of basic data used for the evaluation of external dose due to gamma ray using a Monte Carlo simulation method. (4) Characteristics of the radiation fields in contaminated area. In this report, the results were summerized.