Cooperative research at JAERI on the consequences of the Chernobyl accident. 1. Study on the measurements and evaluation of environmental external exposure after the nuclear accident

Measurement data obtained from 1992 mainly in 30 km distant areas from the accident reactor were analyzed and evaluated. On-site study included the radiation survey studies of wide range of areas with the spherical NaI(Tl) detector carried on the car and helicopter, studies on the accumulated dose in inhabitants and dose rate distribution of their residential settlements with the glass dosimeter and portable gamma dose-rate meter, experimental studies on the shielding effect of houses by simulation and studies on the characterization of environmental γ-ray field. These studies brought about developments of the method for rapid radiation survey in wide range of contaminated areas, of the evaluation method for estimated external exposure dose in residents, of the Monte Carlo arrangement method for evaluation of γ-ray doses and of analytical method for contaminated areas. Data were provided to organizations for measures of Ukraine and Belarus and would be also useful for possible urgent matters in future. (K.H.)