Abstract
The background γ-ray intensity and chemical composition of soil was determined in the Naka terrace of Tokai-mura Village and Hitachinaka City, where many nuclear facilities are located. The aim of the sampling was to assess environmental radiation within the Naka terrace and the sites of nuclear facilities. The study was initiated following the JCO Criticality Accident on September 30 th, 1999. γ-ray measurement and soil sampling were conducted at the nodes of a 500 m grid. The γ-ray intensity recorded at all sample points is less than the average radiation of Japanese granites and less than the typical radiation of humans as assessed by UNSCREA. The chemical characteristics of the soil are divided into 3 types. The distribution of both the soil types and background γ-ray intensity is controlled by geographical and geological factors. K2O and Rb concentrations within the soil show a good correlation with background γ-ray intensity. Our observations indicate that environmental radiation within the study area is derived principally from natural radioisotope radiation.
