Five types of ionization chamber survey meters and a type of GM counter survey meter were calibrated for measuring the β-ray absorbed dose rate due to a skin contamination, using natural uranium, 198Au and 204Tl circular sources. To estimate the β-ray absorbed dose rate of a contaminated skin, measurements were done twice by a survey meter without and with a filter, keeping the distance from the contaminated skin surface to the survey meter at 10mm. The absorbed dose rate was obtained by multiplying a net reading (a difference between a reading of survey meter's indicator measured without the filter and a reading measured with the filter) by a multiplying factor. Multiplying factors varied approximately in proportional to the inverse square of source diameter when the source diameter was smaller than the detector's diameter, and approached gradually to a constant value as the value of source diameter increased over the detector's diameter. The multiplying factors of each ionization chamber survey meter were equal to one another within ±30% independently of type (manufacturer) and the maximum energies of sources. The multiplying factors of GM counter survey meter to 204Tl and 198Au sources were three times as large as those to natural uranium sources. The change in the multiplying factor was less than ±20%, when the measuring distance was 10±2mm.
A new method of waste treatment of animal carcass contaminated with plutonium was proposed. A multi-step process was designed and tested at a laboratory scale which was composed of the following processes; microwave dehydration, heat decomposition and ashing. Microwave dehydration was found the most adequate as the first step of the treatment because of the negligible release of nonvolatile radioactivity. About 70% of body weight was reduced by microwave dehydration. Dehydrated animal carcass was decomposed by graded electric heating under anaerobic condition. Burnable gas and vapour produced by the heat decomposition were oxidized by passing through a reheating tube with excess air. The exhaust gas had no significant radioactivity. The residue of charred carcass was oxidized by heating with excess air. The weight of final product was up to 8% of original wet weight. The proposed multi-step process provided to be adequate for the waste disporsal of Pu contaminated animal carcass.
Concentrations of 90Sr and 137Cs in an airborne dust at altitudes of 10km and 6km were measured. Samples were collected on filter paper with the dust sampler mounted on an aircraft over the northern, middle and western parts of Japan, during the period between October in 1972 and September in 1975. And the following results were obtained; 1. The concentration of 90Sr and 137Cs changes in a seasonal variation showing a tendency of increase from October, reaches its maximum from February to April, decreases gradually afterwards reaching its minimum from July to September. 2. The regional distribution for the nuclides tends to be high in the northern parts and low in the western parts. 3. There is about 1/10 difference in the value of each concentration between the altitudes of 10km and 6km.
Measurements of the radioactivity and the analysis of nuclides in a fresh airborne dusts have been made for Chinese nuclear explosion test during 1972-1974. Samples were collected on filter paper with a dust sampler mounted on an aircraft at high altitude over Japan. It was observed that the airborne dusts reached Japan in 1-3 days after the bursts, and its effect is temporary in most cases. The level of the gross beta-activity of fresh airborne dusts increase after tests, but the concentrations of 90Sr and 137Cs do not very markedly.
A computer code, designated GAMMA-CLOUD, has been developed by specialists of electric power companies to meet requests from the companies to have a unified means of calculating annual external doses from routine releases of radioactive gaseous effluents from nuclear power plants, based on the Japan Atomic Energy Commission's guides for environmental dose evaluation. GAMMA-CLOUD is written in FORTRAN language and its required capacity is less than 100 kilobytes. The average γ-exposure at an observation point can be calculated within a few minutes with comparable precision to other existing codes.