Investigation using the tritium tracer technique clarified that hydrogen formed by radiolysis of radiation-damaged internal reactor components and reactor coolant feedwater and hydrogen injected into reactor coolant feedwater have compatibility. Radiation-damaged Fe-Cr-Ni alloy was covered with photographic emulsion, and β-rays from tritium trapped in the radiation-damaged Fe-Cr-Ni alloy produce Ag-clusters. Energy dispersive X-ray analyzer (EDX) and transmission electron microscope (TEM) were used to confirm the presence of Ag-clusters and investigate tritium behavior. The trapping of tritium atoms in Fe-Cr-Ni alloys bombarded with Ni2+at 563 K was proved by TEM autoradiography procedure. The trapping of tritium atoms occurs at grain boundaries, voids, twins, and slip bands.
We examined the concentration of selenium and zinc in hairs, sera and feeds using a Particle Induced X-ray Emission (PIXE) analysis. In the pre-treatment of animal hair, it was shown that the radio-frequency heating (RF) ashing method using the Teflon container for tightly sealing and nitric acid is advantageous compared to the conventional wet ashing methods with Kjeldahl flask. The Se concentrations of the sera and hairs in cats were found to be higher than those in dogs (Mann-Whitney's U-test ; p<0.01, p<0.05) . In the case of dogs and cats fed the diets that have almost the same content of Se, the sera in cats were higher (p < 0.05) in Se concentration than in dogs. Therefore, we supposed that the high Se levels of tissues may be characteristics of cats. A significant correlation (r=0.71, p<0.01) between Se concentrations of canine sera and hairs was found. In cats, moreover, a significant correlation (r=0.82, p<0.05) was observed between Zn concentrations of sera and hairs. It was shown that evaluation of selenium and zinc content in serum is possible by measurement of those in animal hair.
Accumulation and excretion of137Cs in goldfish, Carassius auratus auratus, rearing in the radioactive freshwater were investigated in order to elucidate the accumulation mechanism of the radionuclide in natural living fishes. The accumulation of137Cs, expressed in concentration ratio (CR), in whole body of the fish showed a rapid increasing tendency during the rearing, and the CR value reached nearly 1 at 7th day. On the other hand, the excretion of137Cs, expressed in retention rate, in whole body rearing in non-radioactive freshwater following the accumulation above for 7 days demonstrated a gradual decreasing tendency, and the retention rate resulted in nearly 71% at 25th day. As for the tissues and organs, higher accumulation and higher excretion were found in the viscera and the gill than those in the muscle. It is so suggested that the metabolic turnover rate of this radionuclide for the viscera and the gill is more rapid than that for the muscle.
The genotoxic effects of γ-irradiation were examined using the umu-test, a bacterial short-term test for the detection of genotoxic agents. The principle of the umu-test is based on the induction of the SOS function against DNA damage in Salmonella typhimurium (TA1535/pSK1002 and TA4107/ pSK1002) ; the test measures colorimetrically the expression of umu gene involved directly in SOS mutagenesis. The strains, irradiated aerobically in phosphate buffer, showed a phasic response to γ-irradiation during their growth cycles. The SOS response was the highest level in the lag phase, suggesting that the irradiated lag-phase cells are very sensitive to γ-irradiation and survive via mutation. The hydroxyl radical scavengers, dimethylsulfoxide (DMSO) and ethanol, decreased the SOS response in a dose-related manner. DMSO (0.5 M) added into the aerobic cell suspension decreased the SOS response by about 50% in TA1535/pSK1002 and by about 40% in TA4107/pSK1002 ; the similar proportion was shown in the anaerobic cell suspension containing the scavenger. In addition, the SOS response induced under the aerobic condition was reduced by about 60% in the anaerobic cell suspension containing 0.5 M DMSO. The observations suggest that the SOS response is induced similarly by the direct excitation and the indirect effect by hydroxyl radicals generated during the γ-irradiation of aqueous solution. These results obtained using umu-test were consistent with the phasic response and the irradiation effect reported previously using the survival and DNA strand breaks of bacteria.
The characteristic peaks of 1 day period and 1 year period were obtained through the Fourier analysis of atmospheric222Rn concentration in Kobe. The222Rn concentration showed the diurnal variation and seasonal variation. The inverse relationship between the diurnal variation of the relative concentration of222Rn and atmospheric temperature was obtained, because the222Rn concentration at ground level in Kobe is affected strongly by the mixing of atmosphere. The representative times were approximately 9: 00 and 19: 00. The seasons which the highest and lowest concentration occurred in Kobe were winter and summer, respectively. The seasonal variation depended only on the contribution of the distant component. The highest222Rn concentration in Kobe was observed in winter, because the seasonal wind transports the air masses including high222Rn concentration.
The transfer of radiocesium to foodstuff of cattle is very serious, because it contributes significantly to internal exposure resulting from the intake of137Cs through the feed-cow-milk pathway. The transfer coefficient from feed to milk (Fm) is widely used to predict the dose to man from the radioactivity released to the biosphere. A commercial fuel reprocessing plant is under construction in Rokkasho-mura/Aomori Prefecture, the northeastern district of Japan. To figure out Fm under conventional farming conditions, therefore, transfer of137Cs into cattle was studied experimentally using137Cs deposited in the environment in cooperation with two daily farms in this region. Transfer factors for137Cs from feed to cow's milk have been obtained from data acquired from biweekly routine monitoring program under the two dissimilar farming conditions. The one dairy farm condition is mainly composed of high hay ration and the other is high concentrate ration. As a result of the experiments, 137Cs activity of milk correlated significantly with that of feed. The mean transfer coefficients of137Cs to milk were calculated to be 0.0037 and 0.0063 (d/l), respectively.