Tritium RBE estimation based on effects of chronic ingestion of tritiaed water on fetal development of mouse

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Tritium RBE estimation based on effects of chronic ingestion of tritiated water on fetal development of mouse.The anticipated increase in the tritium release into our environment from the nuclear fuel reprocessing plant and the future nuclear fusion power plant makes it important to estimate tritium RBE, especcially on the basis of long-term hazards of chronic tritium radiation exposure. In this study, therefore, an attempt was made to measure the tritium RBE based upon the inhibitory effects of chronically ingested tritiated water on fetal development of mouse.BC3F_1 female mice mated with ICR male were given drinking water containing various concentrations of tritium for whole pregnant period. At various times of the pregnant period, tritium concentration in the fetus was measured to estimate the absorbed radiation dose. The tritium concentration increased gradually from the first pregnent day to reach the plateau level at the 7 to 9th day. The estimated radiation dose increased almost linearly depending on the tritium concentration in the drinking water.The fetal body and brain weight as well as protein content of the brain tissue decreased significantly with increasing radiation dose from tritium. The dose-response curves of these tritium effects were compared with the comparable curves obtained with the chronically ^<137>Cs-gamma-irradiated fetuses, to estimate the tritium RBE. The RBE value thus obtained is fallen within the range of 1.7-1.9.