The concentrations of 137Cs in water, sediment and biota at the lower region of the famous river in Saitama prefecture were determined in order to elucidate the radioecology of 137Cs in limnological ecosystems. 137Cs concentration in water was 0.10 mBq/l.137Cs concentrations in sediment, shellfish, Sinotaia quadratus historica (mean for 2 detectable samples), and fish, Carassius auratus cuvieri (mean for 2 detectable samples), were about 6200, 840 and 320 times higher than the concentration of the water, respectively. But 137Cs radioactivity in the crustacea, Procambarus clarki, was significantly not detected. So, 137Cs transfer mechanism in the limnological ecosystems was indicated in part.
Released activity of gaseous tritium at Tsuruga Power Station Unit No. 2 (PWR 1160 Mwe) has been measured with a moisture condensation type monitoring equipment and found to be 2 TBq per year recently. In power station, natural evaporation of spent fuel pool water has been recognized as the main source of released tritium. However, released activi-ty measured at stack has been about three times as much as estimated activity which is calculated based on concentration and evaporation volume of spent fuel pool water. This discrepancy could be explained by the presence of exchange of water between the pool and the atmosphere.