The concentrations of90Srin water, sediment and biota at the lower region of the famous river in Saitama prefecture were determined in order to elucidate the radioecology of90Srin limnological ecosystems. 90Srconcentration in water was 2.0±0.3mBq/L (mean±standard error), and so indicated about 20 times higher than that (0.10mBq/L) of137Csin our previous report.90Srconcentrations in sediment (0.22±0.03Bq/kg), snail, Sinotaia quadratus historica (0.62±0.03Bq/kg), crayfish, Procambarus clarki (3.7±0.3Bq/kg), and crucian carp, Carassius auratus cuvieri (0.48±0.06Bq/kg), were about 110, 310, 1900 and 240 times higher than that of the water, respectively. Remarkable higher concentration for the crayfish is attributable to that (8.7±0.7Bq/kg) for the tissue of carapace weighing about 50% in comparison with that (0.33±0.05Bq/kg) for the other tissues. Difference for concentration between90Srand137Cs (in previous report) in each sample will be due to that of the concentration mechanism.
Ningyo-toge Environmental Engineering Center of Japan Nuclear Cycle Development Institute has charge of the closed uranium mines, and the measurements of the atmospheric radon concentration on and around the closed mines have been performed as part of the environmental monitoring. In order to maintain the radon monitors the practical radon reference chamber was manufactured using the natural soil containing radium. The 7.5m3radon reference chamber is cylindrical, lying horizontal, and the radon concentration can be achieved to about 1000Bq/m3, and the temperature and humidity are controllable. Since the atmospheric pressure is about 10% low because the site location is 700mabove sea level, the chamber was structurally manufactured to resist pressure of even1 atm. As a primary standard the weak radium solution is used, and gas charging type ionization chamber as a secondary standard is maintained to achieve the traceability of the radon monitors. The features of the chamber and the calibration technique are reported.