Temporal trends of 137Cs in an abandoned reactor cooling reservoir

A comprehensive resampling study was initiated for the purpose of gaining insight into 137Cs mobility and retention in Pond B, an abandoned reactor cooling reservoir at the United States Department of Energyʹs Savannah River Site in Aiken, South Carolina. Measurements made during this study were compared to those made ten years earlier. Cesium-137 inventories were estimated in water, sediment, and biotic components. The total measured 137Cs inventory in Pond B decreased from 4.6 × 1011 Bq in 1984 to 2.3 × 1011 Bq in 1994. This decline was largely driven by the decrease measured in the sediment inventory, which approximates the total inventory. The results suggest a 10-year effective half-time for 137Cs in Pond B, which is significantly more rapid than the 28-year estimate made by Whicker et al. (1990). However, it is likely that the water turnover rate between 1984 and 1994 may have been higher than the rate of 0.3 year−1 used for this estimate. Concentration ratios for the sediment and biota were very similar for both studies. A general trend of 137Cs penetration into the sediment profile and of sediment transport to deeper water was observed.