SREL Reprint #2202

Effects of a partial drawdown on the dynamics of 137Cs in an abandoned reactor cooling reservoir

F.W. Whicker, T.G. Hinton, and D.J. Niquette

Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA

Abstract: The effects of a partial drawdown on 137Cs dynamics in an abandoned nuclear reactor cooling reservoir, Par Pond at the Savannah River Site in South Carolina, USA, were examined. The drawdown, which occurred in 1991, caused major ecosystem changes, exposed 5.3 km2 of contaminated sediments, and led to hydrological changes that altered the limnology of the reservoir. Measurements of 137Cs in sediments, largemouth bass (Micropterus salmoides), and aquatic plants were begun at the time of the drawdown and the status of these studies is reported. Cesium-137 concentrations in large-mouth bass muscle have increased steadily since the drawdown. The most likely cause is the decreased potassium concentrations in water resulting from a change in the primary water source for Par Pond. Decreased body condition of the bass as well as a greater average 137Cs concentration in sediments in contact with the water column may also be contributing to the 137Cs trend in the fish. Sedimentation rates and water turbidity were increased after the drawdown due to erosion processes, but the natural colonization of the littoral zone and lake bed by plants has reduced these problems. Preliminary data on 137Cs in vegetation indicate higher but more variable concentrations in plants on the lake bed as compared to littoral zone macrophytes

SREL Reprint #2202

Whicker, F.W., T.G. Hinton, and D.J. Niquette. 1997. Effects of a partial drawdown on the dynamics of 137Cs in an abandoned reactor cooling reservoir. Freshwater and Estuarine Radioecology: 193-202.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).