Remobilization of 137Cs in the steel creek system following L-reactor restart at the Savannah River Plant

The L Reactor at the Savannah River Plant (SRP), which had been shut down in 1968, was restarted in November 1985. As part of the environmental impact statement required to restart the reactor, SRP agreed to monitor 137Cs transport in Steel Creek, which receives the cooling water discharged from the L Reactor. A comprehensive sampling and analysis program to monitor 137Cs transport from Steel Creek to the Savannah River prior to and following L-Reactor restart was initiated. Results from the first month's study showed that most of the remobilized 137Cs came from the stream portion of Steel Creek and that concentrations at the mouth of Steel Creek were less than in the stream portion. No extensive sediment transport of 137Cs to the Savannah River occurred. Extrapolating the first month's 137Cs transport data for a year, < 2 Ci of 137Cs will have been transported to the Savannah River during the first year of L-Reactor operation. This is ∼ 50% of the initial estimate that was made for the L-Reactor environmental impact statement showing that the methods used in the initial estimate provided conservatism in assessing the transport of 137Cs to the Savannah River. These 2 Ci of 137Cs transported to the Savannah River when diluted with the annual flow of the river would result in a concentration of ∼ 0.3 pCi/l or < 1% of the proposed EPA drinking water guide of 100 pCi/l