Measurements of radionuclides in Pond C with an underwater HPGe detector

This study on Pond C is part of a broader effort to appraise Savannah River Site (SRS) waterways impacted by the Par Pond Dam remediation program that commenced 1991. In addition, the results were sought to provide a more complete appraisal of the status of historical radioactive releases that remain in the Lower Three Runs system. Gamma emitting radionuclide concentrations in Pond C sediment were measured with an underwater HPGe detector. The predominant radionuclide was Cs-137 and the only other radionuclide detected was Co-60, which was only 1% as intense as the Cs-137. At the time of the measurements (November 1992), the total Pond C inventory of 137Cs was 4.5 ± 0.8 Ci of which 0.30 ± 0.09 Ci was exposed during a 6-ft drawdown for Par Pond Dam repairs. The Pond C inventory of Cs-137 is only 10% of that of Par Pond, primarily because of the much larger area of Par Pond. However, Pond C has a larger average sediment concentration of 8.1 μCi/m2 compared to 4.5 μCi/m2 for Par Pond, which is consistent with Pond C being closer to the origins of the earlier SRS reactor releases. The maximum Cs-137 concentration observed for Pond C was 55 μCi/m2, which is about 10% higher than the maximum observed for Par Pond