Long-Term Assessment of Critical Radionuclides and Associated Environmental Media at the Savannah River Site

During the operational history of the Savannah River Site (SRS), many different radionuclides have been released from site facilities. However, only a relatively small number of the released radionuclides have been significant contributors to doses and risks to the public. At SRS dose and risk assessments indicate tritium oxide in air and surface water, and Cs-137 in fish and deer have been, and continue to be, the critical radionuclides and pathways. In this assessment, indepth statistical analyses of the long-term trends of tritium oxide in atmospheric and surface water releases and Cs-137 concentrations in fish and deer are provided. Correlations also are provided with 1) operational changes and improvements, 2) geopolitical events (Cold War cessation), and 3) recent environmental remediation projects and decommissioning of excess facilities. For example, environmental remediation of the F- and H-Area Seepage Basins and the Solid Waste Disposal Facility have resulted in a measurable impact on the tritium oxide flux to the onsite Fourmile Branch stream. Airborne releases of tritium oxide have been greatly affected by operational improvements and the end of the Cold War in 1991. However, the effects of SRS environmental remediation activities and ongoing tritium operations on tritium concentrations in the environment are measurable and documented in this assessment. Controlled hunts of deer and feral hogs are conducted at SRS for approximately six weeks each year. Before any harvested animal is released to a hunter, SRS personnel perform a field analysis for Cs-137 concentrations to ensure the hunter's dose does not exceed the SRS administrative game limit of 0.22 millisievert (22 mrem). However, most of the Cs-137 found in SRS onsite deer is not from site operations but is from nuclear weapons testing fallout from the 1950's and early 1960's. This legacy source term is trended in the SRS deer, and an assessment of the ''effective'' half-life of Cs-137 in deer (including the physical decay half-life and the environmental dispersion half-life) is provided. The ''creek mouth'' fisherman is the next most critical pathway at SRS. On an annual basis, three species of fish (panfish, catfish, and bass) are sampled from the mouths of the five SRS streams. Three composites of up to five fish of each species are analyzed from each sampling location. Long-term trending of the Cs-137 concentrations in fish and the subsequent doses from consumption of SRS fish is provided