Savannah River Site Facilities Research Articles

Legacy Contaminants in Aquatic Biota in a Stream Associated with Nuclear Weapons Material Production on the Savannah River Site.

Former nuclear weapons material production at the U.S. Department of Energy's Savannah River Site (SRS) has resulted in contamination of certain terrestrial and aquatic ecosystems on site with legacy wastes such as radiocesium (137Cs), tritium (3H), and metals. We collected fish and invertebrates from five beaver ponds (sites) above, adjacent, and downgradient of three SRS facilities (H-, F-, and C-Areas) to evaluate whether the accumulation of metals and radionuclides in biota were associated with specific facility operations and if the measured levels could pose risks to aquatic organisms. We compared concentrations of various metals, 137Cs, and 3H in fish, as well as in water (3H only), among sites along the stream gradient. Fish collected from sites adjacent to H-Area had significantly higher 137Cs concentrations compared to fish from other sites. Both biota and water samples indicated significantly greater levels of 3H in sites adjacent to and downstream of C-Area. Concentrations of zinc (Zn), copper (Cu), and mercury (Hg) in some samples exceeded effects levels reported for fish and may pose a risk to fish populations. This study reported fish tissue concentrations of 137Cs and 3H, which have not been documented extensively in ecotoxicological studies. Our results suggested that industrial operations such as nuclear material production at SRS could have long-lasting impact on the aquatic ecosystem via the release of radionuclides and metals, and long-term monitoring of physiological effects and population level impact in biota exposed to these contaminants are recommended.

Radionuclide activity concentrations in forest surface fuels at the Savannah River Site

Background/objectiveA study was undertaken at the United States Department of Energy's Savannah River Site (SRS), Aiken, South Carolina to investigate radionuclide activity concentrations in litter and duff from select areas at SRS. Litter (i.e. vegetative debris) and duff (i.e. highly decomposed vegetative debris) can often be the major fuels consumed during prescribed burns and have potential to release radiological contaminants into the environment. MethodsRepeated samples from 97 locations were collected systematically across SRS and analyzed for radionuclide activity. Radionuclide activity concentrations found in litter and duff were compared. As spatial trends were of interest, spatial distributions of radionuclide activity concentrations found in litter and duff and spatial dependency amongst the data were explored. Results7Be, 40K, and 137Cs showed statistically significant proportional differences between litter and duff samples. Duff sample concentrations for 137Cs (p < 0.0001) and 40K (p = 0.0015) were statistically higher compared to litter samples. 7Be activity concentrations were statistically higher in litter as compared to duff (p < 0.0001). For 40K litter and duff samples, spatial correlation tests were not significant at p = 0.05 and the maps did not indicate any apparent high concentrations centered near possible radionuclide sources (i.e. SRS facilities). For 7Be litter samples, significant spatial correlation was calculated (p = 0.0085). No spatial correlation was evident in the 7Be duff samples (p = 1.0000) probably due to small sample size (n = 7). 137Cs litter and duff samples showed significant spatial correlations (p < 0.0001 and p < 0.0001, respectively). ConclusionsTo date, few studies characterize radionuclide activity concentrations in litter and duff, and to our knowledge none present spatial analysis. Key findings show that across SRS, 137Cs is the primary radionuclide of concern, with the highest number of samples reported above MDC in litter (51.4%) and duff samples (83.2%). However, 137Cs litter and duff spatial trends in the maps generated from the kriging parameters do not appear to directly link the areas with higher activity concentrations with SRS facilities. The results found herein provide valuable baseline monitoring data for future studies of forest surface fuels and can be used to evaluate changes in radioactivity in surface fuels in the southeast region of the U.S.

Calibration of the HB-line active well neutron coincidence counter for measure of LANL 3013 highly enriched uranium product splits

In this paper, the setup, calibration, and testing of the F-Area Analytical Labs active well neutron coincidence counter (HV-221000-NDA-X-1-DK-AWCC-1) in SRNL are described for use in the Savannah River Site (SRS) transuranium metal production facility to enable assay of mixed uranium/plutonium metal product. The instrument was required within a three-month window for availability upon receipt of LANL uranium oxide samples into the SRS facility. Calibration of the instrument in the SRNL nuclear nondestructive assay facility in the range 10–400 g HEU is described. We also report qualification and installation of the instrument for assay of the initial suite of product samples.

Dissolution of Plutonium Metal Using Nitric Acid Solutions Containing Potassium Fluoride

The deinventory and deactivation of the Department of Energy's (DOE's) FB-Line facility at the Savannah River Site (SRS) required the disposition of approximately 2000 items from the facility's vaults. Plutonium (Pu) scraps and residues which do not meet criteria for conversion to a mixed oxide fuel will be dissolved and the solution stored for subsequent disposition. Some of the items scheduled for dissolution are composite materials containing Pu and tantalum (Ta) metals. The preferred approach for handling this material is to dissolve the Pu metal, rinse the Ta metal with water to remove residual acid, and burn the Ta metal. The use of a 4 M nitric acid (HNO3) solution containing 0.2 M potassium fluoride (KF) was initially recommended for the dissolution of approximately 500 g of Pu metal. However, prior to the use of the flowsheet in the SRS facility, a new processing plan was proposed in which the feed to the dissolver could contain up to 1250 g of Pu metal. To evaluate the use of a larger batch size and subsequent issues associated with the precipitation of plutonium-containing solids from the dissolving solution, scaled experiments were performed using Pu metal and samples of the composite material. In the initial experiment, incomplete dissolution of a Pu metal sample demonstrated that a 1250 g batch size was not feasible in the HB-Line dissolver. Approximately 45% of the Pu was solubilized in 4 h. The remaining Pu metal was converted to plutonium oxide (PuO2). Based on this work, the dissolution of 500 g of Pu metal using a 4–6 h cycle time was recommended for the HB-Line facility. Three dissolution experiments were subsequently performed using samples of the Pu/Ta composite material to demonstrate conditions which reduced the risk of precipitating a double fluoride salt containing Pu and K from the dissolving solution. In these experiments, the KF concentration was reduced from 0.2 M to either 0.15 or 0.175 M. With the use of 4 M HNO3 and a reduction in the KF concentration to 0.175 M, the dissolution of 300 g of Pu metal is expected to be essentially complete in 6 h. The dissolution of larger batch sizes would result in the formation of PuO2 solids. Incomplete dissolution of the PuO2 formed from the metal is not a solubility limitation, but can be attributed to a combination of reduced acidity and complexation of fluoride which slows the dissolution kinetics and effectively limits the mass of Pu dissolved.

Chlorine‐36 Releases from the Savanniah River Site Nuclear Fuel Reprocessing Facilities

AbstractDeterminations of 36CI (T½= 301,000 a) in waters on and near the U.S. Department of Energy's Savannah River Site (SRS) in South Carolina reveal that nuclear fuel reprocessing activities there have released measurable amounts of this radionuclide to the environment. The natural atmospheric flux of 36CI at the latitude of SRS is 20‐25 atoms m‐2 sec‐1. Atmospheric releases of 36CI from SRS, within the site boundaries, have increased this flux by a factor of at least 10 to 20. Approximately 3×109 Becquerels (Bq) [84 millicuries (mCi)] of site‐derived 36 CI have been deposited within 200 km of the plant boundaries. By comparison, fallout of 36CI from nuclear weapons testing in the 1950s deposited twice this amount of activity in the same area. Surface‐water 36CI concentrations in on‐site streams represent about 0.01 percent of the Environmental Protection Agency (EPA) drinking‐water standard and therefore pose no health concern. At SRS and similar facilities, this additional source of 36CI should prove useful for validating ground‐water and atmospheric transport models.