The commercial nuclear power industry instituted a program to protect groundwater from radionuclides released from nuclear plants in the United States (EPRI, 2008). A component of this program includes evaluation of background radionuclide concentrations in the surrounding environment and the atmospheric deposition of plant-related radionuclides. The industry subsequently issued a review of methods and tools (EPRI, 2009) and specific guidance for estimating atmospheric deposition of tritium (³H) at nuclear power plants (EPRI, 2010). These methods are used to:  estimate ³H source terms, such as nuclear power plant operations, predict resulting deposition of ³H using meteorological models, and evaluate resulting groundwater impacts using hydrogeological models.

Enhancement of radionuclide monitoring is proposed by the National Atmospheric Deposition Program (NADP) / National Trends Network (NTN) and U.S. Geological Survey (USGS). A pilot network consisting of existing NADP/NTN sites is proposed to collect monthly composited precipitation samples for ³H analysis. The network will further NADP by expanding its scope to include estimation of ³H deposition in a specified geographical area; representing a significant increase in NADP capability.   The ³H concentration and deposition data will be made freely available through web-based data dissemination, including an annual ³H deposition map for the Southeastern USA, data permitting.

Under this proposal, the pilot network will be used to test new protocols for ³H deposition monitoring.  For example, after the NADP Central Analytical Laboratory processes the weekly NTN samples into precipitation-depth weighted monthly composite samples, they will be analyzed for helium-3 (³He) by gas mass spectrometry (GMS) at the USGS Noble Gas Laboratory in Denver, Colorado.  Since ³H decays to ³He by electron capture with beta particle emission, the GMS analytical technique measures ³He to infer ³H and is capable of detection limits of 0.1 picocuries per liter (pCi/L).  GMS is commonly used to measure ³H activities for estimation of groundwater age (McMahon et al., 2013), and has been used recently to monitor ³H released from the Fukushima Dai-Ichi nuclear power plant in Japan (Povinec et al., 2013).  Samples collected at NADP NTN Site SC03, located at the Savannah River Site in South Carolina, were analyzed for ³H by GMS, but data were not available for this abstract.

EPRI, 2008, Groundwater Protection Guidelines for the Nuclear Power Plants: Public Edition, Report 101699 (http://pbadupws.nrc.gov/docs/ML0804/ML080450056.pdf), Electric Power Research Institute, Palo Alto, CA.

EPRI, 2009, Review of Methods and Tools for Estimating Atmospheric Deposition of Tritium at Nuclear Power Plants, Report 1019226, Electric Power Research Institute, Palo Alto, CA.

EPRI, 2010, Atmospheric Deposition of Tritium at Nuclear Power Plants, Report 1021183, Electric Power Research Institute, Palo Alto, CA.

McMahon, P.B., Thomas, J.C., and Hunt, A.G., 2013, Groundwater ages and mixing in the Piceance Basin natural gas province, Colorado, Environ. Sci. Technol., 2013, 47 (23), pp 13250–13257.

Povinec, P. P., Aoyama, M., Biddulph, D., Breier, R., Buesseler, K., Chang, C. C., Golser, R., Hou, X. L., Jeˇskovsk´y, M., Jull, A. J. T., Kaizer, J., Nakano, M., Nies, H., Palcsu, L., Papp, L., Pham, M. K., Steier, P., and Zhang, L. Y., 2013, Cesium, iodine and tritium in NW Pacific waters – a comparison of the Fukushima impact with global fallout, Biogeosciences, 10, 5481–5496.