CHARACTERIZATION OF TRITIUM AND STRONTIUM RELEASES AND HYDROGEOLOGY AT THE INDIAN POINT NUCLEAR POWER PLANT, BUCHANAN, NEW YORK

During excavation for the Independent Spent Fuel Storage Installation, the south wall of the IP2-Spent Fuel Pool (SFP) was exposed and two horizontal hairline shrinkage cracks were observed which exhibited signs of moisture. In addition cracks and leakage were historically identified in the Unit 1 Spent Fuel Pools (IP1-SFPs).

Following review of information concerning the construction of the facility and the hydrogeology of the area an initial conceptual model was developed which consisted of groundwater flow in bedrock governed by dominant natural anisotropies and anthropogenic influences such as blast rock fill, foundation drains, and effects of blasting on bedrock fractures. Previous studies had expected a strong southerly flow for groundwater governed by the dominant north-south anisotropies. In order to assess the leaks from the SFPs and validate our conceptual model, GZA conducted a comprehensive groundwater investigation at the Site

The results of this investigation showed the strong role anthropogenic impacts had on the natural groundwater flow regime and the more limited affect of natural anisotropies. Previous studies predicted a strong correlation of groundwater flow with bedrock anisotropies. However, the results of the investigation indicated that as a result of Site construction, groundwater flow was into the Site from the north, east and south exited the Site to the west towards the Hudson River. This was attributed to excavation of the Site to beneath the natural water table, enhanced fracture density due to blasting, and natural fracture interconnectivity with three apparent conjugate sets of fractures. A significant hydraulic gradient of approximately 0.5 occurs across the middle of the Site. Groundwater flow as well as H3 and Sr90 transport was further impacted by utility trenches and leakages from former pipe runs. Overall groundwater flow and contaminant transport was governed by the new topography created through construction and by the interconnectivity of fracture sets in the Inwood Marble. Both groundwater piezometric surfaces and contaminant mass transport showed little influence of the natural dominant anisotropies in the bedrock and would be amenable to a porous media modeling approach.