ASSESSING CONSEQUENCES OF IGNEOUS ACTIVITY FOR CRITICAL FACILITIES

Location, timing, volume, and style of post-Miocene igneous activity provide a technical basis for assessing the potential for future igneous activity and associated consequences significant to the siting of nuclear/critical (critical) facilities. The work performed by the US Department of Energy (DOE) and it’s contractors for the licensing of a high level radioactive waste, geologic repository at Yucca Mountain (YM), Nevada provides an excellent case history for an approach to addressing igneous activity and associated hazards at a nuclear/critical facility. For licensing a geologic repository, the US Nuclear Regulatory Commission (NRC) specifies the requirements that must be complied with for demonstrating the performance of a critical facility that protects public health and safety. For a geologic repository, the DOE is required to assess consequences on performance of any disruptive event with a mean annual probability greater than 1 X 10^-8. In the case of YM the probability of a future igneous event intersecting a repository has been calculated. The mean value is slightly greater than that specified by the NRC. Initial consequence screening suggested that both the eruptive and intrusive components of an igneous event will disrupt repository performance. A comprehensive program was established to model and analyze the processes of intrusive and extrusive events intersecting a geologic repository to better understand impacts on performance. The abstractions of these consequence models and analyses were then used as input to assessing the overall performance of the repository using the results from a probabilistic volcanic hazard analysis. This hazard analysis for YM represents a comprehensive step by step approach to completing a full assessment of potential igneous hazards for a critical facility; however, the level of detail is not recommended for most critical facilities.