State of Nevada review of Phase 1 of the INTRAVAL Project

The INTRAVAL Project which started in October, 1987, was designed to be an international cooperation project and is managed by the Swedish Nuclear Power Inspectorate. The project was to undertake the issue of what constitutes a validated model in terms of repository performance assessment. The US Nuclear Regulatory Commission (NRC) in 10CFR60.21 requires an explanation of measures used to support the models utilized in the assessment of performance which are included in the License Application. The NRC Nureg 0856, ''Final Technical Position on Documentation of Computer Codes for High Level Waste Management'' defines the term validation to be, ''assurance that a model as embodied in a computer code is a correct representation of the process or system for which it is intended. The notion of validating that a code accurately represents the operational physical processes at a given site has turned out to be a very difficult endeavor. Especially for sites such as Yucca Mountain where the flow regime is poorly known. There is currently no mathematical description of unsaturated flow in fractured -- porous media which the majority of the scientific community can support with confidence. Further, all overall performance calculations performed to date by the US DOE assume one dimensional porous flow which enters through the top of Yucca Mountain and makes it way to and through the repository. Not surprisingly these types of calculations lead to the conclusion that little or no release is possible via the groundwater pathway. Quite naturally, the State of Nevada is concerned with these types of calculations, preferring to see something more realistic in terms of conceptual models, fracture pathways, and releases. This concern is carried into the INTRAVAL process because if the DOE is to validate a model of flow at Yucca Mountain within INTRAVAL, the model must be realistic