Evaluation of the US DOE's conceptual model of hydrothermal activity at Yucca Mountain, Nevada

摘要

A unique conceptual model describing the conductive heating of rocks in thethick unsaturated zone of Yucca Mountain, Nevada by a silicic plutonemplaced several kilometers away is accepted by the US Department ofEnergy (DOE) as an explanation of the elevated depositional temperaturesmeasured in fluid inclusions in secondary fluorite and calcite. Acceptanceof this model allowed the DOE to keep from considering hydrothermal activity in theperformance assessment of the proposed high-level nuclear waste disposalfacility.The evaluation presented in this paper shows that no computational modelingresults have yet produced a satisfactory match with the empirical benchmarkdata, specifically with age and fluid inclusion data that indicate hightemperatures (up to ca. 80 °C) in the unsaturated zone of YuccaMountain. Auxiliary sub-models complementing the DOE model, as well asobservations at a natural analog site, have also been evaluated. Summarily,the model cannot be considered as validated. Due to the lack of validation, thereliance on this model must be discontinued and the appropriateness ofdecisions which rely on this model must be re-evaluated.