Potential Effect of Water Influx on the Dissolution Rate of UO sub 2 in Spent Fuel at the Yucca Mountain, Nevada Site

摘要

This study identifies the potential effect of groundwater influx on the dissolution rate of uranium dioxide (UO sub 2 ) from spent fuel for expected conditions at a prospective site for the disposal of radioactive waste. The analysis is based on the hydrological characteristics of the unsaturated zone at Yucca Mountain, Nevada. Although conditions that could lead to inundation of the waste packages are improbable at the site, dissolution resulting from either complete or partial exposure of the spent fuel to water was considered. Estimates were made of the lower limit of water-contact time with the UO sub 2 in spent fuel under partially saturated conditions. If spent fuel is inundated, the dissolution rate of the UO sub 2 is constrained by its solubility limit. If partially saturated conditions exist, the uraniun dioxide leach rate could control the dissolution process. Under conditions of both partial or complete saturation, the dissolution rate of uranium is shown to be a linear function of the water influx. The practical application of the results of this study for determining radionuclide-release rates from spent fuel is also discussed. (ERA citation 11:011559)