Friday, November 6, 2009: 4:20 PM
Hereford (Camino Real Hotel)
One of the most important concerns related to the use of nuclear energy is the disposal of nuclear waste. Geologic repositories are convenient options for permanent disposal of highly radioactive waste. They are technically feasible, protect the environment in the short and long term, and allow spent fuel retrieval for future reprocessing. The repository at Yucca Mountain, Nevada, is the first geological repository intended to store high-level radioactive waste. A key factor determining the performance of this proposed repository is the release of radionuclides from the engineered barrier system into the accessible environment. In the long run, due to the physical and chemical disturbances in the environment of the repository, the waste packages will corrode at different rates and at different locations. As water penetrates the failed waste packages, the radionuclides will be carried by infiltrating water to the groundwater.
In this paper we model a failure case, where penetrations occur only on the top of the waste package and water pools inside it (bathtub). Temperature stratification of pooled water versus mixing process was examined. Our calculations show that in the case of water filling half (or less) of the waste package there will be temperature stratification of the pooled water. Conversely, for the waste package fully filled with water or above half there will be mixing in the water above the halfway point. The effect of these conditions on oxygen availability and consequently spent fuel alteration and radionuclide release will be tested.