Geochemistry Model Validation Report: Material Degradation and Release Model

The purpose of the material degradation and release (MDR) model is to predict the fate of the waste package materials, specifically the retention or mobilization of the radionuclides and the neutron-absorbing material as a function of time after the breach of a waste package during the 10,000 years after repository closure. The output of this model is used directly to assess the potential for a criticality event inside the waste package due to the retention of the radionuclides combined with a loss of the neutron-absorbing material. The output of this model is also used by the external accumulation model to assess the potential for accumulation of radionuclides outside the waste package. The scope of this report is to describe the development and validation of the MDR model and to use the model to analyze the degradation of commercial spent nuclear fuel (CSNF) waste packages and codisposal waste packages containing high-level waste glass (HLWG) and U.S. Department of Energy (DOE) spent nuclear fuel. This report was developed in accordance with Technical Work Plan for: In-Package Geochemistry for Criticality Evaluations (SNL 2006 [DIRS 179452]) requirements.