Performance assessment for low-level waste disposal facilities: Interim report

The primary differences among most low-level radioactive waste (LLR) disposal technologies are the ways in which concrete is used to construct the disposal units themselves. The BARRIER code has been developed to project the long-term performance and degradation of disposal facilities which use concrete components. BARRIER models unsaturated water flow, concrete degradation, structural failure, contaminant leaching, contaminant transport, foodchain uptake, and annual radiation doses to individuals. Radiological assessments of four disposal facilities at humid and arid sites are performed. The effects of the more aggressive chemical environment at the arid site are apparent in the times to onset of corrosion, concrete loss rates due to sulfate attack, and waste form degradation rates. These harsher conditions result in more rapid deterioration of the concrete structures. Times to the onset of cracking are typically shorter at the arid site than those at the humid site. The BARRIER methodology represents a major step toward better understanding long-term performance of alternative LLW disposal technologies. In addition to directly supplying criteria by which technologies may be compared, the BARRIER code is a valuable tool for improving the design of LLW disposal facilities. 22 refs., 14 figs., 6 tabs