Long-term isolation of high-level radioactive waste in salt repositories containing brine

Description/Abstract

At present, only one concept, the Swedish design utilizing a thick-walled copper waste package, has been accepted as being capable of isolating high-level waste for hundreds of thousands of years in a granite-type repository. Theoretical arguments show that after the relatively short times required for salt consolidation self-shielded thin-walled copper waste packages have no significant failure or degradation reactions in anoxic neutral and acid brines. Thermodynamic analysis of reactions after consolidation (constant-volume reactions under lithostatic pressures in the absence of oxygen) show that miniscule amounts of metal reacting with brine can produce very large hydrogen pressures. Analyses of gamma radiolysis and diffusion processes show that in an array of thousands of waste packages removal of hydrogen from the outer packages should be negligible for a properly selected salt repository.