Design of saltstone vaults

Radioactive wastes from processed spent nuclear fuel at the Savannah River Plant, South Carolina, are stored in underground tanks. The wastes consist of sludge and supernate. Most of the radionuclides and some non-radioactive constituents are removed from the supernate. These, along with the sludge, are converted into a glass-crystallite matrix and cast into stainless steel canisters for future disposal in a geological repository. The decontaminated supernate, also called ''salt solution,'' is mixed with cement, fly ash and a set-retarding agent and the resulting grout is transferred to reinforced concrete vaults where it sets into a monolith termed ''saltstone.'' The vaults are then capped with concrete. A total of twenty-one vaults measuring approximately 600 ft x 100 ft x 27 ft high are planned for disposal of the existing supernate plus any additional supernate generated up to year 2000. The design of saltstone vaults meets two objectives - first, it satisfies the regulatory requirements for industrial solid waste disposal sites and facilities and secondly, it ensures a safe, efficient and economical facility to operate. Various alternatives for disposal of saltstone were studied before the present concept was selected. This paper summarizes the unique features and concepts utilized to meet the design and operational objectives of a solid waste disposal facility. To our knowledge, this is a first-of-a-kind facility of this type to be built in the USA