NUCLEAR WASTE STORAGE VAULT CLOSURE DETERMINATION

Engineers have little experience burying nuclear waste deep in 280 million-year-old salt deposits. We know that storage vaults, carved from the salt, close in on themselves and that waste placed therein will eventually be encapsulated. We do not know, however, how much time this process will require. Nor do we know the extent that temperature variations, moisture or faults evident in the walls, will affect the waste barrels or their contents. If underground, long-term nuclear waste disposal is to become widely accepted, behavior of the disturbed salt beds must be reasonably predictable. At present, the deformation mechanism is not fully understood; the research we have undertaken addresses this question. In particular, a comprehensive mathematical model and computer algorithm is being developed to predict the action of the encapsulating mechanism. Equally important, the model is being experimentally validated in situ at the Waste Isolation Pilot Plant (WIPP) site in Carlsbad, NM. Two parallel and related, but also distinct research efforts are now united. In addition to the modeling effort, experiments are being performed at the WIPP site to obtain precise values for critical model parameters. The simultaneous development of an analytical model together with comprehensive determination of the requisite boundary conditions and material and structural properties will yield an accurate working model of salt closure. The progress to date is detailed.