NUCLEAR WASTE STORAGE VAULT CLOSURE DETERMINATION

Engineers have little experience burying nuclear waste deep in 280 mil lion-year-old salt deposits. We know that storage vaults, carved from the salt, close in on themselves and that waste placed therein will ev entually be encapsulated. We do not know, however, how much time this process will require. Nor do we know the extent that temperature varia tions, moisture or faults evident in the walls, will affect the waste barrels or their contents. If underground, long-term nuclear waste dis posal is to become widely accepted, behavior of the disturbed salt bed s must be reasonably predictable. At present, the deformation mechanis m is not fully understood; the research we have undertaken addresses t his question. In particular, a comprehensive mathematical model and co mputer algorithm is being developed to predict the action of the encap sulating mechanism. Equally important, the model is being experimental ly validated in situ at the Waste Isolation Pilot Plant (WIPP) site in Carlsbad, NM. Two parallel and related, but also distinct research ef forts are now united. In addition to the modeling effort, experiments are being performed at the WIPP site to obtain precise values for crit ical model parameters. The simultaneous development of an analytical m odel together with comprehensive determination of the requisite bounda ry conditions and material and structural properties will yield an acc urate working model of salt closure. The progress to date is detailed.