Preliminary concepts: materials management in an internationally safeguarded nuclear-waste geologic repository

Abstract

VI minimal. Conventional physical protection measures, directed at the sabotage threat, should be adequate. These measures are outside the scope of this report. Termination of national and international safeguards should, if possible, be carried out as far upstream in the waste cycle as possible. For all secondary wastes, termination of safeguards should be done at the waste source. However, for spent fuels, termination of safeguards at the shipping point is not possible. The necessity for repackaging spent fuel elements prior to emplacement at the repository and the current inability to verify their fissile content will require that international safeguards be maintained for those materials on an item-identification basis, at least throughout the active life of the repository, and, for national safeguards, at least until the fuel canisters are emplaced and the storage area backfilled. Any backfilled and decommissioned geologic repository, regardless of content, represents improbable national and international safeguards risks that can be addressed adequately with occasional inspections combined with environmental surveillance. Successful covert reopening of a decommissioned repository and exhumation of its contents is not a credible threat because of the magnitude of the excavation effort. More generally, this report describes three levels of materials accountability applicable to all waste materials and modes of repository operation. In order of increasing effectiveness, they are (1) item identification, (2) item identification with tamper indication, and (3) nondestructive assay. Although the repository can frequently be operated at the lowest level of safeguards, most "waste generators" will require fissile-assay capability for waste verification. In addition, waste-assay capability at the repository may be essential for process control to ensure that health, safety, and criticality criteria are honored. The technologies available to implement these three levels of materials accountability are reviewed, and recommendations are made for additional research and development. Future studies will address the problem of waste verification at the source, that is, at various types of nuclear production facilities that produce, treat, and package nuclear wastes.