A Proposal of Decommissioning Procedures for Bulk Facilities

Old nuclear facilities, in the final stage of their lifecycle, will move to a decommissioning phase in the near future. Under the Additional Protocol to safeguards agreements, the IAEA has a right and obligation to confirm the decommissioned status of such facilities. However, confirmation measures for these facilities have not been established and are still under discussion. The Safeguards Agreement and Additional Protocol suggest that the IAEA should confirm two conditions; the first is that all nuclear materials have been removed and the second is that all essential equipment has been taken away from the facility or dismantled and destroyed to an extent that the facility is rendered in-operable. At physical inventory taking during the operation stage, nuclear materials in bulk facilities have been recovered from the processes as practical as possible, but several quantities must be retained as residuals. These are usually represented as a negative MUF in the final material balance when the residuals will be recovered. The negative MUF could normally contribute to reduce the cumulative MUF calculated through the lifetime of the facility. However, the cumulative MUF may not be evaluated as zero due to measurement errors through the lifetime of operation, unrecoverable waste and other reasons. According to the Safeguards Agreement, a location using more than 1 ekg of nuclear material is defined as a facility and facilities with a content and throughput less than 5ekg of nuclear material are categorized as facilities that are inspected less than once a year. From this context, even if the final inventory approaches zero, the decommissioning procedure could not be completed until the cumulative MUF was less than 1 ekg. In this paper, we discuss the decision-making process for quantity requirement and determining factors for completion of decommissioning. (author)