In-service analysis of cask contamination weeping

Spent fuel transportation casks have arrived at final destinations with removable surface contamination levels in excess of regulatory limits, although pretransport surveys indicated removable contamination levels were well below these limits. This rise in removable contamination is called weeping. Weeping, also known as sweating, is the transformation of fixed radioactive particulates on an exterior surface of a transport cask to a removable state, some time after the cask has been removed from a spent fuel pool and decontaminated. The weeping phenomenon is countered by time-consuming operational constraints and procedures which have a significant, adverse impact on cask turnaround times and occupational exposures at originating facilities. Furthermore, though not a significant health hazard, the arrival of a weeping cask results in negative public perceptions that are inconsistent with industry and regulatory goals. The objectives in resolving the technical issue of weeping are to identify specific causes of the weeping phenomenon, then to implement new cask design requirements and supporting operational procedures which will limit or inhibit the accumulation, retention, and in-transit conversion of fixed surface contamination. Benefits of finding a solution to weeping therefore include: reduced contamination of casks; improved decontamination techniques; reduced occupational exposure; and reduced cask turn-around times. Such objectives will require an understanding of the physical processes and the determination of related parameters which contribute to the weeping phenomenon. 4 refs., 6 figs., 2 tabs