Criticality safety administration in legacy waste management - 14613

Canadian Nuclear Laboratories (CNL) is Canada's largest nuclear science and technology laboratory, with a long history in developing and progressing in the field of nuclear science. In the early years of nuclear science and technology development, there were practices used for nuclear material storage and management that have led to recent challenges in meeting current regulatory (Canadian Nuclear Safety Commission) safety requirements. There are over 900 storage locations where significant amounts of experimental fuel and operations fuel are stored, with varying degrees of administrative rigor being applied over the last 60+ years. To determine the safety of the stored materials, it was impracticable to examine every location to determine the status of fissile material composition. A risk graded approach was developed to first administratively determine the locations that were at risk, followed by comparison to upper subcritical limits. This narrowed the area of concern from >900 locations to approximately >70 locations. Locations of concern were then modeled with more accurate geometry, reflection and moderation conditions to further narrow down the selection area. This further narrowed the locations of concern to 32. Reducing overall risk, this small selection of locations have been selected for non-destructive imaging/examination and further analysis to confirm geometry to ensure criticality safety in all the storage locations. (authors)