Passive storage of radioactive waste

The absence of a policy for long-term management of either intermediate- or high-level waste has led to increased emphasis by both regulators and waste producers on long-term storage in regimes in which the need for human intervention is minimised. The concepts of 'passivity' of waste and its 'passive storage' have been much discussed, and their attributes defined. However, there has been a tendency to take 'passive' as an absolute, which it simply cannot be. This paper discusses passivity and passive storage, suggests definitions for relevant terms, and makes a case for a semi-quantitative index to measure the level of passivity represented by a given waste inventory. It also suggests that such an index would prove a valuable tool for judging the progress of waste treatment and decommissioning programmes. Further, increasing passivity may well reduce security concerns, and a preliminary discussion of this concept is presented.