Management and Operational Control of Criticality

The evidence of the six process criticality accidents that have been reported to date shows that, without exception, they have been due to the failure of operational controls. In no instance has a criticality accident in processing been due to the use of wrong data 01 inaccurate calculation. Criticality accidents are least likely to occur in the production stream and are more likely to be associated with ancillary equipment and operations. Important as correct criticality calculations are, there are many other considerations which require the exercise of judgement in establishing the operational environment. No operation involving fissile material should be permitted without a formal review resulting in a documented statement of (a) the environmental assessment, (b) the nuclear safety arguments which demonstrate safety under that environment, and (c) the operational requirements which will ensure the validity of (b) under the conditions of (a). To ensure the continued viability of the environmental assessment and the continued reliability of clearance conditions there should be close supervision by operating management, and periodic checks made by site nuclear safety staff. Additionally, there should be periodic and systematic examinations by competent persons who are not responsible to the overall management of the site. (author)