ABSTRACT
The paper assesses unplanned operational events at the Sellafield nuclear installation, formerly Windscale and Calder Works, in Cumbria, England, over the period 1950-2000 that had, or could have had, radiological implications for members of the general public. A unified system of off-site impact rating has been developed using a site-specific application of the International Nuclear Event Scale (INES) that is applied retrospectively to events since the start of operations at the site in 1950. Published and unpublished sources of information have been used to assemble what the authors believe to be a complete list of events over the period that would now be assessed as INES level 3 or above on the basis of off-site impact. The last such event occurred in 1984. The exercise also demonstrates that it is possible to apply the current INES rating scheme to a wide variety of radiological events.