This paper seeks to provide a simple summary of the design justification of the major Sellafield process plants and management strategies in a form that those unfamiliar with this history can readily digest. The objective is to provide evidence that the current Sellafield "production" plant flowsheets were well conceived, remain fit for purpose, that over their remaining operational life the safety and environmental performance will be acceptable and, given the limited duration of this remaining production, that the pattern of Sellafield site discharges from these plants will align with the broad principles agreed by the UK Government at OSPAR (the Oslo Paris convention).

Examination of the options evaluation and process justification of a number of existing major Sellafield production plants demonstrates that when establishing the preferred flowsheet, in all cases, human safety and environmental protection were evaluated in depth. For all Sellafield plants, work was undertaken as part of the design development to demonstrate that chosen process options represented the best option and, had a formal BPEO submission been required at the time, the work done would have fully-supported this submission.

The safety and environmental performance of the Sellafield process plants is good and risks to people or the environment are small. Existing process flowsheets remain fully-fit for the task of delivering the limited remaining production throughput. It has been shown, however, that considerable progress and real advances in environmental protection can be achieved by a focus on continued delivery of Best Practicable Means in the operation of the Sellafield production plants during their remaining lifetime.