An overview of the preparation of finishing Line 4 and 5. Fully developed safety case

In 1989 a fully developed Safety Case (fdSC) was prepared for the plutonium finishing facility. The facility is modern and operates largely without operator intervention. This paper gives an overview of the facility and the criticality safety assessment prepared as part of this fdSC. The potential hazards within the facility were identified by use of the HAZOP technique. Where possible the safety of the facility was demonstrated using simple hand calculations. However in a number of cases Monte Carlo computer calculations were performed to supplement this approach. In other cases it was not possible to produce deterministic arguments to demonstrate safety and for these the technique of Probabilistic Risk Assessment were used. In this way it was possible to demonstrate that the frequency of criticality within the facility was acceptably remote. (author)