A regulators viewpoint regulatory approach to judging the adequacy of nuclear safetyrelated civil engineering design

BNFL has recently started operation of its thermal oxide reprocessing plant (Thorp). Long lead times. however, mean that it is already developing options for Thorpʹs successor through its multimillion pound advanced reprocessing programme. As the future of nuclear power is uncertain, it is necessary to pursue a wide range of options, including those which involve novel technologies which are challenging to engineer but have the potential to realize substantial cost savings. Rather than employ a ʹscattergunʹ approach, engineering assessments are being carried out as early as practicable in order to eliminate candidates which are unlikely to realize sufficient cost reductions, or those which prove impractical to engineer at an industrial scale. The results of these design studies are being used to focus the main thrust of the development activities. Cost estimates including lifetime costs are continually being updated and refined as experimental data from the programme become available. Rather than construct large development rigs, the programme is also aiming to maintain flexibility by relying on the use of adaptable process and mathematical models. The use of these models allows the programme to concentrate on fundamental data which are faster and cheaper to collect. It is intended that these models, alongside the engineering and costing assessments, will form the basis of a technology demonstrator, backed up by physical demonstrators at appropriate scale where necessary to prove crucial processes. An ʹintelligent plantʹ concept is also being developed to give direction to the on-line analysis and control systems which must be developed to enable continuous plant operation. In parallel, alternative designs are being pursued at the outset to further reduce expected costs. Starting engineering assessments at this early stage has allowed the project to challenge some conventional nuclear design methodologies and produce some ʹradicalʹ design proposals for comparison. This paper will describe the development strategy in more detail and give examples of progress in these areas to date.