A new approach to preparing safety cases for existing nuclear plant (COSR)

BNFL is committed to achieving world class safety performance, through a process of continuously reviewing and improving its safety practices. In the mid 1990s, as part of this process, the company began to develop a new type of safety case, for existing non-reactor nuclear plants, called the continued operation safety report (COSR). Following a significant amount of development work from experts within BNFL and important contributions from its regulators, the first approved COSR was recently completed and submitted to the Nuclear Installations Inspectorate. The COSR aims to provide a visibly integrated safety and engineering case for the adequacy of continued operation of a nuclear facility. It achieves this by identifying the main plant structures, systems and components that have a safety function and provides the appropriate supporting engineering substantiation. The COSR aims to explore plant safety and identify worthwhile improvements. The document also aims to be reader-friendly by focusing on the main safety issues. It is therefore a slim safety summary which provides operators, safety specialists and regulators with an overview and introduction into the broader, more detailed safety case. This paper provides an overview of the COSR and its production process, describing the safety case improvements that have been made by comparing it to its predecessor, the fully developed safety case. The paper also illustrates the benefits of the COSR by providing current examples of its application on existing BNFL plant. Finally, the paper describes ongoing development work aimed at further improving the COSR and its production process. (author)