The influence of the facility nuclear safety case on the design of naval refit support equipment

Continuous review, adaptation and improvement through upkeep and maintenance periods has enabled the Royal Navy submarine fleet to remain fit for purpose through successive life extension programmes. Devonport Royal Dockyard, Plymouth, provides nuclear submarine dry dock facilities for maintenance. The Site Licences which authorise operations of these nuclear facilities are administered by the Office for Nuclear Regulation which ensures that the intent of the facility nuclear safety case is maintained throughout all operations. As such, any dock modifications and refit support equipment or structures must be designed within the framework of the safety case.
A requirement to undertake refit activities external to the hull of a nuclear submarine while in dock resulted in a design and build project for a temporary dock-bottom building to provide a safe and capable environment. The design of this building’s structure and sub-systems was heavily influenced by the nuclear safety case.
This paper explores the challenges of designing equipment within the constraints of the nuclear licensed site, identifies the provenance and the requirements of the nuclear safety case of a dry dock nuclear facility, and examines the influence of this safety case upon requirements management, and the design lifecycle. The design of the dock-bottom building is presented, including an outline of the technical challenges which arose, and some of the novel solutions developed, including; a modular, seismically- qualified, primary structure; and a modified crane incorporating a crushable element. The paper explores the issues of finite element analysis of the primary structure to substantiate performance and satisfy the safety case. The paper also presents a discussion of the influence and impact of the safety case upon the building design project.