Assessment of fuel designs for new commercial nuclear reactors within the United Kingdom

The United Kingdom has recently started a process of licensing a new set of commercial nuclear reactor sites. This has not happened for twenty years and since that time, the industry has changed significantly. Previously, nuclear plants were built by a single government-owned body and individual sites were licensed by a government inspectorate. The licensing practices have developed as a response to requirements, as detailed in this paper and changes have taken place in consultation between the power generating body and the licensing authority. This established relationship no longer exists. Potential power station sites are now owned by international utilities and designs are offered by reactor (and fuel) vendors from numerous countries. Before the utilities commit themselves to a particular vendor design, they need to be confident that the design can be licensed in the United Kingdom. Both vendors and utilities are no longer necessarily familiar with United Kingdom licensing practices and principles and therefore the licensing authority has developed a pre-licensing design assessment process, in consultation with vendors, to provide confidence that UK requirements can be met. The purpose of this paper is to illustrate the principles used within the United Kingdom to consider the suitability of safety cases supporting the licensing of operations at nuclear facilities. The application of these assessment principles to fuel designs is illustrated by considering some issues addressed during the recent Generic Design Assessment of the proposed fuel designs. The United Kingdom safety case requirements fall broadly into two categories; a need to set operating rules, in the form of limits and conditions of operation, and a need to demonstrate that risks have been reduced to a level 'As Low As Reasonably Practical'. These requirements are explained in this paper. The issues used to illustrate the approach adopted by ONR include: the basis for protecting fuel against Pellet-clad Interaction; and the rational for the assessment against fuel limits in reactivity and loss-of coolant accidents. (authors)