UK Nuclear Safety Cases: Towards a Unified Approach

摘要

Risk assessments are familiar to virtually everyone in industry, and every risk assessment follows the same basic principles (i.e. identifying potential hazards, assessing the risks they pose, developing measures to control the risks, reviewing the measures periodically to ensure continued compliance and relevance). Some sectors and operations are covered by Approved Codes of Practice (ACOPs) published by the Health and Safety Executive (HSE) or by industry bodies, and these assist operating companies by setting out how systems should be designed, how operations should be performed, and what protective measures should be in place. This is an effective approach in instances where there are numerous plants or items of equipment all performing broadly similar functions and posing broadly similar hazards. Nuclear licensed sites in the United Kingdom (UK) fall within the scope of the Nuclear Installations Act, and are issued with nuclear site licences by the Office for Nuclear Regulation (ONR). A nuclear site licence carries 36 Licence Conditions (LCs) which cover everything from marking the site boundary to the disposal of nuclear waste. This paper focuses on one in particular - LC14 - which covers the safety documentation that must be in place and approved by HSE before a Site Licence Company (SLC) is allowed to operate a nuclear facility. All the different pieces of safety documentation are known collectively as 'the safety case', and despite there being more than a dozen SLCs registered in the UK, there is no ACOP for nuclear safety cases meaning that there is a range of (subtly different) sets of procedures for producing a safety case to meet LC14. In respect of Nuclear Power Plants (NPPs), all existing NPPs in the UK were built either for the United Kingdom Atomic Energy Authority (UKAEA) or the Central Electricity Generating Board (CEGB), and so effectively all had the same customer: the government. This will not be the case for the new NPPs currently being designed and starting construction. Therefore the need for an ACOP would seem to be greater than ever, to ensure consistency in the application of safety standards. Although ONR produces a specification for risk assessment and safety engineering of nuclear facilities (known as the Safety Assessment Principles or SAPs), each SLC has its own interpretation of the SAPs that informs its procedures. The aim of this paper is to strip away the differences, and by introducing the fundamental processes that underpin UK nuclear safety cases in this manner it is hoped that the paper will prompt discussion on whether there is merit in creating a safety case ACOP for the nuclear industry for the benefit of all SLCs (not just NPPs), and whether it would have the potential to centralise development of nuclear safety case processes under the auspices of HSE or potentially a body such as the Nuclear Industry Association.