Resilience improvements to UK nuclear power plants

Following the events at Fukushima, the Office for Nuclear Regulation (ONR), the UK nuclear safety regulator, undertook a series of reviews into the resilience of UK nuclear power plants to severe events. These reviews highlighted a number of areas in relation to electrical infrastructure where it considered licensees should review their arrangements, considering both onsite and offsite infrastructure as well as the ability to recover following a complete loss of site infrastructure. In response, UK licensees have been exploring four parallel approaches to improving the resilience for each of their sites. Firstly, through modifications on-site such as enhancements to the installed diesel generators and related systems. Secondly through improvements to the resilience of essential instrumentation to Station Black Out events. Thirdly, through the provision of off-site backup equipment that can be deployed to any site following a severe event. Finally, the provision of event qualified connection points on site to enable timely restoration of long term essential electrical supplies and cooling to key systems. This last item gives a central focus to the issues of switchboard availability and the resilience of the whole network to large potentially common cause internal and external hazards. This paper will discuss the electrically related findings of the ONR reviews, explore the reasoning behind those decisions, and describe the approaches being taken by UK licensees. (authors)