The UK’s Office for Nuclear Regulation (ONR) on 17 March gave EDF Energy permission for Reactors 3 and 4 at Hinkley Point B power station to return to service for a limited period of operation.
Permission for Reactor 3 will allow it to operate to a core utilisation of 17.55 terawatt days, while permission for Reactor 4 is to operate to a core utilisation of 17.3 terawatt days, which equates to two periods of approximately six months operation for each reactor. Graphite core inspections will take place between each period of operation, ONR said.
This followed an assessment that focussed on whether cracking observed in the graphite bricks that form the reactor core could compromise the key nuclear safety requirements. Specifically, these are that:
- The graphite core will not impede control rod entry, thereby ensuring that the reactors can be safely shutdown and held down, both under normal conditions and during or following fault conditions including seismic events;
- Fuel and core component cooling remains adequate both under normal operating conditions and during or following fault conditions including seismic events; and
- Fuel handling risks due to graphite core cracking remain acceptable.
ONR’s assessment included extensive scrutiny of the evidence provided by EDF “and involved extensive detailed technical discussions with EDF, with our team of specialist inspectors concluding that an adequate demonstration of safety for further operation had been provided by the licensee”.
ONR concluded: “We are satisfied that the Hinkley Point B Reactors 3 and 4 are safe to operate for the specified periods above, and that they can be safely shutdown (including in a significant seismic event) if required.” Donald Urquhart, ONRs Executive Director of Operations and Deputy Chief Inspector, said: “We are committed to ensuring the safety of workers and the Hinkley Point B site, of local residents and the wider public and we will only allow nuclear facilities in the UK to operate if we are satisfied that it is safe to do so.”
He added: “Our team of specialist inspectors have thoroughly assessed and scrutinised the evidence provided by EDF. I am satisfied that this evidence demonstrates that Reactors 3 and 4 at Hinkley Point B are able to not only operate safely, but to be shutdown safely under both normal and abnormal conditions, as may be necessary.”