EDF Energy has been in discussion with the Office for Nuclear Regulation (ONR) to agree the return to service of Reactor 3 at Hunterston B following the completion of a recent inspection programme. The inspections confirmed the expected presence of new keyway root cracks in the reactor core and also identified these happening at a slightly higher rate than modelled.

EDF Energy has today decided that, while Hunterston B Reactor 3 could return to operation from the current outage, it will remain offline while the company works with the regulator to ensure that the longer term safety case reflects the findings of the recent inspections and includes the results obtained from other analysis and modelling. The operation of other reactors is not affected.

We have been working over many years to fully understand and prepare for these late life changes to the reactor core and regular inspections at all our plants have provided a clear understanding of how the reactor cores age. The longer term safety case will build on work already completed and EDF Energy expects that this will demonstrate that there are large safety margins both now and for the projected reactor lifetime.

Over £100m has been spent on the graphite research programme which benefits from the expertise of our own team of specialists as well as academics at several leading U.K. universities.

During this time EDF Energy may take the opportunity to carry out additional planned routine maintenance.

We expect the unit to return to service before the end of 2018. This will result in a reduction in 2018 nuclear output forecast of up to 3TWh.