Office for Nuclear Regulation

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HSE decision on the Periodic Safety Reviews for continued operation of Hinkley Point B and Hunterston B

In January of this year we announced, via this website, that we had delayed the decision on the Hinkley Point B and Hunterston B Periodic Safety Reviews by three months. HSE's NII has now completed its independent assessment of the second Hinkley Point B and Hunterston B Periodic Safety Review undertaken by the nuclear site licensee, British Energy Generation Limited (BE).

After careful consideration NII has concluded that there is an appropriate basis for station operation whilst a PSR derived programme of work is progressed. NII has given the decision for both power stations in letters to each of the station directors and BE has put the text of these letters on its own website.

Both Hinkley Point B and Hunterston B are currently shutdown pending satisfactory resolution of issues related to the boiler tube safety case. This issue is being addressed outside the PSR programme of work. Currently NII is assessing the submissions presented by BE to demonstrate adequate safety related to the boiler tubes. Only when NII is satisfied will it grant permission for further operation of the Hinkley Point B and Hunterston B reactors.

Background

Periodic Safety Reviews (PSR) are required by the Site Licence to provide a systematic review and reassessment of the safety case, looking forwards up to ten years. NII require UK reactor licensees to carry out a PSR every ten years for each nuclear reactor site, in line with international best practice. These are significant undertakings for the licensee; and the review process may extend over a period of around 3 years.

The purpose of a PSR is to ensure that a thorough, comprehensive review is made of the basis for continued long term safe operation at regular intervals throughout a nuclear power station's life. In carrying out the review, the licensee is expected to review the total current safety case for the station and confirm its continued adequacy; to compare against current standards for new plant, evaluate any shortcomings and implement any reasonably practicable improvements to enhance plant safety; to identify any ageing process which may limit the safe life of the plant; and where necessary to revalidate the safety case until the next PSR, subject to the outcome of routine regulation.

There are always some items where uncertainty over ageing mechanisms may mean that a full case for the next ten years cannot be made. In these cases, PSR acceptance is caveated to recognise this. For AGRs, this uncertainty is, in particular, in areas of graphite integrity and in the ageing of certain steel structural features (e.g. the current problems with boiler tubes at the Hinkley Point B and Hunterston B stations). The approach is that these items are subject to more frequent inspection and forward predictions. Return from periodic shutdown for routine inspection and maintenance is only for periods of operation for which there is adequate certainty in the performance of these components. Performing an adequate periodic review is therefore a necessary basis for ten years of future operation, but is in no way sufficient. Further interactions occur as part of the permissioning process following each planned periodic shutdown. Additionally NII has powers to direct reactor shutdown at any time, should new information become available which affects the confidence in the safety operation of the plant.

As Hinkley Point B and Hunterston B are "sister" stations, with some of the PSR submissions being common, NII managed the PSR2 projects in parallel.