HSE's NII has now completed its assessment of the second Periodic Safety Review of Heysham 2 and Torness Power Stations undertaken by the nuclear site licensee, British Energy Generation Limited (BE).
After careful consideration NII has concluded there is an appropriate basis for station operation whilst the programme of further work identified by the review is progressed. NII has given the decision in letters to each of the Station Directors.
The Decision Letter affirms that NIIs view is that the periodic review is not considered complete and adequate until this work programme is satisfactorily completed, and confirms NIIs intention to monitor BEs progress in discharging the work. However, should the work be discharged to adequate quality it is unlikely that NII would require BE to submit a further PSR for these stations until such time as BEs own arrangements require (currently January 2019 for an NII Decision Date of January 2020).
Periodic Safety Reviews (PSRs) 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 and is repeated 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. PSR acceptance is caveated to recognise this. For AGRs, the most important of these uncertainties are in areas of graphite integrity and in the ageing of certain structural features. These items are subject to more frequent inspection and forward predictions. Operation between periodic shutdowns for inspection of such features is only for periods 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 continued maintenance, inspection, and testing are also required to justify continued operation. Adequacy of the ongoing safety case is considered by NII 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 Heysham 2 and Torness are "sister" stations, many of the PSR submissions were common to both. NII managed the PSR2 projects in parallel. There are minor differences in the agreed Action Plans but similar Decision Letters were sent to each Station Director.
NII will produce a project overview report explaining the decision and the programme of work in greater detail.