The Health and Safety Executive has published its summary report of the Periodic Safety Reviews (PSRs) of the UKs first two commercial Advanced Gas-Cooled Reactor nuclear power stations. This report gives a more detailed account of the decision of HSEs Nuclear Installations Inspectorate (NII), announced in January 1997, to allow these power stations to continue to operate beyond their 20th year.
The two stations, Hinkley Point "B" in Somerset, and Hunterston "B" in Ayrshire are owned and operated by Nuclear Electric Ltd. (NEL) and Scottish Nuclear Ltd. (SNL) respectively (the licensees) which are both subsidiaries of British Energy plc. The PSRs are a continuation of a series of safety reviews of UK nuclear power reactors that are carried out on a 10 year frequency in line with international practice. Topics addressed by these reviews include reactor safety systems, reactor pressure boundary and internals, operating history and the treatment of hazards such as earthquake and fire. Other topics addressed include refuelling and waste management, plant ageing, human factors and radiation doses.
An initial report summarising the NII assessment findings for the PSRs for the two power stations was issued as a technical annex to a press statement in January 1997. That gave NIIs overall conclusions on the acceptability for continued operation beyond 20 years. This report provides a more detailed discussion of NIIs main findings. In the meantime, some requirements have been cleared, further information submitted for consideration and programmes of ongoing work agreed. Under a condition attached to the nuclear site licence, PSRs are required to be carried out by the licensee of a nuclear power plant. The reviews are complementary to the day-to-day regulatory controls which are applied to nuclear power stations. They provide the opportunity to undertake a comprehensive study of the safety of the plant, taking into account aspects such as its operational history, ageing factors which could lead to a deterioration in safety, and the advances in safety standards since the time of construction. From this, the safety of future operation of the plant can be evaluated. The reviews are submitted to the NII for its consideration and assessment to evaluate whether an adequate level of safety has been achieved.
NII is satisfied that the licensees have completed a detailed scrutiny of the safety of the two nuclear power stations. Improvements to the plant which both licensees initiated in advance of the reviews have enhanced the safety of both stations, bringing the designs closer to modern standards. The overall outcome of the licensees' reviews, together with the programmes of additional modifications and inspections which have been put in place, provides confidence in the ability of these stations to continue to operate safely.
Nevertheless, NII has also identified the need for some further work, over and above that proposed by the licensees. These requirements have been set out in additional work programmes which NII has agreed with NEL and SNL. Subject to the completion of this work, and continuing satisfactory results from the routine inspection, monitoring and demonstrations of safety required under the nuclear site licensing arrangements, NII has expressed itself confident that the Hinkley Point 'B' and Hunterston 'B' nuclear power stations can continue to operate safely until they are 30 years old. At that time a further PSR will be required.
Hinkley Point B and Hunterston B nuclear power stations : the findings of NII's assessment of Nuclear Electric's and Scottish Nuclear's periodic safety reviews.
A full copy of this report can be obtained free of charge from HSE Books at PO Box 1999, Sudbury, Suffolk, CO10 6FS, United Kingdom, tel. (+44) 01787 881165, fax. 01787 313995.
Hinkley Point B is on the North coast of Somerset, some 13 km NW of Bridgwater and was commissioned in 1976. It was originally owned and operated by the Central Electricity Generating Board. On privatisation of the Electricity Supply Industry in 1990, Hinkley Point B together with all the CEGBs nuclear assets were transferred to Nuclear Electric plc, remaining in goverment hands until 1996, then together with the other NEplc AGR power stations, it was transferred to Nuclear Electric Ltd, a subsidiary of British Energy plc which was privatised later the same year.
Hunterston B is on the West coast of Ayrshire some 40 km west of Glasgow and was also commissioned in 1976. It was originally owned and operated by the South of Scotland Electricity Board (SSEB) and together with SSEBs other nuclear power station at Torness was formed into Scottish Nuclear Ltd in 1990. SNL also remained in government hands until 1996 when it too became a subsidiary of British Energy prior to the privatisation of the latter.
The Advanced Gas-Cooled design reactors (AGRs) are unique to the UK and are based on an extension of the earlier Magnox reactor design. Seven twin reactor stations were constructed on sites in England and Scotland in the 1970s and 1980s. Hinkley Point B and Hunterston B have the longest operating history of the AGRs and are thus the first to undergo a PSR. Similar reviews on the other AGR stations are in progress to an agreed programme with completion of the Dungeness B review due in early 1998.
PSRs are an internationally recognised arrangement for reviewing the safety of nuclear power stations on a regular (usually 10 yearly) basis. The next PSR for Hinkley Point B and Hunterston B will be due for completion at the end of 2006. The equivalent reviews which were carried out on earlier UK reactors were known as the Long Term Safety Reviews, the last of which was completed in 1995.
The principal design features of the Advanced Gas-Cooled Reactor are a pre-stressed concrete pressure vessel, enriched uranium fuel in a ceramic form which is contained within stainless steel clad pins in a graphite core, all cooled by high pressure carbon dioxide gas.
This page was written 30th June 1997