Health and Safety
Executive / Commission
Nuclear
LLC reports
This report is issued as part of the Health and Safety Executive's commitment to make information about inspection and regulatory activities relating to the above site available to the public. It is for distribution to members of the Hinkley Point Site Stakeholder Group and covers activities associated with the regulation of safety at Hinkley Point B Power Station. These reports are distributed quarterly and are also available on the HSE’s web site. Site Inspectors of HM Nuclear Installations Inspectorate normally attend Site Stakeholder Group meetings and will respond to any questions raised there or subsequently by members of the Site Stakeholder Group. Any other person wishing to inquire about matters covered by this report should contact the HSE, Nuclear Directorate Information Centre on 0151-951-4103.
This report will be placed on the HSE website at http://www.hse.gov.uk/nuclear/llc/index.htm.
Routine inspections continued in accordance with our annual plan. The HMNII Site Inspector made the following planned visits during the period:
Visits by other NII Inspectors also took place during this period to examine the safety case for mechanical systems and internal hazards.
During this quarter Hinkley Point B Reactor 4 spent approximately 4 weeks shutdown due to the need to carry out repairs that could not be undertaken at power.
Routine and reactive inspections have continued throughout the period to confirm that the site is operating in compliance with the conditions attached to the Nuclear Site Licence. These included inspections of Licence Conditions 7, 10, 11, 12, 15, 22, 23, 26 and 28. In general the arrangements on site were found to be satisfactory. In areas where opportunities for improvement were identified, remedial work has been agreed with station management, with the intention of achieving improvements to current station arrangements in those areas.
The NII annual review of station performance took place on 18th May 2006 and a number of actions were placed on the Station as a result, including a number of non-nuclear safety issues. The annual review of station performance against emergency arrangements took place on 20th June 2006 and progress was generally found to be satisfactory.
The management and recording of some events that occurred on the station during the period were inspected. Most of these were relatively minor and those of concern to the HMNII Site Inspector were discussed with the appropriate company staff. HMNII was generally satisfied with the actions taken.
Reactor 4 was manually tipped on 20th May 2006 due to an increase in moisture being detected in the reactor vessel. The problem was due water leakage from a boiler tube that was subsequently repaired. Reactor 4 was automatically tripped on 4th June 2006 following failure of a station electrical power transformer. Neither event posed a significant threat to nuclear safety.
On 5th July 2006 The Guardian ran a front-page story, which raises concerns over the safety of the graphite cores of the UK’s AGRs, including Hinkley Point B in the light of cracking observed in some core components. The article was partly based on a Greenpeace report, which alleges that HSE is gambling with public safety by not requiring the immediate shutdown of the affected reactors. The Greenpeace report had drawn selectively on extracts from NII assessment reports for Hinkley Point B provided in May 2006 to the Stop Hinkley Campaign under a Freedom of Information request.
All the Advanced Gas Cooled reactors (AGRs) have cores made from large numbers of interlocking graphite blocks. The bricks act as neutron moderator (i.e. they slow down the neutrons) and channel the coolant gas flow from the bottom of the core to the top over the nuclear fuel elements. Typically there are several thousand core graphite blocks making up over 300 fuel/coolant channels. Channels also run through the graphite blocks to allow the insertion of a number of control and safety shut-down rods. For various safety reasons, it is important that the graphite blocks are not excessively cracked.
Core graphite cracking is not a new or unexpected issue: it was predicted to occur late in an AGR’s life. The phenomenon was mentioned as a likely life-limiting feature in British Energy’s sale prospectus in 1996 and more recently, in the company’s 2004 listing prospectus.
During routine inspections British Energy carry out visual inspection of fuel channels using a remote camera, they measure channel and brick shapes using specially developed equipment and cut small graphite samples from the fuel channel walls to measure material properties for the graphite. British Energy have observed cracks at the brick bores of the fuel channels in the Hinkley Point B and other AGR reactor cores. HSE’s Nuclear Installations Inspectorate (NII) is monitoring closely British Energy’s work on graphite and, where necessary, is influencing the scope and extent of the reactor core inspections that the company carries out.
NII has prevented the start-up of nuclear power stations in the past until it is has been satisfied that they were safe to restart. Currently, one of the Magnox reactors at Oldbury, has been shutdown for several months because of regulatory concerns over the strength of its graphite core. NII will not allow that reactor to restart until it is satisfied with the operator’s safety case.
If NII were not confident in the safety of Hinkley Point B or any other UK nuclear reactor, it would not be allowed to operate.
Under Health and Safety legislation the Site Inspector, or other HSE Inspectors, may issue formal notices to secure improvements to safety. No such notices were issued during the reporting period.
The Inspectorate has powers under the Licence to issue Consents, Approvals and Directions. In addition the Inspectorate uses Licence Instruments to issue Specifications and Agreements under the conditions of the Licence. These are all called Licence Instruments. The following Licence Instruments were issued during the quarter:
HM Nuclear Installations Inspectorate, 14th July 2006
St Peter’s House
Stanley Precinct
Bootle
Merseyside
L20 3LZ