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 Hunterston Site Stakeholder Group (SSG) and covers activities associated with the regulation of safety at Hunterston B Nuclear Power Station. These reports are distributed quarterly and are also available on the HSE’s web site. Site Inspectors of HM Nuclear Installations Inspectorate attend SSG meetings and will respond to questions raised there by members of the SSG. Any other person wishing to inquire about matters covered by this report may contact the HSE’s Nuclear Directorate Information Centre on 0151 951 4103.
http://www.hse.gov.uk/nuclear/llc/index.htm
The site inspections carried out this quarter were primarily in connection with the three-yearly shutdown of Reactor 4 for statutory maintenance and inspection purposes.
The HMNII Site Inspector made the following planned visits during the period:
5 – 7 July;
25 – 28 July;
2 – 3 August;
and 12 – 14 September;
to undertake sample inspections of the Licensee's arrangements for controlling and completing maintenance and inspection work during the Reactor 4 outage.
Inspections are undertaken for the purpose of monitoring compliance with the conditions attached by HSE to the nuclear site licences, and other relevant provisions of the Health and Safety at Work etc Act 1974, including the Ionising Radiations Regulations 1999.
The routine inspections for this quarter, covering a range of aspects of plant operation, maintenance, and management were completed. Reactive inspection has also been carried out, with the more significant items reported below. 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.
Reactor 4/Turbine 8 was shutdown on Friday 24 th June 2005 th to carry out three yearly statutory maintenance, inspection and testing activities.
NII was satisfied that maintenance and inspection activities were completed in accordance with the Approved plant maintenance schedule; and Consent Number 502 was issued on 15 th August allowing Reactor 4 to return to service following its statutory outage.
BEGL submitted a revised Hunterston ‘B’ emergency plan for Approval, in accordance with the requirements of licence condition 11 of its nuclear site licence.
The changes made to the Hunterston ‘B’ emergency plan were essentially to reflect the recent change in licensee from BEG(UK)L to BEGL; and also the removal of the emergency response support previously provided to the Hunterston ‘A’ station.
The original Neutron Flux Pulse Count Trip Group equipment, which provided reactor protection at shutdown and start up, was installed at Hunterston B Power Station at the time of its construction and it contained components that are now obsolete and difficult to maintain.
BEGL submitted safety documentation seeking NII’s agreement to the installation of replacement Neutron Flux Pulse Count trip group equipment on Reactors 3 and 4. NII’s assessment of the safety documentation concluded that BEGL’s proposals were acceptable.
The function of the tie bar, with its end fittings, is to support the weight of the fuel stringer and lower portions of the plug unit during charging and discharging operations.
As a result of a change in the process for the manufacture of tie bars, BEGL undertook a comprehensive review of the options and concluded that the best way forward was to qualify the tiebars produced by the modified manufacturing route. As part of this process BE proposed a lead loading of up to 50 fuel stringers containing modified route tiebars into the Hinkley Point B and Hunterston B reactors.
NII was satisfied with the safety documentation that BEGL submitted in support of this proposal and our formal agreement was subsequently provided.
NII responds to non-routine events that may affect safety. As part of inspection activities at the site, we investigate safety related events that occur and follow-up those which are perceived initially to have the potential to be more significant. In particular, we examine the licensee’s response to such events. From our inspections in this quarter we were satisfied that the response by the station has been in accordance with appropriate arrangements.
There was one event rated level 1 on the International Nuclear Event Scale (INES) during the reporting period, viz.
The Reactor Shutdown Sequencing Equipment (RSSE) is initiated at the point the reactor is tripped either by operation of the main guardlines (MGL) or the diverse guardlines (DGL). In 1994 improvement work was carried out to enable the RSSE to be initiated automatically from the DGL. As part of final commissioning a required document change was not completed, consequently, routine testing of the DGL had not been carried out as part of the reactor Start-Up Tests since 1993, although the routine testing of the MGL had been carried out.
The nuclear safety significance of this event was that there was an increased risk that the RSSE would fail to initiate should the DGL be called upon to initiate the RSSE post trip; however, the safety case recognizes that the failure of the main guardlines is a very low probability event – operationally this has never occurred.
Following the statutory outage of Reactor 4 and a short, planned outage of Reactor 3 in September, the DGL tests have now been completed and these will be carried out during subsequent reactor start-ups.
On 29 July 2005, a contractor suffered fractures to bones in both of his legs during the reinstatement of shielding walls associated with the re-heater outlet penetrations.
In the site inspector’s opinion this constituted a breach of section 2 (1) of the Health and Safety at Work etc. Act 1974 and, consistent with HSE’s enforcement management model, an Improvement Notice was issued requiring the station to provide a safe system of work for this undertaking.
On a subsequent visit, the improvements that had been made to a number of shielding block restraints on Reactor 4 were inspected. The site inspector considered that the requirements of HSE’s improvement notice were met.
Under Health and Safety legislation the Site Inspector, or other HSE Inspectors, may issue formal notices to secure improvements to safety. One Improvement Notice was served during the quarter as discussed above, viz.
As part of its regulation under nuclear site licences NII issues regulatory documents, collectively termed Licence Instruments. Four Licence Instruments were issued to Hunterston B during the quarter, viz.
HM Nuclear Installations Inspectorate October 2005
St Peter’s House
Stanley Precinct
Bootle
Merseyside
L20 3LZ