A statement of nuclear incidents at nuclear installations in Britain during the first quarter of 2002 is published today by the Health and Safety Executive. It covers the period 1 January to 31 March 2002. There are two installations mentioned in the statement: Dungeness B and Heysham 1.
The statement is published under arrangements that came into effect from the first quarter of 1993, derived from the Health and Safety Commission's powers under section 11 of the Health and Safety at Work, etc. Act 1974.
1. The arrangements for reporting incidents were announced to Parliament by the Parliamentary Under Secretary of State for Energy on 30 April 1987 (Hansard col. 203-204). A minor modification to arrangements for reporting on nuclear incidents was announced in HSE press notice E108:93 of 30 June 1993.
2. Normally each incident mentioned in HSE's Quarterly Incident Statements will already have been made public by the licensee or site operator either through a press statement or by inclusion in the newsletter for the site concerned.
Statement of Nuclear Incidents at Nuclear Installations: First Quarter 2002 - single copies of each free from the Information Centre, Health and Safety Executive, Room 004, St Peter's House, Stanley Precinct, Bootle L20 3LZ.
The Health and Safety Executive presents the attached statement of nuclear incidents at nuclear installations published under the Health and Safety Commission's powers derived from section 11 of the Health and Safety at Work, etc. Act 1974.
In January 2002 BEGL reported two events that had each led to water leaks from joints in large diameter pipes of the Dungeness B Water Spray Fire System. In both cases, the system was removed from service to enable the leaks to be repaired. As the Water Spray Fire System protects safety-related equipment from fire, the reactors were shut down to maintain nuclear safety. The Nuclear Installations Inspectorate (NII) Site Inspector's initial investigation raised a number of concerns with respect to the adequacy of the Water Spray Fire System. A Direction to review and reassess safety was issued under Licence Condition 15(4). The results of this were reported to NII by the end of March 2002 as required. BEGL has already made some improvements to the system and the Site Inspector is continuing with his investigations.
British Energy reported an event at Heysham 1 on 11 March involving a fuelling machine operation at a Fuel Storage Tube. The machine had collected a new fuel assembly from the tube and had replaced this with a short shield plug. Unknown to the operators, and contrary to the indications at the fuelling machine, the shield plug had not disconnected from the machine grab. A mechanical interlock designed to prevent the machine moving until safe to do so had failed. This allowed the machine to move sideways which resulted in impact between the shield plug and the storage tube. The shield plug was severed into two parts with the lower part falling into the storage tube.
The NII Site Inspector visited the site within a few hours of the event being reported. He confirmed that the nuclear safety significance of the actual event was low, but that it could have been more serious if the fuelling machine had been operating at the reactor. There are, however, other interlocks to provide protection in this case. He also confirmed that a full investigation was underway and that the refuelling safety case would be revalidated before the machine was used again over the reactor. The event was subsequently categorised as a level 2 event (an incident) on the internationally used INES scale of nuclear events, due to the implications of multiple failures of safety provisions.
NII has closely scrutinised the licensee's investigation and
safety case revalidation process. We also used our regulatory powers
to prevent the refuelling machine being returned to service without
our agreement. We eventually allowed BE to return the machine to
service following our assessment of the revalidated safety case. We
continue to monitor the longer term actions arising from the event as
part of our routine regulatory business.