Shut Oldbury Press Release:
04 June 2007
New report shows regulators' concerns over Oldbury
An internal report (1) revealed under the Freedom of Information Act shows that a nuclear reactor at Oldbury is unsafe to operate through to its planned closure date of December 2008.
The same safety document reveals that an automatic 'trip' system has been suspended (2) and a new safety system should be installed (3) which could take two years to fit. But despite these concerns reactor 2, which has already been closed for two years for safety reasons, was still recently allowed to restart on a temporary basis till November this year when a new safety case must be made.
The report predates a fire on Wednesday which occured in one of the transformers linked to the reactor, forcing it to shut down, possibly indefinitely (4).
The graphite reactor core is at the centre of concerns by the regulator who states: "Due to uncertainties relating to: measurement of [graphite] density; prediction of weight loss; and predictions of structural integrity I am currently unable to recommend operation to the planned end-of-generation." (5)
The statement goes on to allow a short term restart till this November on the judgement that the risk of a nuclear fuel fire or 'clad-melt' for the period is one chance in a thousand (6). Clad-melt risks for nuclear power stations are normally one chance in ten thousand or higher.
Jim Duffy spokesman for the Shut Oldbury campaign said: "The documents reveal on one hand that Oldbury is essentially finished, as required safety work is impossible, but on the other hand that the regulators have astonishingly relaxed their stance to let it splutter on for a few more weeks' worth of electricity. There is a serious question here as to whether the regulators have allowed an economic argument to slip into what should be a pure safety case."
"We will be asking for more detailed data on how on earth restarting Oldbury was considered acceptable, but now the public are evidently at a greater risk as the operators and regulators have relaxed what should be a more stringent safety case."
Jim Duffy' Shut Oldbury Campaign, Stop Hinkley, 07968 974805
(1) "Return to service of reactor 2 following statutory outage", HSE, HM Nuclear Installations Inspectorate, May 2007
(2) "Oldbury Power Station Graphite Brick Cracking, Role of the Operator" HSE Nuclear Directorate 60/07: Conclusions and Recommendations: "For the 'majority' case the claimed human reliability has been demonstrated. For the 'exception' cases I cannot support a reliabilty claim of the operators. Therefore station may wish to consider: ...the suspension of the automatic trip rule...[which] may have a consequential effect on the time for operator actions."
JD: it appears that the automatic trip function relating to the Burst Clad Detection System has been suspended. The BCD System would normally trigger an automatic shut-down of the reactor in the event of a nuclear fuel fire, detected by loose fission particles in a general area of the reactor, although with a potentially devastating 12 minute delay. This may have been suspended as nuclear particles from earlier fuel damage are circulating around the cooling system and would trigger the shut-down. So this is now apparantly being left to the discretion of the operator. The regulator doubts the safety of this process.
(3) HSE Nuclear Safety Directorate Assessment Report: a Revised Safety Case for the integrity of the Graphite Cores to the Planned End of Generation: Proposal for Return to Service of Reactor 2 (NP/SC 4927): Recommendations: 37 ."[NII] should continue to press for the installation of the Failed Fuel Trip System as a potential ALARP option to improve safety at the station."
JD: The Failed Fuel Trip System differs from the Burst Clad Detection System and has the advantage it could trip the reactor automatically much earlier in the event of a fuel fire in just one fuel channel. A fuel fire could escalate in as little as thirty seconds spreading to adjacent nuclear fuel channels. The Magnox magnesium cladding can burn in as little as 700 degrees C even in the carbon dioxide cooling gas.
A nuclear expert suggests this safety system could take two years to fit.
(4) BBC News 24 report: 2nd June 2007:
Nuclear power plant stays closed
Oldbury Power Station in South Gloucestershire is not expected to reopen in the foreseeable future, a British Nuclear Group spokesman said.
An inquiry has been set up to look into the overheating at the plant, which led to the fire in an electricity transformer on 30 May.
No-one was injured in the fire, but the facility cannot return to normal until the inquiry reports.
The fire broke out on the non-nuclear side of the plant.
(5) HSE Nuclear Directorate Assessment Report: Review of the Safety Case for the Integrity of the Reactor 2 Graphite Core, Conclusions 5.
(6) Ditto, Conclusions 6