Shut Oldbury Press Release:

17 June 2007

Cautions overuled in Oldbury report

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 next year but despite cautions concerning a nuclear fire is allowed to operate for six months.

The same safety document reveals that a new safety system should be installed (2) which could take two years to fit and an automatic 'trip' system is periodically suspended (3). But despite these concerns reactor 2, which has already been closed for two years for nuclear 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 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 risk for nuclear power stations is expected to be one chance in ten thousand or higher. Nuclear Consultant John Large describes the risk as 'unacceptably high'.

Another part of the report reveals that periodic tests are being conducted at the reactor with the suspension of an automatic trip system, leaving a 'time window' during which a fuel fire could escalate to multiple fuel channels.(3)

The report predates a fire on 30th May which occurred in one of the transformers linked to the reactor, forcing it to shut down rapidly and possibly indefinitely (4). The 'trip' shut down may have caused extra damage through stress to the already heavily corroded reactor core making a future accident more likely. The explosion was heard in the village of Oldbury where a plume was seen rising from the reactor.

Nuclear consultant John Large said: "I'm disturbed by this report. If the reactor is said to be unsafe to operate for its last eighteen months then it's highly unlikely to be safe for six months."

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 months' 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."

"The oldest and most corroded reactor in the country should not be subject to this level of relaxation of standards. Despite being heavily censored, the safety report was dotted with examples of cautions being overruled. The recent generator explosion, heard in the village of Oldbury , was a warning that the unexpected can happen and we can now only guard against that by the reactor's permanent closure.

 

Jim Duffy, Shut Oldbury Campaign, Stop Hinkley, 07968 974805    

 

Note 1. "Return to service of reactor 2 following statutory outage", HSE, HM Nuclear Installations Inspectorate, May 2007

Note 2. 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 take hold in as little as thirty seconds spreading rapidly to adjacent nuclear fuel channels through cracks in the corroded reactor material. 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.

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."

 

Note 3. "Oldbury Power Station Graphite Brick Cracking, Role of the Operator" HSE Nuclear Directorate 60/07 3. 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 the station may wish to consider: ...the suspension of the automatic trip rule...[which] may have a consequential effect on the time for operator actions; the 'cliff edge' associated with the time for fault escalation to multiple channels."

JD: it appears that suspending the automatic trip function relating to the Burst Clad Detection System is permitted by the regulator. 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 one to 12 minute delay. This is periodically suspended during alarm tests. The regulator doubts the safety of this process.

 

Note 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.

 

Note 5. HSE Nuclear Directorate Assessment Report: Review of the Safety Case for the Integrity of the Reactor 2 Graphite Core, Conclusions 5.

 

Note 6. Ditto, Conclusions 6. 

 

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Revealed: faulty nuclear reactor was allowed to operate without safety alarm

By Geoffrey Lean
Environment Editor, Independent on Sunday
17 June 2007

Britain 's nuclear watchdog last month allowed a faulty nuclear reactor to start up even though it had not been fitted with an important safety system, startling internal documents seen by The Independent on Sunday reveal.

Click Here for the full story

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Page updated 28-Dec-2007