Shut Oldbury Campaign Press Release
Expert rebuts Oldbury defence
A top independent nuclear consultant has rebutted as nonsense the regulators' comments that Oldbury's reactor cores will stay safe as long as they are not exposed to higher extremes of radiation.
On yesterday's BBC West News and documentary 'Inside Out West', a Government nuclear inspector made the claim, adding Oldbury must keep its damaged reactor core within prescribed radiation limits. But John Large has replied that it is not just high radiation levels but also high pressure inside the reactor which degrades the crucial graphite material. He also suggested that Oldbury has reached the point in time after which there is no supporting data so the nuclear safety case becomes unsubstantiated with respect to the structural performance of the weakening graphite core.
He explains "Up until this stage, the power station operator and the regulators could refer to the graphite characteristics taken from the early Harwell experimental reactors and from the older Magnox power stations, applying these characterics to the Oldbury strength and stability calculations. Now, with Oldbury progressing beyond the previous levels of graphite depletion, particularly at the higher in-core pressure at Oldbury, the safety case crucially depends upon projecting and extrapolating old data into the unknown."
He added: "The ever secretive NII seems to be now assuming a linear relationship between the graphite density and its structural performance, with the strength reducing progressively with loss of graphite mass - this is an absurd model that defies common sense in order to eke out the commercial life of this nuclear power station."
"The concern here is that not only is the graphite core in weakened state, the further degradation now being permitted by the regulator may result in a change in the structural way in which the graphite core performs as a whole. This is the 'cliff edge' situation that the regulator denies, although there is nothing in the technical papers obtained by the Shut Oldbury Campaign to demonstrate conclusively that this could not happen with potential disastrous radiological consequences. As we have seen from the New Orleans natural disaster, evacuating the nearby city of Bristol after a massive leak of radiation would be impractical before many people were radioactively contaminated."
The row has emerged following the release of Oldbury safety documents under the Freedom of Information Act to the Shut Oldbury campaign and passed on to the BBC and John Large. These show a consistent concern on the part of the Nuclear Installations Inspectorate over the safety of reactor one during its recent very prolonged inspection. Oldbury was described as the worst UK reactor in terms of the depletion of its graphite reactor core. Samples analysed in December showed the worst affected graphite bricks were depleted by over a third* of their original weight. A Manchester University engineering paper, commissioned by the NII, concluded that with 35 percent weight loss the bricks' load-bearing capacity was reduced to 15 percent of their original strength.
Out of forty four samples of the graphite material drilled out of the reactor core by remote means, exactly half were diminished by thirty percent or more. All samples showed worse than 21 percent weight loss. BNFL predicted 37 percent depletion by the end of 2005. Graphite depletion at the lower pressure Hinkley Point 'A' reactor was just 11 percent when it closed in 2000 due to steel corrosion.
Up to a month before the inspectors gave permission for the reactor to be restarted and seven months into its 'outage' or inspection, they were writing to BNFL saying they were not convinced about its safety and worried about a 'cliff-edge' scenario where the now porous graphite material might suddenly collapse or crack. But their argument suddenly petered out and permission was given with no apparent explanation of their change of position.
Movement of the bricks could lead to localised overheating and 'clad-melt' where the magnesium alloy protective covering to the uranium fuel would be destroyed.
A BNFL chief in a Nuclear Safety Committee argued that: "the extreme event is tolerable on the basis of its radiological impact". However John Large has predicted that a meltdown is possible. He said: "A fuel fire could rage for two to three days. The filters would burn out under pressure and release massive amounts of radiation.
Jim Duffy, spokesman for the Shut Oldbury campaign, said: "Oldbury chiefs say they regularly inspect the reactor. But they can't inspect all the fuel channels as it would take five years to unload the fuel. The inspectors pointed to local overheating reported in the outside areas of the reactor not covered by the minimal inspections shown in the documents. BNFL concede there may be cracks in the core. Scarily they don't know what they don't know."
ITV West will probe further the damage to Oldbury's reactor core tonight in 'West Eye View' at 7.30pm. Their editor has been told by the Nuclear Installations Inspectorate that Oldbury will now close next year, not at the end of 2008 as BNFL claim.
Jim Duffy 6 September 2005
John Large, Large & Associates:
* Worst graphite brick sample 33.8% depleted: "Oldbury Reactor 1 Weight Loss Measurements on Trepanned Graphite Samples Obtained at the 2004 Outage"