• November 20, 2015


Cracks have been found in graphite bricks which line the reactor core at the Hunterston B nuclear power station in Ayrshire.

EDF which operate the plant say the fault was detected during routine maintenance. They say:

“The level of cracking which is considered reasonable is far below anything which would affect the reactor’s safe operation.

“It is accepted by our regulators and materials experts that cracks will occur in some of the bricks and that the core will lose some of its mass as part of the normal ageing process.”

When I wrote on behalf of the Celtic League to the HSE in 2006 about cracking of the graphite core in UK nuclear reactors they said:

“As with all structural components graphite will change with time. For a gas cooled reactor it was recognised this may result in some graphite cracking during its operational life. Therefore to ensure that plant, equipment and materials continue to meet their safety function the Nuclear Site Licence requires licensees to carry out
routine inspection, examination, monitoring and testing of these components. For graphite NII requires the licensee to have in place on line monitoring arrangements, inspection programmes, and material testing regimes.

“The licensees consider information from these activities in their routine reviews of the safety case for continued operation. The safety case for continued operation is then submitted to NII for its consideration. If NII were not satisfied with the safety case it would not allow a reactor to continue to operate. A typical example of reactor shutdown due to a satisfactory case on graphite not being made is Oldbury Reactor
I and 2.”

Interestingly in the same letter they gave a shutdown date of February 2011 for Hunterston B.

In the same correspondence I asked about cracking of the graphite bricks in the Heysham nuclear plant just across from Mann in Lancashire. Strangely in this case the HSE were not willing to be very open saying they were ‘closed documents’ (see extract below);

“Limited graphite brick cracking has been found at Heysham, but none at Wylfa. NII has reviewed the safety case for Heysham and is satisfied reactor operation should continue. Reports regarding the limited graphite brick cracking at Heysham have been produced but these are closed documents.”

In 2009 I pressed the HSE again (the Chief Inspector of Nuclear Installations) this time are queries were specific to both Heysham and Hunterston power plants:

The Chief Inspector told me:

“The possibility of cracks developing in the cores of Advanced Gas-cooled Reactor (AGR) graphite moderator bricks has been recognised and predicted for many years and extensive work undertaken to understand the degradation mechanisms and to mitigate associated safety implications. Around 2001 unpredicted cracks were detected during routine core inspection. More recently a so-called double-cracked brick (a graphite brick with two full-height axial cracks), again not predicted, was found during core inspection at Hartlepool Power Station. Such brick defectiveness is of greater safety significance due to its potential to affect the core keying system. This latter observation gave rise to the article you refer to in the New Scientist in March 2005.”

Note the comment “brick defectiveness is of greater safety significance due to its potential to affect the core keying system”.

So are Britain’s nuclear plants operating in some instances well beyond there sell-by date safe – or are they quite literally cracking up?
Issued by: The Celtic News



The Celtic League established in 1961 has branches in the six Celtic Countries. It promotes cooperation between the countries and campaigns on a range of political, cultural and environmental matters. It highlights human rights abuse, military activity and socio-economic issues


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