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Cracking in the graphite core of Advanced Gas Cooled Nuclear Reactors

Today (10am, 1 August) Reactor 3 at the Hinkley Point B nuclear power plant
will cease generation for the last time. After the closure of Reactor 4
last month, this will finally bring all electricity production at the
Somerset site to a halt.

Although there were calls for the plant to be
granted a lifetime extension, recent revelations about the extent of
graphite core cracking at Hinkley Point B have convinced the Nuclear Free
Local Authorities that EDF Energy made the right call in sticking to its
closure plan, and the NFLA fears that core cracking will increasingly
compromise the safety of Britain’s remaining aging Advanced Gas Cooled
Reactors if their operating lifetimes are further extended.

Hinkley Point B was the first plant to be equipped with two Advanced Gas Cooled Reactors
(AGRs), entering service in 1976. Over 300 fuel channels and 10 layers of
graphite bricks make up the core of each AGR. EDF Energy has described the
graphite structure as ‘the major safety requirement of the core’.

Each graphite brick is loosely connected to its neighbouring bricks by graphite
‘keys’ and there are also ‘keyways’ at the top and bottom of each
brick. The continued integrity of the structure is vital to operational
safety as it provides pathways for the fuel rods, which generate the
fission reaction, to be loaded and for the control rods, which moderate the
reaction, to be inserted.

Although overall cracking in the other AGRs is
presently reported to be under 10%, worryingly cracks in the vital keyway
bricks have been discovered at Heysham 2, Reactor 7 and at Torness, Reactor
1, which is the currently the last reactor scheduled to be closed in 2028,
suggesting a worsening situation.

NFLA 1st Aug 2022

August 1, 2022 - Posted by | safety, UK

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