Cracking graphite

Insights help extend life of nuclear power stations

Nuclear power stations with Magnox reactors use a loose stack of several thousand graphite bricks to slow the neutrons created by uranium fission and thereby sustain the nuclear chain reaction. This graphite core is a central component of nuclear safety and any decreases in strength are monitored.

Between 2007 and 2011 Magnox commissioned the University of Bristol to conduct programmes of research that would help improve the understanding of the degradation and fracture mechanisms of nuclear graphite. The team from the Interface Analysis Centre (IAC) at Bristol adopted advanced materials analysis techniques and could show when cores were safe for continued operation.

Bristol contributed to the total body of research that helped Magnox develop the arguments to extend the operating life of the Wylfa and Oldbury power stations. Combined, the extensions translate to an economic benefit of approximately £4.5bn.

Magnox stated "The research undertaken by the University of Bristol contributed to the necessary improved understanding of how the microstructure of reactor core graphite degrades during service and how such changes modify the associated deformation and fracture... This information, when combined with our other research programmes and detailed assessments, was used to support the arguments in the Safety Cases and provided confidence to the Regulator that Magnox was making every effort and indeed was successful in understanding holistically how this complex material (PGA graphite) performs in service. Indeed it allowed Oldbury to achieve 45 years' operation and one reactor at Wylfa continues to operate."

Read the cracking graphite case study.

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