Nuclear graphite has a “rosy future”

By Laura Syrett, James Sean Dickson
Published: Monday, 21 December 2015

Generation IV reactors offer fresh growth; UK leading nuclear industry development but lessons need to be learned from the past.

The nuclear graphite industry has a positive future, despite sector headwinds following the Fukushima power plant incident in Japan in 2011, delegates heard at IM’s 5th Graphite and Graphene Conference.

"The future is very rosy for nuclear graphite," Gareth Neighbour, professor and head of mechanical engineering and mathematical sciences at Oxford Brookes University, told attendees. The next, fourth generation of nuclear reactor designs (Generation IV) is currently in development, though construction is unlikely to occur until the 2030s, according to the World Nuclear Association. But a new raft of reactors with fresh design principles would lead to increased nuclear graphite production.

Nuclear graphite is made through intensive thermal and chemical processing of highly pure carbon materials, which are then pressed and baked into the shapes required by a reactor.

As well as the Fukushima meltdown in the wake of the 2011 Asian tsunami, the explosion at the graphite-moderated Chernobyl nuclear power plant in Ukraine in 1986 had also harmed the image of nuclear graphite, Neighbour said, although it did not damage the UK’s attitude to nuclear power.

Neighbour said that the UK leads the world in graphite-moderated reactors, but that the industry is being held back by a number of factors. For example, nuclear reactors are rarely built to identical specifications – rather, they are most often constructed in relatively similar "classes", each of which will have specific design differences.

With each new reactor class, a refreshed understanding of the nuclear graphite required is necessitated. The advanced gas cooled reactor class, which took over from the UK’s first generation Magnox nuclear reactor, required superior nuclear graphite grades.

"Each new graphite grade requires extremely expensive research," Neighbour said. "If we are going to develop new graphites for Generation IV reactors, we need to learn lessons from the past." Neighbour explained that nuclear graphite is manufactured in the same way as industrial graphites, with the only difference being in the purification method at the end, where impurities are removed through chlorination.

Among the standards required by nuclear grade graphite products are a density higher than 1.7g/cm3, a high degree of graphitisation, a low neutron absorption cross section, low moisture and contained air levels, and optimised strength and elastic modulus.

Sub-optimal nuclear graphite can result in differential stresses, which can lead to cracking of the graphite bricks. Neighbour advised using low impurity cokes as an input for the creation of nuclear grade graphite. Suitable cokes with optimal structure and size can contribute towards a better product, he said.