Materials study aims at improving nuclear reactor performance

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Corrosion of zirconium alloys in nuclear power plants - .PDF file.

Materials critical to the safe and profitable operation of nuclear reactors are to be examined by the recipient of a Royal Academy of Engineering Research Fellowship.

Dr Ben Britton, a nuclear metallurgy fellow at Imperial College London’s Department of Materials, will use the award to further the understanding of two alloys used to build reactor cladding, tubing and heat exchangers.

Britton said his particular focus will be on Inconel, which is typically used in the primary circuit, and zirconium alloys used for fuel cladding.

He said that successful fuel cladding – a hollow tube just a few millimetres thick – has to allow neutrons and heat to get out of the fuel in a high- temperature water environment of somewhere around 300o/350oC. Furthermore, zirconium is subject to residual stress due to irradiation swelling.

In 1992 the International Atomic Energy Authority noted in Corrosion of zirconium alloys in nuclear power plants that the overall costs to the US industry from materials problems could amount to as much as $10bn annually.

Britton’s area of expertise is in the systematic measurement of residual stress via measuring stress and strain within individual grains in a polycrystalline material and it is this level of accuracy that will inform new designs that will aim to avoid such cost penalties.

By analysing materials at a scale of hundreds of nanometres, Britton anticipates developing models that predict how to process these alloys and how they perform in service.

‘Some of these arguments are that if we want to make, for example, lower proliferation fuels – so that’s a lower uranium enrichment – [or] if we want to make the fuels lasts longer [then] we want to have a thinner and strong clad,’ Britton said. ‘The challenges are: how can we get greater economy from running the fuel for longer and making sure its still safe? So, its increasing the duration between refuels and also trying to make the reactor run for longer because the capital costs of a nuclear power plant are quite significant.’

Britton’s five-year fellowship will focus primarily on nuclear fission but he said his work in gaining a better understanding of a material’s fundamental properties and a more physical understanding of how stress and strain patterns emerge could be equally applicable to nuclear fusion and materials used in aerospace.