Multi-national corporation AREVA has designed the new European Pressurised Reactor (​EPR) to meet stringent demands for increased safety and reduced cost of electricity generation. A twin EPR power station at Hinkley Point in Somerset is planned and will be constructed using modern welding technology.

The problem

AREVA has developed new welding procedures for joining materials, but before deploying them, the very high levels of qualification and validation required by the nuclear industry and regulators must be met. Together with the Open University (OU), AREVA has been using Engin-X to map residual stress in mock-ups of welded nuclear components for the purpose of validating models simulating their new processes for over five years.

The solution

The Engin-X neutron diffractometer is optimised for measuring residual stress deep within engineering components. It uses the lattice planes in crystalline materials as an atomic strain gauge. Engin-X becomes a particularly powerful tool when coupled with the Open University’s virtual laboratory SScanSS for the design and control of neutron experiments.

The role of ISIS

In the latest OU-AREVA study, Engin-X was used to study residual stresses in a large dissimilar metal weld mock-up.  AREVA has developed a new narrow gap welding procedure for joining heavy section ferritic steel components, such as a reactor vessel nozzle, to the austenitic stainless steel piping coolant system. Measurements of strain were taken along, around and through the thickness of the dissimilar metal weld mock-up at 18 locations. The results will enable AREVA to improve its numerical models and underwrite structural integrity calculations supporting the safety case for the new welding procedure.

Professor John Bouchard from the Open University led the research. He says, “This was a challenging experiment as we were working close to the operational limit of Engin-X. However the results were in good agreement with earlier measurements and validated the advanced weld prediction model developed by AREVA. We are confident that the knowledge we’ve gained will support implementation of this new welding process".

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Sara Fletcher 

Research date: July 2014

Further Information

For further information please contact Sara Fletcher