In a nuclear reactor the radioactive fuel is protected from direct contact with its surrounding water by a 700 µm layer of metal alloy – an extremely thin but effective cladding. But the 2011 disaster in Fukushima revealed that this containment has its limits.
As core temperatures soared during the Japanese accident, the zirconium tubes oxidized, generated hydrogen, disintegrated and released high level radioactive fission products into the reactor vessel. Nuclear operators need disaster-proof fuel cladding materials.
The project ‘Engineered Zircaloy cladding modifications for improved accident tolerance of light water reactor (LWR) fuel’ sees researchers across the globe collaborating to search for solutions. Scientists are already advancing cladding designs by developing protective coatings on zirconium tubes with the aim to protect the metal during accident conditions.
Observational studies tell us which alloys perform best as fuel cladding ,” says Professor Michael Preuss from the Department of Materials. “But we must understand the underpinning mechanisms that define the performance if we are to advance them.”
Researchers in the Materials Performance Centre at The University of Manchester use advanced analytical tools and diffraction methods – such as electron microscopy and synchrotron x-ray diffraction – to characterise interfaces between coatings and zirconium alloys.
“Our analytical tools reveal which coatings will maintain their integrity under the demanding environments that fuel rods experience within reactor assemblies,” explains Professor Preuss. “Coatings that can survive these conditions will stand a chance of becoming integral to future fuel cladding designs.”
“Heat and corrosion resistant coatings could prevent disintegration of fuel assemblies during nuclear accidents and make nuclear power even safer than it is today,” enthuses Dr Preuss.
He hopes that novel coatings will also help to protect the cladding during normal operating conditions, giving fuel assemblies the potential to produce energy for much longer. “If advances in fuel production match advances in cladding the lifespan of fuel assemblies will be significantly extended and the production of new nuclear waste can be reduced,” concludes Professor Preuss.
By protecting cladding with advanced coatings, we aim to add longevity and safety to fuel assemblies. Longer lifespans means less nuclear waste: it is exactly what the industry is looking for.
Name: Engineered Zircaloy Cladding Modifications for Improved Accident Tolerance of light water reactor fuel
Lead researcher: Professor Michael Preuss
Department: Department of Materials
Research group: Materials Performance Centre
Dates: January 2013 – August 2016
Partners: University of Illinois, University of Michigan; University of Florida; Idaho National Laboratory and ATI Wah Chang