New materials `could solve problem of nuclear waste’

Highly radioactive nuclear waste could be stored more safely for longer using a new type of ceramic container which can withstand being bombarded by radiation from its contents, according to researchers.

Scientists at Imperial College, London, working with research teams in the US and Japan, have identified a group of materials they believe will be able to withstand the extreme conditions of radioactive waste storage, potentially for thousands of years.

Usually high-level radioactive waste from spent nuclear fuel spends years in cooling tanks, and is then encased in boro-silicate glass and sealed in stainless steel drums. It is thought his type of storage will only work for up to 100 years.

By then the intense radiation from the waste is expected to damage the containers’ structure. The radiation’s energy knocks the atoms in the containers’ walls out of their crystalline arrangements. This will eventually make the containers appear to swell and ultimately crack, allowing the highly toxic waste to leak out.

Computer simulations by Robin Grimes and Licia Minervini at London’s Imperial College’s materials group, and laboratory testing at Los Alamos National Laboratories in the US confirmed that ceramics are better able to cope with the defects caused by radiation.

This is because ceramics have a more disordered structure in which atoms can shift their positions more easily.

Grimes said: `If this work points the way towards finding better radiation-tolerant materials and it can be successfully used to make encapsulation containers, it could be phenomenally important.’

The tests involved the compounds erbium titanate, which has a well-ordered crystalline structure, and erbium zirconate, whose structure includes positively charged ions which can move within the lattice, while keeping the structure intact.

Both materials were exposed to radioactive xenon gas to check their resistance. As predicted, the zirconate performed well. The titanate, on the other hand, was seriously weakened.

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