Study casts doubt on nuclear waste storage safety

LONDON, Jan 10 (Reuters) Materials that scientists had hoped would contain nuclear waste for thousands of years may not be as safe and durable as previously thought, researchers said today.

They used a technique called nuclear magnetic resonance, or NMR, which is more sensitive than other methods in detecting radiation damage.

It showed that a synthetic material called zircon encapsulating plutonium is susceptible to degradation faster than expected and may not be able to contain the waste until it becomes safe.

''Using the technique on other materials, we can confidently predict how they will behave for thousands of years into the future,'' said Ian Farnan, a materials physicist at the University of Cambridge in England.

The safe storage of nuclear waste is problematic because of the uncertainties in how materials will behave many thousands of years hence.

Farnan and scientists at the Pacific Northwest National Laboratory in Richland, Washington are trying to eliminate some of the uncertainties by measuring how rapidly the elements will damage the material they are contained in.

Their findings, reported in the journal Nature, could lead to a rethink of using zircon for the long-term storage of nuclear waste.

''We need to take this into account because most of these materials will degrade more rapidly than we had thought,'' Farnan said.

He added that the findings are particularly important for long-lived isotopes such as plutonium, uranium and neptunium.

But one way of getting around the issue may be to change the amount of radioactive waste combined into the material.

The technique, which distinguishes undamaged and radiation-damaged parts of the solid material, can also be used to screen other minerals which may be loner-lasting than zircon.

''This paper describes an exciting new approach that will enable scientists to better monitor how a material responds to radiation damage,'' said Professor Robin Grimes, of Imperial College London, in a statement.

Although the technique casts doubt on the use of zircon, Farnan believes the results are positive.

''This is good news in some respects because we will have a better understanding of these materials and how to process them before we put them down into the earth so they are not going to leak back up and harm future generations,'' he said.

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