[NukeNet] Setback for safe storage of nuclear waste

[MoJo]

Setback for safe storage of nuclear waste

* 10 January 2007

* Rob Edwards
http://www.newscien tisttech. com/article/ mg19325865. 400-setback- for-safe- storage-of- nuclear-waste. html

A material that promised to lock up nuclear waste for hundreds of
thousands of years may not be up to the job.

At present high-level waste is "vitrified" by combining it with liquid
borosilicate glass and solidifying the mixture. This makes the waste safer
as it delays leakage of the radioactive material. The glass is not ideal,
though, because geological activity can break it up, so researchers are on
the lookout for more robust "immobilisation" materials.

Minerals such as zircon (ZrSiO4) are believed to have kept naturally
occurring radioactive uranium and thorium locked in the Earth's crust for
up to 4.4 billion years, surviving earthquakes and volcanic eruptions. As
a result researchers have argued that zircon, or similar synthetic
ceramics, could trap nuclear waste within their crystalline structures for
at least 241,000 years, the time plutonium-239 takes to become relatively
safe.

Now a study shows that this is unlikely. It turns out that alpha particles
released as plutonium decays knock the atoms in zircon out of position
faster than originally predicted, impairing the material's ability to
immobilise waste (Nature, vol 445, p 190).

Ian Farnan of the University of Cambridge and colleagues at the Pacific
Northwest National Laboratory in Richland, Washington, added plutonium to
zircon and used nuclear magnetic resonance spectroscopy to distinguish
between crystalline zircon and its leaky, damaged form.

The researchers found five times as many damaged zircon atoms as estimated
by computer simulations. They conclude that radioactive plutonium trapped
in zircon would start leaching out after just 210 years and lose its
crystal structure entirely after 1400 years.

The result could dash hopes for ceramics similar to zircon under
consideration in Australia, Russia and the US. Farnan believes, however,
that it is still possible to develop synthetic ceramics that don't lose
their crystalline structure as quickly as zircon. "We have demonstrated a
method that will allow us to be more confident about the storage of waste
in the future," he says.

>From issue 2586 of New Scientist magazine, 10 January 2007, page 26

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Each of the Iraqi children killed by the United States was our child. Each of the prisoners tortured in Abu Ghraib was our comrade. Each of their screams was ours. When they were humiliated, we were humiliated. The U.S. soldiers fighting in Iraq - mostly volunteers in a poverty draft from small towns and poor urban neighborhoods - are victims just as much as the Iraqis of the same horrendous process, which asks them to die for a victory that will never be theirs": Source: Arundhati Roy, "Tide? Or Ivory Snow? Public Power in the Age of Empire," 

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