03/25/2008

Chemists Try Metal Sulfide Materials to Remove Nuclear Waste

If nuclear power is to be viable in the long term, researchers must discover
how to dispose of radioactive waste. A team of Northwestern University chemists
is focusing on metal sulfide materials. Their new material is extremely
successful in removing strontium from a sodium-heavy solution, which has
concentrations similar to those in real liquid nuclear waste.

Strontium-90, a major waste component, is one of the more dangerous radioactive
fission materials created within a nuclear reactor.

The results of their research were published online in the Proceedings of the
National Academy of Sciences. By taking advantage of ion exchange, the new
method captures and concentrates strontium as a solid material, leaving clean
liquid behind. In the case of actual nuclear waste remediation, the radioactive
solid could then be dealt with separately -- handled, moved, stored or recycled
-- and the liquid disposed.

"It is a very difficult job to capture strontium in vast amounts of liquid
nuclear waste," said Mercouri G. Kanatzidis, Charles E. and Emma H. Morrison
Professor of Chemistry in the Weinberg College of Arts and Sciences and the
paper's senior author. "Sodium and calcium ions, which are nonradioactive, are
present in such enormous amounts compared to strontium that they can be
captured instead of the radioactive material, interfering with remediation."

Strontium is like a needle in a haystack: sodium ions outnumber strontium ions
by more than 1,000,000 to 1. The material developed at Northwestern -- a
layered metal sulfide made of potassium, manganese, tin, and sulfur called
KMS-1 -- attracts strontium but not sodium.

"The metal sulfide did much, much better than we expected at removing strontium
in such an excess of sodium," said Kanatzidis.

KMS-1 works in very basic and very acidic solutions, the conditions common in
nuclear waste, and everywhere in between. Metal oxides and polymer resins, the
materials currently used in nuclear waste remediation, perform reasonably well
but are more limited than KMS-1: each typically works in either basic or acidic
conditions but not both and definitely not across the pH scale.


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AplusA-online.de - Source: Environmental Protection