It looks as if this trick can be
applied to a wide range of nasties to encapsulate and preserve against
release. One still needs an environment that
will prevent the influx of oxygen and that certainly exists in salt mines whose
geological stability is well known.
At least we are now informed of
an entrapment protocol that will work nicely and perhaps make removal and
regeneration pretty unlikely also. I
would simply ensure that the green rust does form in with the material and then
encase that in the appropriate salt mine.
I am sure that sooner or later we
will settle the problem with radioactivity.
This is certainly a good trick to take us down such a path.
Green Sludge Can Protect Groundwater From Radioactive Contamination
by Staff Writers
Radioactive waste decaying down at the dump needs millions of years to stabilize. The element Neptunium, a waste product from uranium reactors, could pose an especially serious health risk should it ever seep its way into groundwater - even 5 million years after its deposition. Now, researchers at the
Bo C. Christiansen is a geochemist at the University of Copenhagen
"Our study shows that even the safest encapsulation of radioactive
waste could be made safer if radioactive waste canisters are buried in a place
where green rust will form," explains Christiansen.
For years green rust was perceived as a problem. The substance was
investigated primarily by material scientists who wanted to know how to avoid
green rust formation in reinforced concrete. In recent years however, a group
of chemists, physicists and
geologists at the Department of Chemistry's Nano-Geoscience Research Group have
been studying the substance's beneficial properties. The results have exceeded
all expectations.
"Neptunium is a relatively exotic problem. Not a lot of people need
to safeguard a radioactive waste depot. But green rust appears to be effective
against nearly any kind of pollution," says Bo Christiansen.
Green rust is a type of clay referred to as an anionic clay. Because it
consists of iron which has not entirely rusted, green rust has an electron
deficit. This makes it react very readily with other pollutants, some of which
are quite prevalent.
"A while ago we showed how green rust can react with the
carcinogenic chromium (6) and convert it to chromium (3). "Besides being
non-toxic, chromium (3) is one of the trace elements that the human body
needs," says Christiansen.
Large quantities of green rust are rarely present at any given
moment due to it's very high level of reactivity. On the other hand, it's easy
to make. Green rust will form if iron sulphate and caustic soda are present in
water. But it won't last long. As soon as oxygen is added to the mix, the rust
will become ordinary red rust, known by its ochre characteristics.
Experiments demonstrating
green rust's ability to immobilize neptunium have been conducted partly at SKB
- Swedish Nuclear Fuel and Waste Management's full scale pilot research
facility at Okskarshamn on the Swedish east coast and also in part at the
Karlsruhe Institute of Technology in Germany.
Typically, radioactive waste is disposed of in iron-lined copper
canisters. This is suitable as long as the canisters are surrounded by water.
However, any future ice-age will draw water levels downwards.
Should the copper dry, it will begin to decay. And as the copper
disappears, it will only take a short time for the iron to begin rusting away.
Ultimately, the radioactive waste gains entry to the groundwater. Therefore, to
ensure the security of radioactive waste, green rust could be established to
surround the canisters.
"Green rust is no quick-fix to clean up after pollution that
suddenly presents itself. But our experiments have shown the surprising result
that nature can help to clean itself. Even when the pollution is with a
substance as serious as neptunium," says Bo Christiansen who expects the
results to inform and be applied to the design and modeling of future
radioactive storage.
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