Green Rust Traps Radioactivity

It looks as if this trick can beapplied to a wide range of nasties to encapsulate and preserve againstrelease.  One still needs an environment thatwill prevent the influx of oxygen and that certainly exists in salt mines whosegeological stability is well known.

At least we are now informed ofan entrapment protocol that will work nicely and perhaps make removal andregeneration pretty unlikely also.  Iwould simply ensure that the green rust does form in with the material and thenencase that in the appropriate salt mine.

I am sure that sooner or later wewill 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

Copenhagen, Denmark (SPX) Mar 21, 2011

http://www.terradaily.com/reports/Green_Sludge_Can_Protect_Groundwater_From_Radioactive_Contamination_999.html

Radioactive waste decaying down at the dump needs millions of years tostabilize. The element Neptunium, a waste product from uranium reactors, couldpose an especially serious health risk should it ever seep its way intogroundwater - even 5 million years after its deposition. Now, researchers atthe University of Copenhagen have shown thehazardous waste can be captured and contained. The means? A particular kind ofgreen goop that occurs naturally in oxygen-poor water.

Bo C. Christiansen is a geochemist at the University of Copenhagenwho specializes in "green rust". In a recent article published in theprestigious journal Geochimica et Cosmochimica Acta, Christiansen describeshow green rust is able to, so to say, encapsulate and contain neptunium. It'san insight that can greatly influence how and where to dispose of radioactivewaste.

"Our study shows that even the safest encapsulation of radioactivewaste could be made safer if radioactive waste canisters are buried in a placewhere green rust will form," explains Christiansen.

For years green rust was perceived as a problem. The substance wasinvestigated primarily by material scientists who wanted to know how to avoidgreen rust formation in reinforced concrete. In recent years however, a groupof chemists, physicists andgeologists at the Department of Chemistry's Nano-Geoscience Research Group havebeen studying the substance's beneficial properties. The results have exceededall expectations.

"Neptunium is a relatively exotic problem. Not a lot of people needto safeguard a radioactive waste depot. But green rust appears to be effectiveagainst nearly any kind of pollution," says Bo Christiansen.

Green rust is a type of clay referred to as an anionic clay. Because itconsists of iron which has not entirely rusted, green rust has an electrondeficit. This makes it react very readily with other pollutants, some of whichare quite prevalent.

"A while ago we showed how green rust can react with thecarcinogenic chromium (6) and convert it to chromium (3). "Besides beingnon-toxic, chromium (3) is one of the trace elements that the human bodyneeds," says Christiansen.

Large quantities of green rust are rarely present at any givenmoment due to it's very high level of reactivity. On the other hand, it's easyto make. Green rust will form if iron sulphate and caustic soda are present inwater. But it won't last long. As soon as oxygen is added to the mix, the rustwill become ordinary red rust, known by its ochre characteristics.

Experiments demonstratinggreen rust's ability to immobilize neptunium have been conducted partly at SKB- Swedish Nuclear Fuel and Waste Management's full scale pilot researchfacility at Okskarshamn on the Swedish east coast and also in part at theKarlsruhe Institute of Technology in Germany.

Typically, radioactive waste is disposed of in iron-lined coppercanisters. 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 copperdisappears, it will only take a short time for the iron to begin rusting away.Ultimately, the radioactive waste gains entry to the groundwater. Therefore, toensure the security of radioactive waste, green rust could be established tosurround the canisters.

"Green rust is no quick-fix to clean up after pollution thatsuddenly presents itself. But our experiments have shown the surprising resultthat nature can help to clean itself. Even when the pollution is with asubstance as serious as neptunium," says Bo Christiansen who expects theresults to inform and be applied to the design and modeling of futureradioactive storage.