Clean sweep

The threat of escalating terrorist attacks is behind a new system for cleaning radioactive materials from porous services.

Developed by Michael Kaminski and colleagues from the US Department of Energy's Argonne National Laboratory, the technique would remove the residues from so-called 'dirty' radiological bombs from bricks and concrete, making it unnecessary to demolish contaminated buildings and monuments.

'If a radioactive device were activated in public, the primary concern would be widespread contamination,' says Kaminski, from Argonne's chemical engineering division. 'This contamination is particularly hard to remove in buildings made from brick and concrete, where the pores, or holes, in those materials make it easy for radioactive materials to become trapped.'

Kaminski's solution combines nanotechnology with techniques familiar from household items such as disposable nappies. In a three-stage process, the porous surface is first sprayed with a surfactant-containing wetting agent and a super-absorbent gel, which also contains engineered nanoparticles which can bind chemically to the radioactive elements.

The wetting agent causes the radioactive material to detach from the interior of the pores in the material and resuspend themselves in the liquid phase, which is then drawn into the superabsorbent gel. Once inside the gel matrix, the radioactive materials become attached to the nanoparticles. The gel can then be vacuumed off the wall, and the radioactive particles removed for safe disposal.

The system originated as a clean-up technique designed for the nuclear industry, says Kaminski.

'Within our group, we are combining our experience from the past several years in areas of nuclear power plant decontamination, engineered nanoparticles and polymer gels to develop this new decontamination technology,' he says.

'Right now, it is common practice to demolish the contaminated materials in the hope of getting rid of the radioactivity. Our technique would allow the surfaces to be preserved, which means we wouldn't have to deface monuments or buildings just to remove the radiation.'