Gooey gel may help clean nuclear spills - magazine
Date: 07-Oct-99
Country: UK
Researchers at British Nuclear Fuels (BNFL) and the Idaho National
Engineering and Environmental Laboratory (INEL) in Idaho Falls have
already tested the gel in the laboratory. They will soon be putting it
to work at Britain's Sellafield nuclear processing plant.
"In the next two months it will be applied to contaminated concrete
inside a walkway near the chimney at the Windscale Pile 1 reactor, where
some of the contamination dates from a fire in 1957," the weekly science
magazine said.
The gel contains the bacterium Thiobacillus thiooxidans, which is one of
the causes of corrosion in concrete buildings and bridges.
"It feeds on sulphur-containing compounds in the concrete and converts
them into dilute sulphuric acid, which eats away at any concrete it
meets," the magazine said.
Scientists mixed the bacteria with sulphur and added a thickening agent
to give it the consistency of custard, allowing it to be spread or
sprayed on concrete.
"Humidifiers are used to keep the humidity level around the gel at about
95 percent, which allows T. thiooxidans to thrive and continue churning
out acid," the magazine added.
When the gel has done its work engineers allow it to dry, which kills
the bacteria, and then the waste is collected and disposed.
"These critters deliver the acid to precisely where you want it," said
BNFL project manager Tim Milner.
The drawback is the slowness of the process. The bacteria eats through
concrete at the rate of about one centimetre (0.4 inches) a year. But
Milner said this was not a problem because most contamination occurs in
the top few millimetres of a surface.
