Can limonite help to cut radiation?

February 19, 2013

Mount Aso limonite helps block radiation from tainted soil: researchers

http://mainichi.jp/english/english/newsselect/news/20130219p2a00m0na008000c.html

A team of researchers has succeeded in cutting radiation levels emitted from contaminated soil by sprinkling iron-rich limonite on it, paving the way for preventing external exposure without removing tainted soil.

The researchers at Tokyo University of Science and other entities announced that they have succeeded in shielding some 65 percent of gamma rays emitted from radioactive cesium in contaminated soil by putting a layer of limonite on it. If put into practice, the method will help prevent external exposure to gamma rays without the hassle of soil removal.

Limonite is mainly collected in areas around Mount Aso in Kumamoto Prefecture. The iron mineral is generated through the microbial reaction of soil deposited in the caldera of Mount Aso. Some 70 percent of limonite's main component consists of iron. The researchers focused on the fact that gamma rays do not penetrate through thick iron plates or lead.

In their experiment, the researchers laid limonite some two centimeters deep on a one-square-meter patch of farmland in Inashiki, Ibaraki Prefecture, which was contaminated with radioactive materials emitted from the Fukushima No. 1 Nuclear Power Plant in the wake of the nuclear disaster. As a result of the experiment, the airborne radiation doses on the soil surface dropped by at least 60 percent.

When experimented with soil samples from the Fukushima Prefecture village of Iitate, the researchers found that iron contained in limonite likely made it hard for gamma rays to penetrate through it after the rays bumped into the iron.