I have written before about what happened in Fukushima in March 2011, and about measuring radiation levels in Japan.  Given the situation there, a major question is: how can the contamination been cleaned up?

Removing the top 5cm

Most of the longer lasting radioactive material released was caesium-137, which is a metal that boils at a low temperature (641° C).  Large quantities of caesium vapour were released into the atmosphere, and this condensed into very fine particles, which were spread by wind and rain and deposited on over a thousand of square kilometers.  Each atom of caesium-137 is unstable, and within about 30 years, half of them will decay, releasing gamma rays.  Caesium can form salts (similar to sodium chloride, or table salt) which are absorbed into plants and by animals and humans. Continue reading →