Families plant rice the old-fashioned way just outside the 20-kilometre exclusion zone in Futaba District, Fukushima Prefecture (13 May 2012). Image Source: Mainichi Shinbun.
After today's earlier post, I'd had enough of Fukushima for awhile, but it's the gift that keeps on giving (German readers may appreciate the pun). The blogger at EX-SKF picked up a news story from today's issue of the Mainichi Shinbun (translation here), about families who have volunteered to disprove fears of radioactive fallout. They are planting experimental crops of rice the old-fashioned way, just outside the Fukushima Daiichi power plant's 20-kilometre (approx. 12.5 mile) exclusion zone. The rice farm is in Kawauchi-mura; the continuation of farming there is part of an "experiment ... to develop new sales routes for the rice grown in Kawauchi-mura. The project is called 'Revival of Rice Project (復活の米プロジェクト).'"
The location of the farm is marked in the map below (which the EX-SKF blogger took from the Kobe Shinbun); the map includes fallout data, based on Japanese government measurements. The fallout in the area last year (October 2011) averaged 100K to 300K Bq/m2 of radioactive cesium.
You can see a more recent map (November 2011) with a discussion of what level of radiocesium fallout is considered 'safe' in the soil, with that level defined, at the BBC here:
On converting Bq/kg to Bq/m2 (not K Bq/m2 as cited above), see here, and this explanation: "There are methods that can give us estimated conversion between Bq/kg and Bq/m2. Mr. Tetsuji Imanaka at Kyoto University uses a method of multiplying 20 to amount of Bq/kg to have estimated Bq/m2 amount whiles the Japanese Nuclear Safety Commission indicated a method of multiplying 65 to amount of Bq/kg." EX-SKF: "It doesn't seem like the 'safe' enough level for a mother to let her small daughter go bare feet and hands to play in the mud." An environmental disaster, atomic science, and engineering errors now intersect with normally-admirable national stoicism (for a debate on that attitude, see comments beneath this article) and folly.A quantity of radioactive material has an activity of 1Bq if one nucleus decays per second - and 1kBq if 1,000 nuclei decay per second. ... An international research team investigated this area late last year and concluded: "The team found that the area of eastern Fukushima had levels of the radioactive element that exceeded official government limits for arable land. Under Japanese Food Sanitation Law, 5,000 becquerel per kg (Bq/kg) of caesium is considered the safe limit in soil (caesium-137 makes up about half of total radioactive caesium, and therefore its safe limit is 2,500 Bq/kg). The researchers estimate that caesium-137 levels close to the nuclear plant were eight times the safety limit, while neighbouring regions were just under this cut off; the rest of Japan was well below (averaging about 25 Bq/kg) the safety limit. ... A second study, published in the same edition of PNAS, collected over a hundred soil samples from within 70km [approx. 43.5 miles] of the Fukishima plant, and found similarly high caesium-137 levels across the Fukishima prefecture, and its neighbouring regions.
Read all my posts on Nuclear topics.