Soil samples in areas outside the 20-km exclusion zone around the Fukushima plant measured more than 1.48 million becquerels per sq. meter, the standard used for evacuating residents after the Chernobyl accident, Tomio Kawata, a fellow at the Nuclear Waste Management Organization of Japan, said in a research report published May 24 and given to the government.
Radiation from the plant has spread over 600 sq. km, according to the report. The extent of contamination shows the government must move fast to avoid the same future for the area around the Fukushima plant as Chernobyl, scientists said.
Technology has improved since the 1980s, meaning soil can be decontaminated with chemicals or by planting crops to absorb radioactive materials, allowing residents to return.
"We need to finish this treatment as quickly as possible, within three years at most," said Tetsuo Iguchi, a specialist in isotope analysis and radiation detection at Nagoya University. "If we take longer, people will give up on returning to their homes."
Soil samples showed one site about 25 km northwest of the Fukushima plant with radiation from cesium-137 exceeding 5 million becquerels per sq. meter, according to Kawata's study. Five more sites about 30 km from the plant showed radiation exceeding 1.48 million becquerels per sq. meter.
Asked to comment on the report Monday, Tepco spokesman Tetsuya Terasawa said the radiation levels are in line with those found after a nuclear bomb test, which disperses plutonium. He declined further comment.
The government introduced a mandatory exclusion zone 20 km around the plant soon after the crisis began. Kawata's study didn't include samples from inside the exclusion zone, where only government and Tepco staff may enter.
The government in April ordered the evacuation of towns including Iitate, Katsurao and Namie that are outside the 20-km zone after finding high levels of radiation.
"Basically, the way in which the current zones have been drawn up aren't a concern in terms of the impact on health," said Chief Cabinet Secretary Yukio Edano. "Using Mr. Kawata's report as a guide, we want to do what we can to improve the soil, so people can return as soon as possible."
Although the area containing soil pockets over 1.48 million becquerels per sq. meter is smaller than around Chernobyl — 600 sq. km compared with 3,100 sq. km — the level of contamination means soil needs to be cleaned or removed before residents can return, Kawata said in his report.
"It might take about one or two years for people to return to land outside the 20-km zone," the University of Nagoya's Iguchi said. "If we replace the soil, it is possible for people to return even inside the zone."
The "dead zone" around Chernobyl remains at 30 km, Mykola Kulinich, Ukraine's ambassador to Japan, said in Tokyo on April 26, the 25th anniversary of the disaster.
Belarus, which absorbed 80 percent of the fallout from the Chernobyl explosion, estimates that 2 million people, or 20 percent of the population, was affected by the Chernobyl catastrophe, while about 23 percent of the country's land was contaminated, according to a Belarus Embassy website. About a fifth of the country's agricultural land has been rendered unusable, which means some $700 million in losses each year, according to the website.
Using crops was one solution being considered by Belarus with the idea that grain harvested from contaminated areas could then be processed to make ethanol. A study funded by a philanthropy arm of Heineken NV found that radioactive elements do not transfer into ethanol and this would allow Belarus to become a major supplier to the European Union of the liquid used to dilute gasoline.
Planting crops was restarted in areas of "low-level" radiation, Michael Rietveld, chief executive officer of Ireland's Greenfield Partners, which agreed with the Belarus government in 2007 to develop an ethanol business project to decontaminate the soil, said in October 2009.
"There are cows walking over this land now," Rietveld said in reference to Belarus. "People are living over there. It's not a dangerous venture to use crops in low-contaminated areas. Most of the contamination is in the soil, not the air."
The global financial crisis hampered Greenfield's ability to raise funds and the project closed last year.
Another solution for Fukushima may be chemical treatment of the soil to allow cesium to be absorbed into porous crystals, such as zeolite, which are more visible and simpler to remove, the University of Nagoya's Iguchi said.
Restoring the land may be more critical in Japan than Belarus, where the population density is about 46 people per sq. kilometer, according to United Nations data. That's more than seven times less than in Japan, where 127.6 million people live on about 378,000 sq. km.
Restoring land use in Fukushima hinges on Tepco ending the crisis at the nuclear station, where three reactors went into meltdown.
The utility on April 17 set out a so-called road map to end the crisis in six to nine months. Tepco said it expects to achieve a sustained drop in radiation levels at the plant within three months, followed by a cold shutdown, where core reactor temperatures fall below 100 degrees.
The chance of Tepco achieving that goal is six or seven out of 10, William Ostendorff, a member of the U.S. Nuclear Regulatory Commission, told the U.S. Senate Environment and Public Works Committee.
Tepco has yet to decide how to deal with the plant site, Megumi Iwashita, a spokeswoman for the company, said last Thursday.
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