Radioactive cesium blankets 8% of Japan’s land area
Some 8 percent of Japan’s land area, or more than 30,000 square kilometers, has been contaminated with radioactive cesium from the crippled Fukushima No. 1 nuclear power plant.
Spanning 13 prefectures, the affected area has accumulated more than 10,000 becquerels of cesium 134 and 137 per square meter, according to the science ministry.
The ministry has released the latest version of its cesium contamination map, covering 18 prefectures.
Radioactive plumes from the Fukushima No. 1 plant reached no farther than the border between Gunma and Nagano prefectures in the west and southern Iwate Prefecture in the north.
Ministry officials said the plumes flowed mainly via four routes between March 14 and 22 after the plant was damaged by the Great East Japan Earthquake and tsunami on March 11.
The first plume headed westward from late March 14 to early March 15, when huge amounts of radioactive materials were released following a meltdown at the No. 2 reactor.
It moved clockwise over a wide area in the Kanto region. Radioactive materials fell with rain and snow, particularly in the northern parts of Tochigi and Gunma prefectures.
A branch of the plume moved southward from Gunma Prefecture, passing through western Saitama Prefecture, eastern Nagano Prefecture and western Tokyo.
It stopped in western Kanagawa Prefecture, where the Tanzawa mountain range rises up.
The second plume headed northwest in the afternoon of March 15, heavily contaminating parts of Namie and other municipalities in Fukushima Prefecture.
The third plume headed northward, apparently in the afternoon of March 20.
Areas in northern Miyagi Prefecture and southern Iwate Prefecture were probably contaminated when it rained between the late afternoon of March 20 and early March 21.
The fourth plume headed southward from the night of March 21 and early March 22.
It passed through northern Chiba Prefecture but largely skirted central Tokyo due to a pressure pattern, limiting contamination in Tokyo and Kanagawa Prefecture.
It is believed that the amount of radioactive materials released from the Fukushima No. 1 plant increased between March 20 and 23, but the reasons are not yet known.
In Fukushima and seven other prefectures, 11,600 square kilometers, or 3 percent of Japan’s land area, have annual additional radiation levels of at least 1 millisievert, according to Environment Ministry estimates.
The government has said it will remove radioactive materials if annual additional radiation levels reach 1 millisievert or more.
The science ministry has been carrying out aerial monitoring of radioactive materials since April.
Helicopters fly at relatively low speeds, allowing monitoring of levels of radiation released from the ground at a height of 1 meter.
Cesium accumulations in soil and radiation levels are also measured separately at selected sites on the ground.
Officials estimate cesium accumulations at other locations using correlations between radiation levels 1 meter above the ground monitored from helicopters and the actual cesium accumulations at the selected sites.
Cesium 137 will have a long-term impact on the environment because it has a half-life of 30 years.
It was detected even before the Fukushima accident, apparently as a result of nuclear testing conducted by other nations.
Still, the maximum amount found in nationwide surveys since fiscal 1999 was 4,700 becquerels in Nagano Prefecture.
The science ministry’s cesium contamination map excludes the effects of pre-disaster contamination.
The map will cover 22 prefectures when it is completed by the end of the year. Data for Aomori, Ishikawa, Fukui and Aichi prefectures will be added.
HIROSHI ISHIZUKA, Asahi Shimbun Staff Writer, November 21, 2011
http://ajw.asahi.com/article/0311disaster/fukushima/AJ201111210014
Most radioactive cesium piled up within 2 centimeters of soil surface
Most of the radioactive cesium emitted by the crippled Fukushima No. 1 Nuclear Power Plant has piled up within two centimeters of the soil surface, the government has announced.
The Cabinet Office’s Team in Charge of the Lives of Disaster Victims announced on Nov. 16 the detailed results of its survey on cesium dosage and accumulations in the soil, forests, buildings, rivers and other environments. Based on the results, the Cabinet Office has concluded that “most of the cesium can be removed if the top two centimeters of the soil is scraped away from its surface.”
The survey, conducted between July and September, covered the Fukushima Prefecture town of Tomioka, which is designated as a no-go zone, and the town of Namie, which has both a no-go zone and an evacuation preparation zone. Officials said 80 to 97 percent of cesium detected in those areas’ schools, parks, rice paddies and other locations was found within two centimeters of the soil surface.
In forests and orchards, cesium tended to penetrate deeper into the soil, but 68 to 88 percent of cesium still accumulated within two centimeters of the topsoil, according to the survey.
In the leaves of deciduous trees that have grown following the onset of the nuclear disaster in March, 60 to 26,000 becquerels of cesium per kilogram was detected, while the leaves of evergreen trees that have existed since before the March 11 disasters contained levels of cesium about 10 times higher than that, at 18,000 to 220,000 becquerels per kilogram. Meanwhile, fruits of trees that have grown in places with high cesium concentrations in the soil hardly bore cesium, the survey has found.
Mainichi Shimbun , November 17, 2011
Fukushima radiation meters fail gov’t accuracy requirements
Radiation meters installed at parks and primary schools across Fukushima Prefecture do not meet the central government’s minimum accuracy requirements, it was learned on Nov. 18.
The Ministry of Education, Culture, Sports, Science and Technology cancelled its contract with the meters’ supplier the same day. The ministry will begin removing the 600 devices soon, and reopen bidding on the radiation meter contract. The meters were scheduled to start operating in October, but that has now been pushed back to February next year at the earliest.
According to the ministry, five firms bid on the meter supply contract in July, won by Tokyo-based telecommunications equipment firm Alpha Tsushin K.K. for some 370 million yen. The contract requirements demanded that radiation measurements be accurate to within plus or minus 20 percent, but soon after they were installed in October the ministry discovered the meter readings were off by as much as 40 percent.
The science ministry intends to demand compensation from Alpha Tsushin for breach of contract.
Mainichi Shmbun , November 19, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/11/19/20111119p2a00m0na007000c.html
Mountains limited spread of fallout from Fukushima
NEW YORK (AP) — A map of radioactive contamination across Japan from the Fukushima power plant disaster confirms high levels in eastern and northeastern areas but finds much lower levels in the western part of the country, thanks to mountain ranges, researchers say
The mountains sheltered northwestern and western parts of Japan as radioactive cesium-137 emerged from the power plant and blew downwind, the scientists said.
Cesium-137 is just one of the radioactive materials that came out of the plant, but researchers focused on that because it’s particularly worrisome. It lasts for decades in soils, emitting radiation and potentially contaminating crops and other agricultural products.
The research, published online Monday by the Proceedings of the National Academy of Sciences, shows estimated levels of contamination. It did not investigate implications for health.
The researchers, from Japan, Norway and the United States, said the levels they estimated would severely restrict food production in eastern Fukushima Prefecture and hinder agriculture in neighboring provinces. That outcome is already recognized in Japan, where regulators monitor food products from those areas for contamination before they are cleared for shipment.
The Fukushima Dai-ichi plant, 140 miles (225 kilometers) northeast of Tokyo, was heavily damaged in March when it was swamped by a tsunami triggered by an earthquake.
A second report, from a separate group of Japanese scientists, investigated levels of radioactive cesium, iodine and tellurium on the surface in east-central Japan. Such materials are airborne after a nuclear accident and fall to the ground when it rains. While the power plant incident began on March 11, the study linked ground contamination in the Fukushima prefecture to a March 15 rainfall, and contamination in Tokyo and some other areas to a March 21 rain.
Soil contamination in Tokyo has already made officials ban shipment of tea leaves grown there, and some elementary schools in Tokyo and nearby have taken decontamination steps like removing topsoil. In addition, there is growing concern about radioactive “hotspots” found in Tokyo and elsewhere outside Fukushima. The Japanese government has taken responsibility for decontamination.
Associated Press, November 15, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/11/15/20111115p2g00m0dm015000c.html
Fukushima Pref. to begin research on forest decontamination
FUKUSHIMA (Kyodo) — Fukushima Prefecture will start studying ways to decontaminate forests tainted by radioactive materials from the crisis-hit nuclear power plant in the prefecture, local officials said.
Aiming to find effective methods to clean up forests near residential areas, the prefecture’s research center will soon conduct experimental felling in the evacuation preparation area outside the 20-km no-entry zone from the Fukushima Daiichi power station.
Fukushima Prefectural Forestry Research Center will monitor how radiation levels change by removing fallen leaves, trimming low branches and felling trees in the first-ever decontamination experiment of its kind, according to research center officials.
The experiment will take place at forests in the town of Kawamata where up to six microsieverts per hour of radiation have been detected about one meter above the ground, the officials said.
The government-set annual allowable dose of radiation is 20 millisieverts a year.
Kyodo Press, November 19, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/11/19/20111119p2g00m0dm011000c.html
Gov’t to lower Fukushima plant workers’ maximum radiation exposure
TOKYO (Kyodo) — Health minister Yoko Komiyama said Monday the government will restore to the normal level the maximum dosage of radiation to which workers at the Fukushima Daiichi nuclear power plant can be allowed to be exposed after the crippled facility reaches a stable state of cold shutdown within this year as planned by the government.
At present, workers trying to stabilize the nuclear complex are to cease work after being exposed to 100 millisieverts of radiation since March under rules devised in the emergency situation. The plant was hit by the magnitude 9.0 earthquake and tsunami that month.
After the cold shutdown, the limit will be lowered to the normal level of 100 millisieverts every five years and 50 millisieverts per year, Komiyama said.
But the allowable limit will remain at 250 millisieverts until April 30 next year for some 50 nuclear experts at Tokyo Electric Power Co., whose expertise is vital in bringing the plant under control.
Kyodo Press, November 15, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/11/15/20111115p2g00m0dm016000c.html
Gov’t decides to ban shipments of rice from part of Fukushima
TOKYO (Kyodo) — The government instructed Fukushima Gov. Yuhei Sato Thursday to ban shipments of rice harvested this year in the Onami area of Fukushima city as rice with excessive levels of radioactive cesium was detected there, Chief Cabinet Secretary Osamu Fujimura said.
This is the first time the central government has banned shipments of rice following the accident at the Fukushima Daiichi Nuclear power plant in the prefecture, severely damaged by a series of explosions soon after the March 11 earthquake and tsunami.
Excessive levels of radioactive cesium were found Wednesday in rice harvested in the Onami area, the first time such levels of the isotope have been detected in the national staple since the nuclear emergency.
The cesium in the rice samples taken at a farm in the city measured 630 becquerels per kilogram, against the provisional 500-becquerel limit set by the central government, according to the local government.
After testing rice samples from all the 48 cities, towns and villages in the prefecture where rice has been grown this year, including the Onami area, the Fukushima governor declared last month that the crop produced in the prefecture was safe.
Kyodo Press, November 17, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/11/17/20111117p2g00m0dm069000c.html
Radioactive Leaks from TEPCO Plant Decreasing
Tokyo, Nov. 17 (Jiji Press)—The amount of radioactive material released from Tokyo Electric Power Co.’s <9501> crippled nuclear power plant has decreased further, a joint task force set up by TEPCO and the government said Thursday.
At present, the amount of radioactive cesium leakage from the damaged reactors at the Fukushima No. 1 nuclear power plant is estimated at 60 million becquerels per hour, down from 100 million becquerels a month ago, the task force said.
Based on these estimates, the annual radiation dose at the plant’s boundary are put at 0.1 millisievert, far lower than the target level of one millisievert, according to the task force.
“We have made steady progress,” nuclear disaster management minister Goshi Hosono said at a news conference. “We believe we can achieve Step Two of the road map within the year.”
The task force released its seventh update to the road map for containment of Japan’s worst nuclear crisis. The plant was badly damaged by the March 11 earthquake and tsunami.
Jiji Press, November 17, 2011
http://jen.jiji.com/jc/eng?g=eco&k=2011111700854
Fukushima begins model decontamination project in no-entry zones
FUKUSHIMA — A model decontamination project to work out specific methods for cleaning up areas tainted by radioactive materials from the Fukushima No. 1 nuclear power plant began here on Nov. 18.
Starting from Okuma, which is host to the damaged nuclear plant, the government began measuring the amount of radiation in one or two areas designated for the model project in a total of 12 municipalities near the plant.
The collected data will be used for decontamination operations in all affected areas in the prefecture, as well as to measure the decontamination effects after the clean-up operations are completed.
The first examined location for the project was a residential area near Okuma town hall. Approximately 30 workers measured radiation levels on the ground surface and at one centimeter and at one meter above the ground in each 10-meter-square section.
Radiation data was also gathered at approximately 100 other locations in the area considered as possible “hot spots,” such as under trees and shrubs.
According to the Japan Atomic Energy Agency (JAEA), the highest radiation level measured within the area on that day was 43.4 microsieverts per hour.
The pre-decontamination monitoring will continue until around Nov. 20, followed by the first decontamination operations of the area planned to start within November, the JAEA said.
Mainichi Shimbun , November 19, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/11/19/20111119p2a00m0na011000c.html
Radiation-tainted sludge, ash continues to pile up at Yokohama treatment centers
YOKOHAMA — Nearly six months have passed since sludge and ash contaminated with radioactive materials from the Fukushima No. 1 nuclear plant stopped being shipped from processing facilities here to cement manufacturers.
Two facilities in the city now hold over 5,500 metric tons of ash, and that figure continues to rise. The city is under pressure to find storage space and explain to residents how the ash will be buried, but no immediate solution to the problem is in sight.
At the beginning of this month, I visited the southern sludge treatment and recycling center in Yokohama’s Kanazawa Ward, where some 4,000 tons of ash — over 70 percent of the city’s total — is stored.
The 16,000 cubic meters or so of sludge that is produced at sewage plants in Yokohama each day is divided up equally and processed at the city’s northern and southern treatment centers. The southern center previously handed incineration ash over to cement manufacturers, but after businesses stopped collecting the ash in mid-May due to the detection of radioactive materials, ash started piling up at the center.
Bags of ash covered with plastic sheets formed mountains on the premises. The amount of ash is increasing at a rate of 20 tons a day at the center. Seeing them up close, I felt the ominous weight of the nuclear crisis, which had seemed a distant affair to me up until then.
Though the center grounds seem spacious, they have their limits. The Yokohama Municipal Government is considering bringing in storage containers to secure more space, but when asked about the time limit for storing the tainted ash, center head Yoshikichi Takahashi appeared grim.
“If the amount overflows here, then sewage treatment facilities will come to a halt, and so will (the city’s) water system lifelines. This is originally drainage water from homes. I want people to consider this an issue close to home,” he said.
In May, the amount of radioactive cesium detected in ash at the southern treatment center exceeded 5,000 becquerels per kilogram, but by the end of October the level was below 2,000 becquerels per kilogram. Cement businesses are expected to consider receiving shipments again if the level falls below 300 becquerels per kilogram, but this will take time.
Mio Sugino, Mainichi Shimbun
* Mainichi Shimbun, November 16, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/11/16/20111116p2a00m0na022000c.html