05. 2011年4月15日 05:30:18: EGaQ73B5yp
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http://gsn.nti.org/gsn/nw_20110414_5466.phpJapan Plant Emits More Radiation After Cooling Lapse Thursday, April 14, 2011 The Fukushima Daiichi nuclear power plant in Japan emitted a new burst of radioactive material this week after a bungled cooling effort apparently affected spent atomic fuel in the site's No. 4 reactor cooling pond, the Associated Press reported (see GSN, April 13). Workers were firing water into the pond from a distance in an effort to prevent the fuel from overheating and releasing radioactive contaminants, but fluid collecting in an adjacent flood control container triggered an incorrect warning that the pond had been filled. Personnel halted water transfers to the pool for a number of days in response to the warning, allowing heat and radiation levels to increase even though the fuel was thought to have remained submerged, Japanese Nuclear and Industrial Safety Agency Deputy Director General Hidehiko Nishiyama said. Water spraying began again on Wednesday. The six-reactor plant was crippled by the 9.0-magnitude earthquake and devastating tsunami that hit Japan on March 11; the projected death toll of the events exceeds 26,000 people, though authorities have found the remains of only 11,250 individuals to date. A series of smaller tremors in recent days might have contributed to incorrect feedback from equipment at the facility, according to authorities. An uptick in radiation at the cooling pond indicates the fuel in storage there had been compromised, authorities said. Concentrations of iodine 131, cesium 134 and cesium 137 have increased in the pond, said Junichi Matsumoto, an executive for plant operator Tokyo Electric Power. Nishiyama, though, suggested "fuel rods in the pool are largely intact, or still keeping the normal shape of what they should look like." "If they were totally messed up, we would have been looking at different sets of numbers from the water sampling," the official said (Yamaguchi/Yuasa, Associated Press/Time, April 14). Separately, plant personnel on Tuesday and Wednesday transferred roughly 660 tons of radiation-tainted water out of a underground passage and into a steam condenser at the site's No. 2 reactor, Kyodo News reported (Kyodo News I, April 14). The condenser can hold as much as 3,000 tons of fluid, the Xinhua News Agency reported (Xinhua News Agency, April 14). Still, the passage's water depth increased by roughly 1.8 inches since Wednesday evening, probably due to ongoing water transfers into the No. 2 reactor, Nishiyama said in the Kyodo report. "There is believed to be around 20,000 tons of water (in the No. 2 reactor turbine building and the trench connected to it), we're feeling the difficulty of lowering the level of the water in a stable manner," the official said. Contaminated water has hindered efforts to restore cooling mechanisms needed to help prevent additional radioactive material from escaping the site. Workers intend to eventually transfer 60,000 tons of fluid flooding underground portions of the facility, including turbine areas at the plant's No. 1, No. 2 and No. 3 reactors. Fluid in the No. 2 reactor's turbine area was thought to contain more radioactive contaminants than water elsewhere at the plant, possibly due to damage sustained by that reactor's fuel rods. Concerns of the fluid spilling into the ocean prompted officials to prioritize its removal. The heat level in the No. 3 reactor's pressure vessel at one point appeared to spike, but the plant operator said the reading was probably the result of a technical error (Kyodo News I). Delays in efforts to drain the radioactive water and restore cooling mechanisms might necessitate a different strategy for stabilizing conditions at the plant, Reuters quoted Nishiyama as saying. "It may be difficult to completely remove the contaminated water and so allow work to proceed. We may need to think of other options," he said (Mayumi Negishi, Reuters I, April 13). Acting on a government order issued on Wednesday in response to the more recent smaller earthquakes, Tokyo Electric Power began studying the ability of reactor structures at the facility to withstand additional tremors, Kyodo News reported. The company must inspect plant components and weigh repairs to any vulnerable areas, the atomic safety agency said. Still, the operator warned it might not "immediately conduct an investigation" due to potential risks around areas slated for inspection (Kyodo News I). Personnel were looking for damage to walls, floors or pipelines at the plant's main waste treatment area and in other sections where radiation-tainted water has collected, the Asahi Shimbun reported. The primary worry, though, was the potential for new tremors to cut off electricity to pumps being used to move coolant into the site. "Any cutoff of the cooling mechanism is an extremely dangerous development," said Matsumoto, the Tokyo Electric Power executive (Asahi Shimbun I, April 14). Personnel are expected to relocate auxiliary electricity sources at higher elevations as a precaution against potential new tsunamis, Kyodo News reported (Kyodo News I). Tokyo Electric Power intends to lift spent fuel out of the No. 1, No. 3 and No. 4 reactors using massive cranes mounted on metal framing to be erected around each site, the Asahi Shimbun reported, referring to company records. Company sources expressed uncertainty, though, that the cranes would be capable of moving 100-ton fuel storage casks without posing a hazard. Another technique under consideration involved transferring spent fuel to a newly built cooling pond before moving it into casks. "It will be impossible to conduct the work now because of the high radiation levels," one company leader warned. In addition, the process could require years to complete, plant operator sources said (Asahi Shimbun II). Toshiba and Hitachi have both drafted proposals for shuttering the facility, the Wall Street Journal reported on Wednesday. Each company produced original equipment used at the plant. Hitachi's plan -- prepared with support from General Electric, Exelon and Bechtel -- could take roughly three decades to fully execute, spokesman Masanano Sato said. Toshiba's proposal -- developed with assistance from the Shaw Group and Babcock & Wilcox -- is based on a 10-year time line. A Tokyo Electric Power representative declined to specify whether the operator would follow one of the plans or request that the firms collaborate. "We are not at a stage yet where we can discuss the proposals," Masataka Shimizu, the company's president, said on Wednesday (Juro Osawa, Wall Street Journal, April 13). Meanwhile, authorities on Thursday began searching the exclusion zone extending six miles from the plant for people missing since last month's earthquake and tsunami, AP reported. Ruins in the area could contain the remains of as many than 1,000 people (Yamaguchi/Yuasa, Associated Press). Trace levels of iodine 131 and cesium 137 is turning up in water supplies in only a small number of prefectures, the International Atomic Energy Agency said on Wednesday. The governments was advising residents of just one Fukushima village to avoid giving tap water to small children (International Atomic Energy Agency release, April 14). Radioactive cesium concentrations 25 times in excess of lawful levels were found in fish pulled on Wednesday from ocean water near Fukushima, Kyodo News quoted the government as saying (Kyodo News II, April 13). Separately, Tokyo dropped a prohibition on transporting "kakina" vegetables from Tochigi prefecture when radioactive contaminants in the food returned to allowable levels, Japanese Chief Cabinet Secretary Yukio Edano said on Thursday (Kyodo News III, April 14). The World Health Organization on Tuesday said there was "very little public health risk" beyond an area extending 18.6 miles from the facility, Reuters reported (Nebehay/Westall, Reuters II, April 12). Japan might have overstated the Fukushima disaster's magnitude to reduce the expense to insurance firms, a top Russian atomic official said on Wednesday. Tokyo on Tuesday upgraded the plant's incident level from 5 to 7, a classification reserved for the most severe nuclear crises. "It is hard for me to assess why the Japanese colleagues have taken this decision. I suspect, this is more of a financial issue, than a nuclear one," said Sergei Kiriyenko, who heads the Russian state-owned nuclear firm Rosatom. "It could be linked to the definition of force-majeure with regard to insurance. I would pay attention to that. It is a bit strange," Kiriyenko said (Alexei Anishchuk, Reuters III, April 13). Russian customs officials in recent weeks halted deliveries of 49 vehicles from Japan found to have unacceptable radioactive contamination, ITAR-Tass reported on Thursday. The vehicles were placed in containers pending a decision on their use (ITAR-Tass, April 14). South Korea on Thursday indicated it would require Japan to officially vouch for the safety of food produced in 13 jurisdictions near the Fukushima facility, the Korea Herald reported (Bae Ji-sook, Korea Herald, April 14). In the United States, drinking water in Chattanooga, Tenn., contained the second-greatest iodine 131 concentration of any water supply in the country, the Chattanooga Times-Free Press reported. “The results being reported are well under the levels of health concerns,” said Tennessee American Water spokeswoman Kim Dalton said. “We will continue to follow the situation closely.” Elevated levels of radioactive contaminants are unlikely to persist if the Fukushima plant is brought under control, said Mike Stafford, head of the nuclear and radiological protection office at the Oak Ridge National Laboratory in Tennessee. “You’ll see patterns that will be linked to the jet stream and where there was a rain right before (the sample was taken),” he added (Pam Sohn, Chattanooga Times-Free Press, April 14). State signatories to the Convention on Nuclear Safety agreed to address the Japanese atomic crisis in a special weeklong conference next year, Kyodo News reported. The governments wrapped up a 10-day meeting on Thursday (Kyodo News IV, April 14). ---------------------------------------------------- |
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