福島原発事故はまだ収拾していない。それどころか今だ大きな危険を孕んでいる。見守っている世界の原子力エキスパートたちと日本政府・東京電力の対処対策との隔たりと、その苛立ちがわかる記事。
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Global help urged to avert reactor 4 pool fire
U.S. expert appalled by Tepco's attitude over 'sleeping dragon' risk
By ERIC JOHNSTON Japan Times Staff writer
Saturday, Sep. 8, 2012
KYOTO — The risk of a fire starting in reactor 4's spent-fuel pool at the Fukushima No. 1 plant continues to alarm scientists and government officials around the world, prompting a leading U.S. nuclear expert to urge Japan to tap global expertise to avert a catastrophe.
Go global: U.S. nuclear expert and opponent Arnie Gundersen addresses an audience Monday in Kyoto, after traveling to Japan to meet with Diet members and citizens' groups over conditions at the Fukushima No. 1 power plant. MICAH GAMPEL
Arnie Gundersen, a nuclear engineer and former executive in the nuclear power industry who is now one of its foremost critics in the United States, has been monitoring the No. 1 plant since the March 2011 triple meltdowns through his Vermont-based Fairewinds Energy Education nonprofit organization.
During a trip to Japan in late August and early September, Gundersen met with Diet members, lawyers and citizens' groups to discuss conditions at the wrecked power station and told an audience in Kyoto on Monday that fears over the spent-fuel pool in reactor 4 remain high.
"The spent-nuclear-fuel pool at Fukushima No. 1's unit 4 remains a sleeping dragon. The situation and possibility of a fuel pool fire in reactor 4 in the days (immediately) after the (March 2011) quake was the reason the U.S. government recommended that the evacuation zone be (set at) 80 km," said Gundersen, who served as an expert witness during the federal investigation into the 1979 Three Mile Island disaster in Pennsylvania.
This evacuation recommendation was based on studies the U.S. conducted more than a decade earlier at New York's Brookhaven National Laboratory, which is owned by the U.S. Department of Energy and researches atomic energy.
"In 1997, the laboratory did a study showing that if a nuclear-fuel pool were to boil dry, it would release enough radiation to cause the permanent evacuation of those living within an 80 km radius (of the complex).
"The Fukushima plant's reactor 4 (pool) has 1,500 fuel bundles. That's more cesium than was released into the atmosphere from all of the nuclear bombs ever exploded, (which total) more than 700 over a period of 30 years. That's also why the U.S. recommended an evacuation with an 80 km radius," Gundersen explained.
But even today, concerns persist among experts worldwide that reactor 4's pool is still at risk of boiling dry. If this were to occur, it would necessitate a massive and immediate evacuation of the surrounding area.
Nuclear fuel rods are extremely thin and clad with zircaloy, a zirconium alloy that contains a tiny amount of tin and other metals. But zircaloy burns if it is exposed to air, as shown in a test conducted at the Sandia National Laboratory in New Mexico just two weeks before the Great East Japan Earthquake devastated the Tohoku region.
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