10 Septembre 2012
Sleeping dragon: Reactor 4 at the Fukushima No. 1 power plant is seen July 18, the day Tepco removed an unused nuclear fuel assembly from the spent-fuel pool to check the extent of damage its fuel rods sustained in the March 2011 disasters. KYODO
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.
The facility is wholly owned by Sandia Corp., a subsidiary of Lockheed Martin Corp., and undertakes research for the Department of Energy's National Nuclear Security Administration.
"Last week, I showed slides of the Sandia lab experiments to some Diet members. Afterward, Tokyo Electric Power Co. officials presented their plan to empty the nuclear fuel from the reactor pool," Gundersen said.
"I told Tepco that while I realized they hoped and believed that there will always be water in the nuclear fuel pool, I had to ask whether or not they had (already prepared and stationed) any chemicals to put out a nuclear fuel pool fire in the event they were wrong.
"Tepco's response was that there was nothing in the fuel pool that could burn, a statement I find appalling."
In July, Tepco announced it had removed two unused nuclear fuel assemblies from reactor 4's pool, the first of more than 1,500 that will have to be retrieved. If everything goes according to plan, the utility will begin extracting the remaining assemblies, used to store spent fuel rods, from December 2013 and complete the task within three years.
But the state of the fuel pool and the lack of preparations to deal with a possible fire has drawn intense criticism not just from experts like Gundersen but also from some senior officials in the U.S.
Sen. Ron Wyden, a member of the Senate Committee on Energy and Natural Resources who visited Fukushima Prefecture in April, sent a letter to Japan's ambassador in Washington upon his return urging Tokyo to tap the expertise and knowhow of the United States and other countries to complete the cleanup work more quickly.
"Tepco's Dec. 21 remediation road map proposes to take up to 10 years to complete spent-fuel removal from all of the pools on the (Fukushima No. 1) site," Wyden wrote.
"Given the compromised nature of these structures due to the events of March 11, this schedule carries extraordinary and continuing risk if further severe seismic events were to occur.
"Many nations possess expertise in nuclear energy technology and its full breadth should be made available to Japan in dealing with" the Fukushima disaster, the letter said.
Later that month, 72 domestic antinuclear groups, along with former Ambassador to Switzerland Mitsuhei Murata and ex-U.N. diplomat Akio Matsumura, called on the United Nations to establish a nuclear security summit to specifically focus on the spent-fuel pool at reactor 4 and to also establish an independent assessment team to investigate the matter.
However, Gundersen said he is still awaiting signs from the Japanese government or Tepco officials indicating they're ready to canvass a broad range of experts around the world over how best to deal with not only the unit 4 situation, but the larger question of what to do with the Fukushima No. 1 plant.
"Japan's Nuclear and Industrial Safety Agency and Tepco claim they are getting outside expertise from the International Atomic Energy Agency, but Article II of the IAEA's charter states its mission is to promote nuclear power. There is a real need for experts who think outside the box," Gundersen said.