Japan to report nuclear 'melt-throughs' to UN | Inquirer Technology

Japan to report nuclear ‘melt-throughs’ to UN

/ 08:14 PM June 07, 2011

TOKYO – Japan will for the first time report to the UN nuclear watchdog that fuel in its crippled Fukushima plant may have melted through the bottoms of three reactor core vessels, a news report said Tuesday.

The Yomiuri Shimbun daily report came a day after Japan more than doubled its estimate of the radiation released into the air from the plant in about the first week after it was hit by the March 11 seabed quake and tsunami.


Japan’s Nuclear and Industrial Safety Agency (NISA) now says it believes 770,000 terabecquerels escaped into the atmosphere in the first six days — compared to its earlier estimate of 370,000 terabecquerels.

Almost three months after the March 11 disaster, Japan is preparing a report to be submitted this month to the UN International Atomic Energy Agency (IAEA), which sent its own multinational fact-finding team to Japan recently.


Japan’s government plans to tell the IAEA that fuel is assumed to have melted down and through the reactor pressure vessels of units one, two and three and into their outer steel containment vessels, said the Yomiuri.

Tokyo will also pledge to thoroughly reform its nuclear safety systems, including by separating the watchdog NISA from the ministry of economy, trade and industry, which promotes nuclear power, the Yomiuri said.

The news came as a 10-member expert panel independent of the nuclear industry met for the first time to look into the causes of the world’s worst atomic accident since Chernobyl, in Ukraine, a quarter-century ago.

Panel leader Yotaro Hatamura, a Tokyo University professor emeritus on human error, said at the meeting that “nuclear power has higher energy density and is dangerous. It was a mistake to consider it safe.”

NISA’s revised radiation figure released on Monday is likely to fuel criticism of the initially slow and vague flow of information from the government and plant operator Tokyo Electric Power Company (TEPCO).

The new estimate is closer to that of Japan’s independent Nuclear Safety Commission which had initially estimated a release at 630,000 terabecquerels in the first month after the tsunami knocked out reactor cooling systems.

Prime Minister Naoto Kan’s special adviser on the nuclear crisis, Goshi Hosono, said Monday that the latest findings were unlikely to affect the TEPCO roadmap to bring all reactors to stable “cold shutdown” between October and January.


NISA also said in its review that it believes much of the nuclear fuel inside the three reactors melted down faster than previously believed.

The agency said melted fuel in unit one dropped to the bottom of the pressure vessel and damaged it some five hours after the quake hit the plant at 2:46 pm on March 11, followed by a 14-metre (46 foot) tsunami.

The agency said the same happened in unit two at about 10:50 pm on March 14, and that number three suffered damage at 10:10 pm on March 14.

Embattled TEPCO has said it believes the molten fuel is now being cooled by water at the bottom of the number one, two and three reactors, citing the relatively low outside temperatures of the containers.

Months of hosing operations have left over 100,000 tons of highly radioactive water in buildings, basements and ditches at the plant, and TEPCO is struggling to remove the runoff so it can resume crucial repair work.

Contaminated water has spilled or been released several times into the Pacific Ocean, and environmental group Greenpeace has warned that it has found unsafe radiation levels in marine species as far as 50 kilometres offshore.

TEPCO has been testing decontamination equipment, some provided by US and French companies, to remove radioactive substances, oil and sea salt from the runoff water so it can be reused as a reactor coolant from about mid-June.

With the advent of the summer rainy season in the region, they have also started to ship to the plant 370 truck-sized water tanks with a total capacity of more than 40,000 tons to store excess contaminated water.

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TOPICS: Disaster, economy, Environment, Health, Japan, Meltdown, Nuclear Plants, Safety
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