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Friday, May 13, 2011

Melting of reactor 1 fuel 'no surprise'


Staff writer

Experts were not surprised Thursday to find that most, if not all, of the fuel rods in reactor No. 1 at the Fukushima No. 1 power plant had been fully exposed, melted and fell to the bottom of the pressure vessel.

Tokyo Electric Power Co. announced the finding Thursday after workers entered the reactor building earlier this month and fixed equipment to monitor the water level in the pressure vessel.

"It's neither a surprise nor bad news," Kunihiko Takeda of Chubu University told The Japan Times. "This means Tepco has been pumping lots of water in the reactor without knowing what exactly is happening in it, which is the best thing Tepco could do." He added that reactors No. 2 and 3 may also be in the same situation.

The new finding doesn't increase the likelihood of a hydrogen explosion because the temperature in the pressure vessel is still low, experts said.

Hydrogen explosions can occur if zirconium, material used in fuel-rod casings, melts at around 1,200 degrees, said Ken Nakajima of the Kyoto University Research Reactor Institute.

The temperature in the pressure vessel is 100 to 120 degrees.

Tepco has injected nitrogen gas into the containment vessel to dilute the hydrogen density, further decreasing the chance of a hydrogen explosion, he said.

Takeda said the pressure vessels and containment vessels in reactors 1, 2 and 3 are likely to have cracks where hydrogen can escape, another factor reducing the likelihood of a hydrogen explosion. The fact remains, however, that the reactors at the Fukushima plant keep leaking radioactive substances into the air and are irradiating the water cooling them as well. Thus, the most important thing, as it has always been, is to build a system to recirculate the water being used to cool the reactors, Takeda said.

Women abroad chip in

Kyodo

OSAKA — Groups of Japanese women living in New York and London are working on charity projects for victims of the March 11 earthquake and tsunami.

Hope Japan, set up by three women in New York, has raised $8,500 (about ¥690,000) by selling original pins over the Internet for $3 each, while a group of expectant mothers in London has sent more than 2,500 muslin squares — material used as burp cloths, diaper liners or makeshift bibs for babies — to disaster areas.



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The Japan Times

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