Japan nuclear crisis drags on but experts hopeful

TOKYO, (Reuters) – Workers battled to staunch  radiation leaks at a Japanese nuclear plant today, almost  two weeks after it was disabled by an earthquake and tsunami,  but some experts saw signs the crisis was being brought under  control.
Hundreds of workers have been desperately trying to cool  down the six reactors and spent fuel ponds at the Fukushima  Daiichi plant, 240 km (150 miles) north of Tokyo, since the  March 11 disaster, including pumping in seawater or dropping  water from the air.
Two of the reactors are now seen as safe in what is called a  cold shutdown, but the other four sites remain volatile,  emitting steam and smoke periodically and raising radiation  levels in the vicinity.
But that does not mean the situation is out of control, the  experts said.
“The reactors are more stable as time progresses,” said  Peter Hosemann, a nuclear expert at the University of  California, Berkeley.
“By now, the decay heat is greatly reduced and it becomes  easier to supply sufficient water for cooling. As far as we  know, the containments are holding and the radiation levels have  dropped.”
But he added: “We might see some more release of radioactive  material, mostly due to the water going through the systems.”
“The situation is stable but it’s still critical. We have  some small items of positive news,” said Klas Idehaag, reactor  inspector at the Swedish Radiation Safety Authority.
Temperatures in reactor 3, for instance, had fallen to 185  degrees Celsius (365.00F) from 225C a day earlier and  electricity was working more widely at the plant, he said.
Officials at Tokyo Electric Power Co, the plant’s operator,  said the delay in repairs was at least partly due to  underestimates of the damage from the disaster.
Upturned roads, broken pipes and debris hindered transport  of equipment and replacement parts, and one official said  connecting cables to wet equipment in the dark interior of the  reactor buildings had been “far more challenging than expected”.
After more than a week, workers managed to connect power to  the reactors, but since seawater has been used to cool the  plant, checks are needed on all systems before electricity can  be switched back on.
Once coolers are switched on, reactor temperatures should  fall rapidly and the plant could be on its way to being declared  safe, the experts said.
“The problem of testing all the systems has caused some  delays,” said Tony Irwin, a former nuclear plant manager who now  lectures at Australia National University.
“Obviously there must have been quite a lot of building  damage. It doesn’t seem to be too much of a risk because it all  seems to be stable. As soon as you can resume cooling, it should  be OK.”
“It’s much more hopeful than before the weekend…the most  difficult thing is keeping the (spent fuel) ponds cool, where  they are using fire hoses,” said Tony Roulstone, a nuclear  energy expert at Cambridge University.
He said that lower levels of radiation were also allowing  more workers to join shifts on the site, despite health worries.
A Japanese nuclear expert said the main risk was from  continued radiation leaks, and the risk of criticality, or a  self-sustaining nuclear reaction, was low.

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