Japan nuclear crisis drags on but experts hopeful

TOKYO: The workers have fought to stop the leakage of radiation in a Japanese nuclear plant on Thursday, nearly two weeks after being disabled by an earthquake and tsunami, but some experts have seen signs of the ongoing crisis in control.
Hundreds of workers desperately tried to cool the six reactors and spent fuel pools at the plant in Fukushima Daiichi, 240 km (150 miles) north of Tokyo, from March 11 disaster, including the pumping seawater or dropping water from the air.
Two reactors are now considered safe in what is called a cold shutdown, but the other four remain volatile, emitting steam and smoke regularly and to raise levels of radiation in the vicinity.
But this does not mean that the situation is out of control, experts said.
"The reactors are more stable over time," said Peter Hosemann, a nuclear expert at the University of California, Berkeley.
"At that time, the decay heat is reduced and it becomes easier to provide sufficient water for cooling. As we know, and hold the containment radiation levels have fallen."
But he added: "We could see a bit more of the radioactive release, mainly because of water through the system."
Officials from Tokyo Electric Power Co., operator of the plant, said the delay in the repair was at least partly due to under-estimate the damage caused by the disaster.
roads inverted broken pipes and debris hindered the transport of equipment and replacement parts, and one official said connecting cables to equipment in wet dark interior of buildings from the reactor had been "much more difficult than expected. "
After more than a week, workers were able to connect the power reactors, but since the sea water was used to cool the plant, controls are needed on all systems before electricity can be delivered walking.
Once the devices are powered up, the reactor temperature should drop rapidly and the plant could be on track to be declared safe, according to experts.
"The problem of testing all systems has led to some delays," said Tony Irwin, Manager of the former nuclear plant who now teaches at the Australian National University.
"Obviously, it must have been a lot of damage to buildings.
It does not seem too great a risk, because everything seems to be stable. As soon as you can resume cooling, it should be OK. "
A Japanese nuclear expert said the main risk of radioactive leaks had continued, and the risk of criticality, or a reaction self-sustaining nuclear, was low.
"The possibility is not zero, because nobody can look inside the reactors to see what happens," said Yoshiaki Oka, professor at Waseda University in Tokyo.
"The nuclear fuel rods could cause heart of the fusion reactor, the core could heat and melt the equipment around him. But as we make sure the heat is out of circulation pumps and nuclear fuel is covered by water, the risk is remote. "
Hosemann, University of California, Berkeley, said the crisis should go out early next month.
"There is still a little early to forecast the exact time, but I think in a few weeks, the reactors will be cool enough to say that the crisis is over," he said.
"There will always be important to provide sufficient cooling to the reactor and spent fuel pools for a longer period of time.
But as this is guaranteed and we do not see a significant additional amount of radioactivity released, I am convinced that the situation is under control "-. (Reuters)