Japan nuclear crisis far from over

By Richard Alleyne, Science Correspondent

The restoration of power to the stricken plant, 140 miles north of Tokyo, had led to hopes that the threat of a meltdown and major radiation leak was past.

But scientists say they are not out of the woods yet and they still face some of the most difficult and dangerous tasks.

They include manually draining hundreds of gallons of radioactive water from the plant and "bleeding" radioactive gas from the pumps and piping of the emergency cooling systems.

Technicians are also increasingly concerned about salt build-up inside the reactors caused by evaporated seawater.

Crusts forming around fuel rods could block cooling water from getting to the radioactive fuel and cause them to start heating up again.

Hundreds of thousands of pounds of salt crystals are thought to have been deposited around the plant and if it is too thick will need to be manually chipped away.

Work making the plant safe also requires a technician to reach a dozen valves, sometimes using a ladder – with a great risk of radiation exposure.

The treacherous nature of the tasks was underlined yesterday when three workers were taken to hospital with radiation burns, caused by wading through water as they laid cables.

Public alarm about the crisis increased earlier after officials announced that levels of radioactive iodine had been detected in Tokyo’s tap water.

Despite levels having subsided yesterday the fear is that more radiation is being released than has been first understood.

There were no fresh incidents of smoke or steam at the plant but four of the plant's reactors are still considered volatile, although on the way to stability.

"It's still a bit early to make an exact time prognosis, but my guess is in a couple of weeks the reactors will be cool enough to say the crisis is over," said Peter Hosemann, a nuclear expert at the University of California.

"It will still be important to supply sufficient cooling to the reactors and the spent fuel pools for a longer period of time. But as long as this is ensured and we don't see any additional large amount of radioactivity released, I am confident the situation is under control."

Tokyo's 13 million residents were told not to give tap water to babies under one year old after contamination hit twice the safety level this week. But it dropped back to allowable amounts.

Radiation above safety levels has also been found in milk and vegetables from Fukushima and press reports said radioactive caesium 1.8 times higher than the standard level was found in a leafy vegetable grown in a Tokyo research facility.

Singapore said it had found radioactive contaminants in four samples of vegetables from Japan.

Earlier, it and Australia joined the United States and Hong Kong in restricting food and milk imports from the zone, while Canada became the latest of many nations to tighten screening after the world's worst nuclear crisis since Chernobyl.

A shipping industry official, meanwhile, said some merchant vessels may be avoiding Tokyo port due to concern that crew members may be exposed to radiation.

Radiation particles have been found as far away as Iceland, and although Japan insists levels are not dangerous to adults, it is the nation's most testing time since world War Two. Telegraph