Repair Work Resumes at Crippled Japanese Nuclear Plant

Despite occasional sightings of smoke and steam billowing from damaged reactor buildings at the Fukushima-1 nuclear power plant in Japan, the effort has resumed to restore electricity and critical cooling functions. Radiation continues to be detected above normal

levels as far as 300 kilometers south of the facility, which was knocked out of commission by a huge quake and tsunami nearly two weeks ago.

After a break, because of concerns about smoke and radioactive steam, workers at the Fukushima-1 nuclear power plant on Thursday resumed the attempts to repair the cooling system at the Number 3 reactor.

That is the considered to be the most dangerous unit, because its fuel contains a mix of uranium and plutonium.

Video taken from a helicopter Thursday morning shows what appears to be steam rising from four of the nuclear facility's six reactor buildings. However, authorities say the situation is not serious enough to continue a halt in the critical work to prevent a potentially larger catastrophe.

A re-emergence of black smoke at the Number 3 reactor halted work Wednesday.

There is also fresh concern about the damaged Number 1 reactor where pressure inside the reactor again increased.

Japan's chief cabinet secretary Yukio Edano says crews are trying to maintain a delicate balance between spraying water on the radioactive fuel, which causes a rise in pressure, and reducing the water flow which could see temperatures increase to a dangerously high level.

Edano says experts are watching the situation closely and there is no evidence that the reactor vessel has been damaged by excessive pressure.

Since the March 11 magnitude 9.0 earthquake, which triggered a destructive tsunami, the nuclear power complex has experienced many serious problems. These include hydrogen explosions in reactor buildings, radiation leaks, exposed and overheating fuel rods, damaged reactor cores and shaking from powerful aftershocks.

Tokyo Electric Power Company, the plant operator, has also revealed that it spotted 13 times, between March 13 and 16th, a radioactive "neutron beam" about 1.5 kilometers from the Number 1 and 2 reactors.

Some scientists say this means uranium and plutonium might have leaked from the plant's nuclear reactors and the exposed used nuclear fuel rods have discharged a small amount of neutron beams via fission.

James Symons, the director of the nuclear science division at the Lawrence Berkeley National Laboratory in California, expresses surprise and skepticism about the report.

"A neutron beam would be a beam of neutrons, which are a neutral particle. They are certainly produced in a fission reaction inside a reactor. But if neutrons escape and were to come out of the reactor they would not be visible. So you would not see a neutron beam," he said. "Plus Ican't imagine a process in which neutrons would be emitted from the reactor in a beam."

The physicist says, at this stage, the Fukushima disaster has more in common with 1979 Three Mile Island partial meltdown, in the United States, than the 1986 Chernobyl catastrophe in Ukraine.

"All these things are different. But it's closer," said Symons. "It's certainly very unlike what happened at Chernobyl where the entire reactor exploded basically. It's certainly very serious, but - as far as we can tell - it's also coming under control."

Radiation continues to be detected in the surrounding air, soil and sea water.

Japan's government is now advising people beyond the 30-kilometer exclusion zone around the Fukushima plant to remain indoors. Officials say that, since the explosions, some infants theoretically may have accumulated 100 millisieverts of radiation in their thyroids.

Some scientists say those exposed to that total radiation dose should take potassium iodide, because an annual dose of 100 millisieverts is believed to be associated with an increased risk of cancer.

Japan's science ministry says radiation levels detected in Tokyo have tripled, compared to those detected earlier in the week.

The Tokyo metropolitan government, as well of those of the adjacent prefectures of Chiba and Saitama, have announced levels of radioactive iodine considered unsafe for infants were detected this week in tap water.

That has prompted panic buying of bottled water.

Vegetable shipments have been stopped out of areas adjacent to the crippled nuclear power plant after some leafy greens were found to be contaminated with radioactive iodine and cesium exceeding government standards.