Radiation fears after third explosion heard at Japanese nuclear plant

As the death toll in Japan continues to mount following Friday’s earthquake and tsunami, Japanese authorities are now dealing with a possible meltdown at a damaged nuclear power plant in the heart of the disaster zone.

A fourth reactor at the plant caught fire late on Tuesday afternoon and radiation levels are now high enough to be a health concern, officials said.

Prime Minister Naoto Kan said those living near the Fukushima Dai-ichi plant should stay indoors to avoid radiation sickness.

The trouble began when the quake and tsunami knocked out the plant’s power, which subsequently disabled the cooling systems which prevent a meltdown. The blast at the nuclear plant may have damaged a container.

Two explosions hit the Fukushima Dai-ichi nuclear plant in northeastern Japan on Monday and early Tuesday, prompting the evacuation of thousands of people from nearby areas.  Monday’s happened at the facility’s Unit 3 reactor, injuring 11 workers. Early Tuesday, Japan’s nuclear safety agency said a second explosion was heard at the plant’s Unit 2 reactor.

Nearly 200,000 people have been evacuated over the past few days due to problems at the plant.

Tokyo Electric warned after the explosion Monday that operators had lost the ability to cool Unit 2, adding that the fuel rods at that reactor were exposed.

There are six reactors at the Fukushima plant, about 60 kilometres south of Sendai, in the heart of the quake and tsunami zone.

Hydrogen in steam released to reduce pressure inside the reactors set off the explosions.

Chief Cabinet Secretary Yukio Edano said there has been “no massive radioactive leakage.” Officials insist radiation levels measured outside the damaged plant remain within legal limits.

There have now been three explosions at the plant in the last four days.

The explosions in Unit 2  and 3 were preceded by a similar blast Saturday in Unit 1. Operators have been frantically trying to cool the reactors using seawater in a bid to prevent a complete meltdown. 

Japanese officials said fuel rods in all three reactors appeared to be melting.

Some experts would classify that as a partial meltdown. Others only use that term to describe a situation when nuclear fuel melts through a reactor’s innermost chamber but not through the containment shell, according to the Associated Press.

A complete meltdown is defined as a situation where the uranium core melts through the outer containment shell. If that were to happen in Japan, the resulting wave of radiation would likely result in widespread health problems.

Up to 160 people may have been exposed to radiation and up to 1,500 people have been scanned.

Japanese Prime Minister Naoto Kan said the quake, tsunami and subsequent economic and nuclear crises are the harshest challenge his country has faced since the Second World War.

The death toll from Friday’s natural disaster could exceed 10,000.

Experts say a Chernobyl situation is unlikely because the Dai-ichi plant has a containment vessel that would capture radioactive materials in the event of a meltdown. Chernobyl had no outer containment shell.

The United States moved an aircraft carrier away from the Dai-ichi plant Monday as a precaution after 17 personnel involved in a helicopter relief mission were exposed to low-level radiation. After being scrubbed down, they were declared contamination-free.

Four nuclear plants in northeastern Japan reported damage from the earthquake and the tsunami.

With files from The Associated Press.

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