Thousands evacuated as authorities seek to shut down reactors

Sat, Mar 12, 2011, 00:00

NUCLEAR ISSUE:THOUSANDS OF people were evacuated from their homes last night as Japan scrambled to shut down reactors and prevent a catastrophic meltdown at a nuclear plant that bore the brunt of the earthquake and subsequent tsunami, amid reports that its cooling system had failed.

Efforts were underway to prevent nuclear fuel rods from overheating at the Fukushima plant in Japan’s northeast, which was starkly exposed to the full force of the tsunami.

The government declared a nuclear emergency, and the trade minister admitted that a radiation leak was a possibility as concerns mounted that the cooling system had failed, with grave implications for the integrity of the hundreds of tonnes of radioactive fuel at the site.

Some 2,800 local residents were forced to flee their homes, evoking scenes witnessed after the Chernobyl accident in Ukraine almost 25 years ago.

There was dispute last night as to whether the US air force flew in coolant, as stated by US secretary of state Hillary Clinton.

Japanese authorities said pressure was rising inside the plant with the risk of a radiation leak, according to the Jiji news agency. One British atomic engineer said the evacuation suggested a radioactive leak remained a possibility.

“It looks very serious. Obviously we do not know exactly what is going on, but evacuating people is normally only a matter of last resort when there is only one containment layer left to be breached,” said John Large, a member of the British Nuclear Engineering Society and a fellow of the Royal Society.

Another nuclear expert said if the water-cooling system had broken down, the consequences could be dire.

“One critical safety issue is the maintenance of water cooling systems to ensure that the nuclear fuel inside the reactor core does not heat up to unsafe levels,” said Shaun Burnie, a consultant on the nuclear industry.

He said the reactor’s operator, Tokyo Electric, had apparently been unable to pump cooling water into the 40-year-old reactors for at least three hours.

“The possibility is that the reactor fuel is already damaged. If they are unable to restore coolant pump capacity, then the fuel will continue to heat up, eventually the fuel will be exposed to air at which point a whole series of events can unfold, including steam explosions, fuel meltdown and loss of containment.”

Others cautioned that it was too soon to declare that a nuclear disaster was imminent. Sue Ion, fellow of the Royal Academy of Engineering, said the evacuations could equally be a sensible precaution and noted that Japanese reactors were built to withstand the rigours of nature in an earthquake-prone part of the world.

“As this is an earthquake zone, the Japanese apply very rigorous standards, with robust designs and regulations,” she said.

Paul Haigh, a fellow of the Institution of Chemical Engineers, added: “All Japanese reactors are designed to withstand substantial earthquakes. Instrumentation is provided for the early detection of tremors which would lead to a controlled shutdown of the reactor. These systems appear to have successfully shut down the affected reactors.

“Modern western reactors, including those planned for the UK, are already designed to withstand significant seismic events.” Rather than undermining public faith in nuclear energy, this incident would highlight its safety, Ms Ion predicted. “People should gain confidence from the fact that these plants have shut down as they should be.”

Dozens of new nuclear plants are planned in Britain, the US and China amid public concern about energy shortages and low carbon ways of tackling climate change.

However, the nuclear industry was preparing for a wave of bad publicity surrounding the 25th anniversary of Chernobyl, where work is still under way to dismantle the plant and make safe spilled radioactive fuel.

This plant – built and operated under the Soviet system – blew up during a safety test, although the accident was blamed on a mixture of bad design and human error.

Failure of the cooling system and the diesel back-up generator at the Fukushima plant raises questions about what has gone wrong so far and what could happen in the future.

Mr Large said a complete power outage would quickly lead to the reactor overheating and the potential meltdown of the fuel. Different mechanical and chemical reactions could lead to a hydrogen explosion, he added.

All of this could be “astronomically” expensive, given the heavily populated and insured population of Japan, said Mr Large.

He expressed concern that the nuclear industry and local political system had a reputation for considerable secrecy that would not make it easy to discern what had gone wrong.

In 1999, 2004, 2005, 2007 and 2009, reactors shut down because of seismic activity.

Confidence in Japan’s nuclear safety was dented by a series of scandals in the late 1990s when the Tokyo Electric Power Company, owner of the Kashiwazaki-Kariwa plant, admitted falsifying safety data and concealing cracks in the core structures of its reactors. The same plant was seriously damaged by a major earthquake in 2007, but the owners tried to conceal a radiation leak. Much of the plant had to be closed for 21 months at a cost of more than $3 billion. – ( Guardian service)