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QUAKE AFTERMATH: Black smoke (above) rising from a blaze - set off by a massive quake - at the nuclear plant in Kashiwazaki on Monday. The intensity of the tremors also caused then ground near the plant to crack. -- PHOTO: AFP
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TOKYO - MONDAY'S massive earthquake in Niigata prefecture has exposed a hidden danger: A huge nuclear power plant there is sitting astride a geological fault line.
Now the plant may be put out of action for more than a year for safety checks to be undertaken after the quake caused a series of problems, including radiation leaks.
There are also concerns whether the shutdown would lead to power shortages, especially during the current summer period.
The nuclear facility, which has seven reactors and is considered the world's largest in terms of combined output, is located in Kashiwazaki city, the area worst hit by the 6.8-magnitude quake.
It supplies electricity to the greater Tokyo area.
The focus of Monday's quake was 9km from the coast of Niigata, north of Tokyo, and 17km below the seabed.
The safety study to be undertaken by Tokyo Electric Power Company (Tepco), which runs the plant, is aimed at determining whether it is able to withstand a strong tremor.
Tepco has concluded from data relating to aftershocks following the quake that the plant may be sitting on an extension of the fault line.
However, as the fault is believed to lie some 20km below the plant, the company believes that it poses no immediate danger.
Tepco will conduct a geological survey over an area 30km in radius around the plant to ascertain the presence of fault lines, including those under the seabed.
A study that it conducted from October last year to April this year, for the purpose of complying with new quake-resistance guidelines set out by the government last year, had neglected to check for undersea faults.
This week's tremor has raised strong concerns in Japan over just how quake-resistant the country's nuclear power plants - which meet a third of Japan's electricity needs - are.
At one of the reactors at the Kashiwazaki plant, a sensor - which measures how hard the ground shakes during a quake - had shown that the quake's intensity was twice what the plant had been designed to withstand.
Though no physical damage was reported to any of the reactors, severe shaking caused water from a tank containing spent nuclear fuel to be spilt at one reactor and leaked into the sea.
Anger has mounted against Tepco for initially under-reporting the amount of water that was leaked and the level of radiation it contained.
The company said it was due to a computational error and has stressed that the amount of radiation posed no health or environmental hazards.
The quake had also set off a blaze - the first time fire has ever broken out at a nuclear facility in Japan - at an electric transformer next to a reactor which was put out only after two hours.
A report released yesterday by the Niigata prefectural government said several power lines apparently short-circuited when they came into contact with a metallic pipe, and the resulting sparks ignited insulation oil that leaked from the transformer.
Unable to put out the blaze on its own, the plant sought help from the local fire station.
The transformer and the pipe had been damaged when the ground below it subsided because of the tremors.
In fact, the International Atomic Energy Agency (IAEA) had pointed out in 2005 that the firefighting setup at the Kashiwazaki plant was inadequate.
In the wake of Monday's quake, IAEA director-general Mohamed ElBaradei has reportedly advised Japan to do a complete review of its nuclear plants.
Noted the Mainichi Shimbun daily: 'The safety of nuclear plants is not just a domestic problem. The foreign media are also watching very closely.'
wengkin@sph.com.sg
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