By Aaron Sheldrick
TOKYO, Oct 15 (Reuters) - A once-in-a-decade typhoon threatened Japan on Tuesday, disrupting travel and shipping and forcing precautions to be taken at the wrecked Fukushima nuclear power plant.
Typhoon Wipha is moving across the Pacific straight towards the capital, Tokyo, and is expected to make landfall during the morning rush hour on Wednesday, bringing hurricane-force winds to the metropolitan area of 30 million people.
The centre of the storm was 860 km (535 miles) southwest of Tokyo at 0800 GMT, the Japan Meteorological Agency said on its website. It was moving north-northeast at 35 kph (22 mph).
The storm had weakened as it headed north over the sea but was still packing sustained winds of about 140 kph (87 mph) with gusts as high as 194 kph (120 mph), the agency said.
The agency issued warnings for Tokyo of heavy rain, flooding and gales, and advised people to be prepared to leave their homes quickly and to avoid unnecessary travel.
A spokesman for the meteorological agency said the storm was a "once in a decade event".
The typhoon is expected to sweep through northern Japan after making landfall and to pass near the crippled Fukushima nuclear power plant, on the coast 220 km (130 miles) northeast of Tokyo, later on Wednesday.
The operator of the plant, Tokyo Electric Power Corp , which has been struggling to contain radioactive leaks, said it would cancel all offshore work and it would decide whether to continue work onshore after assessing the weather.
The utility will also take down cranes and secure all cables, hoses and machinery, a company spokesman said.
Tokyo Electric said it would pump out the rainwater expected to fall into protective containers at the base of some 1,000 tanks storing radioactive water.
The radioactive water is a by-product of its jerry-rigged cooling system designed to keep under control reactors wrecked in a 2011 earthquake and tsunami.
The rainwater that builds up will be pumped into an empty tank, checked for radioactivity, and if uncontaminated, released into the sea, the company said.
Typhoon Wipha is the strongest storm to approach eastern Japan since October 2004. That cyclone triggered floods and landslides that killed almost 100 people, forced thousands from their homes and caused billions of dollars in damage.
Four Japanese oil refining companies said they suspended marine berth shipments in eastern Japan as the typhoon approached but there was no impact on refining operations.
The affected facilities are Idemitsu Kosan Co's Chiba and Aichi refineries, JX Holdings Inc's Negishi, Kashima and Sendai refineries, Fuji Oil Co's Sodegaura refinery and Cosmo Oil Co's Chiba refinery.
Japan Airlines Co cancelled 183 domestic flights on Tuesday and Wednesday, mostly from Tokyo's Haneda airport. Rival ANA Holdings Inc halted 210 flights in Japan with three international flights also cancelled. The combined cancellations will affect 60,850 passengers, the airlines said.
East Japan Railway Co said it had cancelled 31 bullet trains going north and west from Tokyo.
Nissan Motor Co said it was cancelling the Wednesday morning shift at its Oppama and Yokohama plants south of Tokyo. Oppama makes the all-electric Leaf and other models.