TOKYO, March 13 - The wind over Japan's earthquake-damaged nuclear complex will shift from the south to a westerly on Sunday night, blowing any radioactivity toward the ocean, a weather official said.
The Fukushima Daiichi plant, run by Tokyo Electric Power Co (TEPCO), is about 240 km (150 miles) north of Tokyo on the country's northeast coast, facing the Pacific Ocean.
The wind will blow from the west until around midnight Sunday in the area, the Japan Meteorological Agency official said. On Monday the wind will blow from the south-west, then later from north-west, he said.
The wind speed will be around 2 to 3 meters per second, he said. Typically the direction of the wind with that speed tends to change easily in a day, he added.
The direction of the wind is a key factor in judging possible damage to the environment from radiation leaking from the plant, which was devastated on Friday by Japan's biggest earthquake on record and a subsequent tsunami.
Officials are working desperately to prevent fuel rods from overheating in a first reactor after some radiation leaked into the air. The government said on Sunday that a building housing a second reactor was at risk of exploding.
South Korea, to the west of Japan, saw little chance of any radiation blowing across its territory.
"We see no impact (from Japan's radiation) so far as the current winds are westerlies," said Lee Durk-hun, head of operational safety analysis at the Korea Institute of Nuclear Safety.
"However, if the winds change, it could affect us, and according to our close monitoring systems, we will prepare measures to prevent any damage."
China, the Koreas and Russia's far east are the regions closest to Japan, but all lie on the west of the main disaster zone.
Authorities in China's northeastern province of Liaoning have begun monitoring for possible radiation from Japan, but have not yet detected any, Xinhua news agency reported.
"At present the figures are normal and Liaoning has not been affected," it quoted nuclear safety official Gao Kui as saying.
(Reporting by Junko Fujita, Ben Blanchard in Beijing and Meeyoung Cho in Seoul; Editing by Jonathan Thatcher and Mathew Veedon)