Japan: new reactor blast unlikely to cause big leak

A technician in protective gear looks out of a window next to a sign reading ''No entry except for those with permission'' at a makeshift facility to screen, cleanse and isolate people with high radiation levels in Nihonmatsu, northern Japan March 14, 2011, after a massive earthquake and tsunami that are feared to have killed more than 10,000 people.

TOKYO (Reuters) - A fresh explosion at Japan's quake-stricken Fukushima Daiichi nuclear power complex on Monday is unlikely to have led to a large escape of radioactivity, the government said.

Japanese Chief Cabinet Secretary Yukio Edano was speaking after a hydrogen explosion at the No.3 reactor in the plant, which sent a plume of smoke into the air.

Japan's nuclear safety agency later said, quoting a report from the facility's operator, Tokyo Electric Power Co (9501.T), that radiation near the No.3 reactor about 40 minutes after the explosion was about one-50th of that considered critical to human health.

The data suggests the explosion would not have damaged the reactor's containment vessel, a spokesman at the agency said at a news conference.

There were casualties, but the number or other details were not available, the spokesman said.

There is no wind near the plant near the ground and wind above the plant is blowing from the west or from the southwest, the spokesman added, meaning the wind is blowing toward the sea.

The direction of the wind is a key factor in judging possible damage on the environment from the radiation leaking from the plant, which was hit by Japan's biggest earthquake on record and a tsunami.

(Reporting by Elaine Lies and Risa Maeda; Editing by Joseph Radford)