Fukushima workers doused by contaminated water leak

The Fukushima plant has faced a series of problems since the 2011 crisis

Six workers at Japan's Fukushima nuclear plant have been doused in radioactive water, its operator says.

The incident happened after a worker removed a pipe connected to a water treatment system at the plant, Tokyo Electric Power Company (Tepco) said.

A senior official from Japan's nuclear watchdog said he did not believe the workers had received a "seriously troubling" dosage of radiation.

Fukushima has been hit by a series of toxic water leaks in recent months.

The plant was badly damaged by the earthquake and tsunami of March 2011. Cooling systems for reactors were knocked out, causing meltdowns at three of them.

Water is being pumped in to cool the reactors. However, this creates large amounts of contaminated water that must be stored securely.

Some of the water has leaked from the tanks, pipes and damaged structures, leading to concerns contaminated water is mixing with groundwater that is flowing into the sea.

'Carelessness'

The detached pipe was connected to a desalination system, Tepco said, which was being used to treat toxic water before storage in tanks.

Tepco said it was measuring the radiation that the workers, who were wearing protective gear, were exposed to.

"It is serious in that it was another problem caused by carelessness, but I do not believe it is a seriously troubling dosage," Shunichi Tanaka, chairman of Japan's Nuclear Regulation Authority, was quoted as saying by Reuters news agency.

Japanese officials say the water to which the workers were exposed was emitting beta decay radiation - and that is important, says Jonathan Amos, the BBC's science correspondent.

Beta particles are very weakly penetrating, and the workers' protective overalls would have substantially limited their exposure. The reports suggest also that no water splashed in the faces of the clean-up staff, so there would have been little chance of contamination being ingested.

But the incident is just the latest in a series of mishaps at the plant, and it will no doubt bolster the view of those who believe Tepco is bungling the recovery operation, our correspondent adds.

The pipe had since been reconnected and the toxic water was contained, Tepco said.

The incident is the latest involving worker error. On Monday, it was reported that a plant worker accidentally switched off power to pumps used for cooling the damaged reactors.

Last week, workers overfilled a storage tank, and about 430 litres (100 gallons) of radioactive water may have leaked from the tank, with some possibly flowing into the sea, Tepco said.

Water from the storage tanks has seeped into the groundwater and then into the sea. Efforts to use a chemical barrier to prevent sea contamination have not worked.