Six workers at Japan's crippled Fukushima nuclear plant were exposed to a leak of highly radioactive water on Wednesday, the latest in a string of mishaps the country's nuclear watchdog has attributed to carelessness, saying they could have been avoided.

 

Tokyo Electric Power Co, also known as Tepco, has been battling to contain radioactive water at the plant, which suffered triple meltdowns and hydrogen explosions following a devastating earthquake in March 2011.

 

In the latest incident, a worker mistakenly detached a pipe connected to a treatment system to remove salt from the hundreds of tonnes of water Tepco pumps over the melted fuel in wrecked reactors at Fukushima to keep them cool.

 

The accidents at the Fukushima Daiichi plant, 220 km (130 miles) north of Tokyo, are adding to a crisis no one seems to know how to contain, and stirring doubt over Tepco's abilities to carry out a complex cleanup widely expected to take decades.