Tepco mulls sinking walls around Japan reactors: TV

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The operator of Japan's Fukushima nuclear plant is considering installing underground walls around its crippled reactors to prevent radioactive water seeping out, a broadcaster said on Saturday.

Tokyo Electric Power Company (TEPCO) is studying the measure to contain contaminated water leaking from the plant's reactors which were damaged in the March 11 earthquake and tsunami, TV Asahi said citing unnamed sources.

Workers would have to dig to a depth of 15 metres (50 feet) to reach an impervious layer to build the walls on, it said.

Tepco has dumped a massive amount of water into reactor containers and overheating pools containing spent nuclear fuel rods, after the magnitude 9.0 quake triggered monster waves which knocked out the plant's cooling systems.

Workers battling to stabilise the battered nuclear facility later found highly contaminated water submerging turbine buildings and underground tunnels, with some running off from a cracked concrete pit into the Pacific Ocean.

They sealed the crack but have faced a challenge in trying to ensure no underground water seeps out of the plant.

The report came a day after former construction minister Sumio Mabuchi, who is now one of Prime Minister Naoto Kan's advisors, suggested the plan.

A Tepco spokesman stopped short of confirming the project would go ahead.

"The company considers many possible measures to to do, and it may be one of them," said a company spokesman.

Workers dousing the reactors and fuel rod pools have tried to control the amount of water they use, to limit the quantity of contaminated water produced by the cooling process.

But the temperature at reactor four's fuel pool had risen to 91 degrees Celsius (196 degrees Fahrenheit), forcing workers to add more water to prevent the rods from being exposed and releasing radiation, Tepco said on Saturday.

"The company is considering sending a waterproof CCD camera into the pool, but the temperature is now at 91 degrees C, which is too high," the spokesman said. "But we also need to carefully watch how much water to inject."

The camera would be used to check on the condition of the fuel rods and see if any had melted.