Tepco Restarts Water Clean-up Operation

The Financial Times - By Jonathan Soble in Tokyo - June 23, 2011

About 110,000 tonnes of highly contaminated water have accumulated in basements and service tunnels under the plant’s four crippled reactors, a result of three months’ worth of emergency cooling efforts since the March 11 tsunami. The onset of Japan’s early-summer rainy season has made the situation more critical by adding to the build-up.

The company is already struggling to keep to its timetable for bringing the plant to a safe “cold shutdown” by January – a process that depends crucially on its ability to cycle decontaminated coolant water through the reactors.

Tepco said on Thursday that an instrument failure may have been at least partly to blame for the problems with the water purification system, which has been specially built by Areva, the French nuclear group, and Kurion, a US nuclear-waste disposal company.

Tepco switched the system off on Saturday, just hosurs after it was first turned it on, when radiation levels in the treated water failed to decline as expected. The complex network of filters and chemical separators is supposed to reduce concentrations of radioactive particles to 1/1,000, but contamination levels increased to 1/100.

The apparatus has also been beset by leaks and mechanical breakdowns, adding to public frustration about the pace of repair work at the plant. A headline in the weekly tabloid Shukan Gendai on Thursday demanded to know: “Who chose this useless Anglo-US-Japanese water treatment system?”

Tepco said it had discovered that a by-pass valve that should have been closed while the system was in operation had been left open, with the result that some tainted water was not passing through the filters as designed. An instrument that monitors the status of the valve wrongly showed it to be closed, Tepco said.

It was unclear whether closing the valve would be enough by itself to bring radiation down to the target level.

Emergency crews have been pumping thousands of tonnes of water a day into the reactors since the plant was crippled by the tsunami. The water was initially drawn from the sea, and later from fresh-water-hauling barges. Salt, oil and other contaminants must be separated out as part of the purification process, further complicating the work.

Tepco is aiming to create a closed system that would take tainted water from the reactors, cycle it through the purification system and then pump it back into the reactors – eliminating the need for external water sources and leaving no new water to accumulate under the plant.

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