Recent leaks from a novel type of radioactive water treatment device, currently under trial runs at the crippled Fukushima No. 1 nuclear power plant, occurred from corrosion holes in welds, Tokyo Electric Power Co., the plant operator, said July 25.
The finding was presented to a session of a joint government-TEPCO council that is tasked with promoting measures for decommissioning the stricken reactors at the Fukushima plant.
While the trial runs of the "Alps" multi-nuclide removal equipment were scheduled to end in mid-August, solving the leak problem is expected to push back that date by four months, further exacerbating the uphill fight against radioactive water that keeps accumulating at an alarming pace at the hobbled plant.
The Alps device is considered a key weapon for fighting the increasing volume of radioactive water. It can eliminate 62 sorts of radioactive substances, including strontium, from contaminated water. Although the device cannot eliminate tritium, a radioactive isotope of hydrogen, it is expected to help reduce the overall risk levels in the event of a radioactive water leak.
The Alps equipment has three channels, called A, B and C, made of the same composition. Each channel is supposed to treat up to 250 tons of radioactive water a day.
The leaks occurred in stainless-steel tanks for holding untreated radioactive water in channel A. The first discovery came on June 15, when a TEPCO worker found brown-hued traces of water that had dripped from one of the tanks during a trial run.
TEPCO halted the operation of the channel to conduct investigations, which led to the discovery of very small holes. The chloride ion and hypochlorous acid contents in radioactive water had corroded welds in the tanks that are 9 millimeters thick, TEPCO officials said.
According to the officials, TEPCO plans to cover the interiors of the tanks with rubber lining to deal with the problem. TEPCO also plans to halt channel B, currently under a trial run, in early August to repair the tanks and take similar measures in channel C, which has yet to enter a trial run.
The suspension of trial runs in all channels will leave TEPCO without the means to treat radioactive water over a period of one-and-a-half months.
The Alps equipment was initially scheduled to have entered trial runs in September 2012. But it took workers more time than expected to deal with weaknesses found in its radioactive waste containers. The device only entered trial runs at the end of March.
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