Fukushima Daiichi Nuclear Plant Weekly Review

Tokyo Electric Power Co. formalized its plans to decommission the two functional reactors at the Fukushima Daiichi nuclear plant, while a new report shed additional light on efforts to cool damaged units early in the crisis.

Recent news related to the TEPCO plant severely damaged following Japan's 2011 earthquake and tsunami include:

Fukushima unit 1 and 2 vent stack. Source: TEPCOUnits 5 and 6 to Close

Following a board meeting Wednesday, TEPCO applied with Japanese regulators to decommission units 5 and 6. Neither was running during the tsunami. While they lost offsite power along with the rest of the plant, a diesel generator at unit 6 remained functional and allowed the units to avoid the extensive damage that occurred in the other reactors. TEPCO said in a release that it plans to use the decommissioned reactors for full-scale mockup testing of robots, cleanup equipment and devices that will eventually remove the damaged fuel from units 1-3.

Piping Made Fire Truck Water Injection Ineffective

In a desperate bid to feed seawater into overheating reactors early in the crisis,  plant workers connected fire trucks to pipes leading into units 1-3. In a report Dec. 13 following up on unanswered items from an earlier investigation, TEPCO asserted the trucks did, in fact, pump enough water into them to avoid core melting. But much of the water wound up in irrelevant pipes leading to condensate storage tanks and other systems, the Asahi Shimbun reported. TEPCO became aware of the water diversion issue in March of 2011 but had not previously made it public. The utility has since installed electric valves at its Kashiwazaki-Kariwa plant to allow for external water pumping in an extreme emergency.

Photo: Workers use a telescopic camera, dosimeters and other equipment to inspect the exhaust stack of units 1 and 2 on Nov. 22. Measurements at various points revealed doses between 19 millisieverts per hour and 95 millisieverts per hour. The inspections will be used to plan the stack's reinforcement and eventual disassembly.

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