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Thursday, 19 February 2015

Walking atop an underground battle


February 19, 2015
FUKUSHIMA -- The mass of machinery that engineers hope can stem the relentless flow of water into the gutted Fukushima Daiichi nuclear power plant impresses by its sheer size as well as its ambitious aim.
     Huge 55cm-diameter ducts snake out from the roof of the refrigeration plant that forms the heart of this beast, which Tokyo Electric Power Co. showed the media for the first time Wednesday. When it starts beating, a minus 30 C solution of calcium chloride will course through them at 2 meters per second.
     This refrigerant will circulate through more than 1,500 buried pipes encircling four of the plant's six reactor buildings. If all goes according to plan, a "frozen earth" wall will form, stopping the influx of groundwater that now leaks back out as streams of radioactive contamination.
     The refrigeration plant houses 30 units, each with a capacity of about 70 tons of refrigeration, defined as the heat reduction needed to freeze a ton of 0 C water in 24 hours. To put this in perspective, a Tepco guide described it as the freezing capacity of two tuna-fishing ships.
     While the system entails 3.5km of ductwork, it will operate by the same principle as a household fridge. After absorbing heat from the soil and re-emerging from the ground, the refrigerant, now warmed up to minus 20-something, will be cooled back down to the right temperature with CFCs. All 30 units will go on full blast until the soil congeals, after which about half will be turned off, Tepco said.
     Only about 15% of the equipment is in place. Tepco plans to start freezing the ground on the inland side, which is about 90% finished, before closing the circle on the coastal side.
     Tepco had initially aimed to complete the installation by the end of March. But a fatal accident brought everything to halt for roughly two weeks while the company performed safety checks. Work resumed Feb. 3 but is running two to four weeks behind schedule.
     "We're putting safety before our schedule," Fukushima Daiichi manager Akira Ono said.
     Roughly half of the workers at the plant call Fukushima Prefecture home. For them, staying safe is not only about protecting themselves, but also about sparing their disaster-ravaged communities any more pain.
     Snow fell at the plant on the day of the media tour. Gloves were little help against the biting cold, and the goggles shielding our eyes from radiation kept fogging up. For the 6,000-plus workers a day who toil at the ruined plant, such grim conditions have become a fact of life.
Source: Nikkei Asian Review
http://asia.nikkei.com/Japan-Update/Walking-atop-an-underground-battle
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