Fukushima Daiichi Nuclear Plant Weekly Review

Tokyo Electric Power Co. is drilling wells to divert groundwater around its severely damaged Fukushima Daiichi nuclear plant. Meanwhile, the company also predicted a slight increase in radiation levels at the plant boundary and the demolition of a cover surrounding unit 1.

Fukushima unit 1 reactor building. Source: TEPCODevelopments this week related to the nuclear plant blacked out following Japan's 2011 earthquake and tsunami include:

New Groundwater Strategy

An estimated 400 metric tons of groundwater flows into Fukushima reactor buildings daily and comes in contact with radioactive contaminants. After controlling the damaged reactors, storing that radioactive water soon became the biggest challenge at the plant, with 280,000 tons in surface tanks, another 100,000 tons in reactor basements, and little room to store more. On Tuesday, TEPCO announced it dug 12 wells west of the reactor buildings to pump out groundwater before it reaches the units. If TEPCO receives approval, the Asahi Shimbun reported, the company plans to discharge that water into the sea.

Dose at Plant Fence to Increase

Also on Tuesday, TEPCO said it may exceed a self-imposed 1 millisievert per year dose limit at the plant's boundary, Kyodo reported. The dose may rise to 7.8 millisieverts per year because of water transfers from leaking underground storage tanks.

Cover Coming Off Unit 1

TEPCO plans to temporarily remove a cover placed around unit 1 in October of 2011 to help contain radioactive contaminants. According to a TEPCO release and a Kyodo report, its removal this fall will facilitate debris removal from around the spent fuel pool and eventual fuel removal.  With reactor and SFP temperatures under control, and with nitrogen injection and dust suppression measures in place, the cover removal is not expected to increase dose levels significantly outside the unit. TEPCO estimated the operation will increase the dose at the site perimeter by 0.0004 millisieverts per year.

Photo: An image of an upper level of unit 1 taken with a camera suspended from a balloon in October. Source: TEPCO

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