Tokyo Electric Power Co. this week outlined additional measures to freeze contaminated water in tunnels at Fukushima Daiichi and also released an estimate of airborne contamination released during cleanup efforts last year.Recent developments related to the nuclear plant severely damaged following Japan's 2011 earthquake and tsunami include:New Strategy Proposed to Freeze TunnelsCrews have tried unsuccessfully since April to freeze tunnels connecting the turbine buildings of units 2 and 3 to block the highly contaminated water that constantly flows through them. On Wednesday, TEPCO told Japanese regulators it is exploring several alternatives to its current approach. These include increasing the volume of coolant used, reducing the amount of water reaching the tunnels and adding ice or dry ice to them. The company is also considering the installation of additional cooling equipment, insulating pipes within the tunnels or filling parts of them with grout or other materials. Once a plug of ice is established, TEPCO said in a release that removal of water from the surrounding area is expected to take three to four months. That must be accomplished before a larger plan to freeze soil around the damaged reactors can be completed.2013 Debris Removal Increased Airborne ContaminationAlso on Wednesday, TEPCO told the Nuclear Regulation Authority that radioactive material estimated at up to 1.1 trillion becquerels reached the environment during a four-hour period of debris removal last summer. Radiation alarms sounded at the time. While the exact amount released is unknown, the Asahi Shimbun reported, TEPCO said the estimate is based on a particularly high-dose 20-minute period and might be an over-estimate. In response to the event at unit 3 last August, TEPCO has sprayed anti-dust agents after debris removal, whereas it was previously only used beforehand.
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