Fukushima Daiichi NPS Prompt Report 2014

FUKUSHIMA, July 23, 2014-New approaches to removing the contaminated water from trenches surrounding Fukushima Daiichi's Unit 2 and 3 reactor facilities are being actively explored, the Tokyo Electric Power Company said today.

These strategies were discussed in a meeting today between TEPCO officials and Japan's Nuclear Regulation Authority, and at least some of them are planned to be implemented by next month.

Goal is to Remove Water

The trenches contain highly contaminated water that has flowed out from the basements of the two buildings, where it collects as the result of cooling water and groundwater that leaks into the basement from various loopholes within the structure such as space around the pipes after coming into contact either with nuclear material or other contaminated water within the buildings.

In April, TEPCO attempted to freeze the water outside Unit 2 before removing it from the trenches. By attempting to freeze the water, engineers hoped they could remove it without causing additional contaminated water to flow out of the buildings and into the trenches.

But because the water is flowing in and out of the trenches, due to the pumping up of water from the buildings, it has proved exceptionally difficult to freeze despite the success of early experiments. As a result, the company is now looking at several alternatives:

· Upgrade the cooling capacity of the freezing system
· Suppressing the flow of the water
· Exploring other methods of lowering the water's temperature

The company has already increased the flow of coolant, and may additionally add ice or dry ice to the trench water to lower its temperature. If none of these approaches work, the company may install additional pipes to carry coolant, and insulate the pipes in the trenches with additional nylon bags filled with cement. Still other strategies may include filling spaces with grout or other materials.

Efforts to freeze the trench water outside Unit 3 haven't begun yet. Once the water is successfully frozen, removal from each unit is expected to take three to four months.

Difference between the "Ice Wall" Construction and the freezing at trenches

Unlike the trenches, where the challenge is to freeze flowing water into ice, the "ice wall" really doesn't involve ice at all. Rather, it uses a proven technology to freeze the surrounding soil, which in turn is expected to prevent groundwater from reaching the basements of the reactor buildings. The technology has been used successfully in many construction sites. The difficulties encountered in freezing the flowing trench water have had no impact on the way to construct the "ice wall," which is proceeding toward completion in 2015.

Water Management Efforts

The continuing efforts to clear the contaminated water from the trenches is part of TEPCO's multi-pronged efforts to improve water management at Fukushima Daiichi, clean contaminated water already on the site, and reduce the quantity of water that becomes contaminated in the future.

"We are committed to these efforts," said Site Superintendent Akira Ono, "and will continue to pursue these alternatives until we have successfully removed the water from the trenches."

Detailed material on the additional measures may be obtained at
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2014/images/handouts_140723_03-e.pdf

Basic idea and original method of removing water from the trenches are explained in the video at
http://photo.tepco.co.jp/en/date/2014/201402-e/140218-01e.html
*Method of freezing is explained at around 5:50 in the video. Part of the video may be out of date.

About TEPCO

Tokyo Electric Power Company, Inc. (TEPCO) is Japan's largest power company, supplying energy to the greater Kanto area, including Japan's two most populous cities, Tokyo and Yokohama. Its 35,000 employees are committed to providing safe, reliable power to its 28.8 million customers, diversifying energy resources to ensure sustainability, and contributing to economic growth while fully meeting its responsibilities after the Fukushima Daiichi accident.
TEPCO website: http://www.tepco.co.jp/en/index-e.html
TEPCO Facebook page: http://www.tepco.co.jp/en/facebook/index-e.html