Fukushima Daiichi NPS Prompt Report 2014

Identification of leakage points is a step toward removal of nuclear fuel

FUKUSHIMA, June 5, 2014- A high-tech robot camera built by Hitachi-GE Nuclear Energy has for the first time obtained clear pictures of places in the damaged Unit 1 reactor at Fukushima Daiichi where coolant water is leaking from the containment vessel into the building's basement, TEPCO announced.

Identifying and eventually plugging the leaks is a critical step not only in the management of contaminated water at the site, but, even more importantly, toward the eventual removal of the fuel itself.

The general location of the leakage was first identified last November by a remote-controlled boat that took photographs while floating on the accumulated water in the basement, outside the containment vessel. At that time, it became clear that it would be necessary to examine more deeply around the suppression chamber, which is the outer part of the containment vessel, to identify the source of the leaks with more precision. Because radiation is high around the vessel, it could only be safely examined by remote control.

To meet this need, TEPCO worked with Hitachi-GE Nuclear Energy to develop a robotic camera that could be safely lowered into the suppression chamber and controlled from a separate building hundreds of meters away where workers can safely operate with little or no protective gear. Over a three-day period from May 27-30, the camera was successfully lowered the 2.7 meters down to where the chamber locates and videos were taken of the leaks, using the device's ability to pan, tilt, and zoom.

The photographs revealed leakage around an elastic joint ("flexible joint") on the piping coming from the containment vessel. The joint is believed to be suffering from corrosion. A total of .75 to 1.5 tons of water per hour is estimated to be leaking from the area investigated, and TEPCO will continue efforts to identify and ultimately plug all the leaks. This must be accomplished before the reactor's fuel can be safely removed.

For videos, photos, and additional information, please go to
http://photo.tepco.co.jp/en/date/2014/201405-e/140527-01e.html (May 27)
http://photo.tepco.co.jp/en/date/2014/201405-e/140530-01e.html (May 30)

Information for the investigation conducted in November 2013 may be seen at
http://www.tepco.co.jp/en/press/corp-com/release/2013/1232195_5130.html

About TEPCO
Tokyo Electric Power Co., 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.