Fukushima Daiichi NPS Prompt Report 2015

Efforts to contain rainwater continues around tank area, cause of contamination to be investigated

FUKUSHIMA, March 10, 2015 -Tokyo Electric Power Company reported to the Nuclear Regulatory Authority today that approximately 750 tons of rainwater containing Strontium90 may have seeped into the ground around the "H4" tank area. The company explained that the water is unlikely to leak out to the ocean through any of its drainage channels but it is monitoring the situation.

There was heavy rain in Fukushima and rainwater had accumulated around the "H4" tank area, where a simple outer dyke was built to prevent the spread of any leakage from the inner dyke, which is built for the purpose of protecting the tank area. The outer dyke has a protective sealing which is designed to contain water, but it was possible that some water may have seeped out from some seams, the company said. As the company analyzed rainwater within the outer dyke, gross beta levels, which is the total amount of nuclides emitting beta rays such as Strontium90 ranged from 150 to 8,300 Bequerels per liter. Cesium levels were not detected.

It has been confirmed that there is no inflow into the closest drainage channel located to the sea side of "H4" area, nor any significant change in the monitored radioactivity level in the drainage.

After taking initial measures such as pumping out rainwater from the outer dyke, the company said it will continue to take steps to contain rainwater such as further waterproofing the outer dyke.

The "H4" area has experienced tank leakage in the past. TEPCO said it is investigating the cause of the rainwater contamination in this area, and will report its findings promptly.

For measures to prevent leakage from tanks, please see
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2014/images/handouts_140724_04-e.pdf

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 34,000 employees are committed to providing safe, reliable power to its 29.0 million customers, diversifying energy resources to ensure sustainability, and contributing to economic growth while fully meeting its responsibilities after the Fukushima Daiichi accident.
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