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Fukushima Daiichi NPS Prompt Report 2014


Independent monitoring results indicate efforts to protect water are succeeding

FUKUSHIMA, September 12, 2014-Seawater monitoring results outside the port of Fukushima Daiichi Nuclear Power Station show that the multiple measures to address water issues at Fukushima Daiichi Nuclear Power Station are keeping radiation levels in seawater well below regulatory limits, according to Tokyo Electric Power Company (TEPCO).

Since the March 2011 accident at the plant caused by the tsunami following the Great Japan Earthquake, TEPCO and the Japanese Government have worked to reduce the amount of contaminated water flowing from the plant into the sea. Monitoring outside the port of Fukushima Daiichi is not only conducted by TEPCO, but also by a third party, such as the Nuclear Regulation Authority and the Fukushima Prefecture.

Results of the monitoring indicate that radiation levels in seawater outside the port are well below limits set by Japan's government and below even the more stringent limits for drinkable water set by the World Health Organization. The WHO standard allows no more than 10 Bequerels per liter (Bq/L) for any one of Cesium 134, Cesium 137, and Strontium 90. The actual measurements, taken from multiple locations, can be found at wesbites of Japan's Nuclear Regulation Authority, TEPCO, and Fukushima Prefecture (Japanese only).

The data provided at those websites show that even inside the port area, concentrations of radioactivity have been steadily decreasing. Cesium now been measured in amounts below JNRA limits in all points, Strontium also has been measured within regulatory limits at most points within the port, except nearest the reactors, where recent measurements show levels of 70-100 BqL compared with the JNRA limit of 30 Bq/L.

Multiple Strategies to Manage Water

Since the time of the accident, TEPCO has put in place a variety of strategies to reduce the flow of contaminated water into the sea ? strategies that include several projects still under construction. As a result, the estimated outflow of several substances has been cut dramatically. For example, compared with the period before August 2013:

・Strontium 90 has been reduced to approximately a third of earlier levels .
・Cesium 137 has been reduced to a tenth of the volume .

Further improvements are expected as the various water management strategies are completed, including a wall between the facility and the sea designed to block groundwater flow, and a "subdrain system", around the reactor facilities that will capture 500 to 700 tons per day of underground water after operating. These approaches are projected to further reduce Cesium 137 and Strontium 90 outflows to one-fortieth of the current estimated amount of outflow.

Material explaining water strategies including the "subdrain system" and the "seaside impermeable wall" may be obtained at
*Please refer to page 7 of the above material for comparison of the estimated amount of contaminants flowing out through groundwater at Fukushima Daiichi.
Seawater monitoring results around Fukushima Daiichi NPS are posted at


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.

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