Fukushima Daiichi NPS Prompt Report 2015

Water will be pumped up, treated, tested, and discharged, with the strictest water quality standards maintained throughout steady operations of water treatment facilities

TOKYO, Sep. 2-The subdrain and groundwater drain systems at Fukushima Daiichi Nuclear Power Station, which will intercept groundwater from flowing into the reactor buildings or the port area and as a result further protect the ocean, will be activated after many years of preparation. TEPCO expects that the first pumping up of groundwater by the subdrain system will take place on tomorrow, September 3.

Appreciating the understanding of all concerned parties including Fukushima prefecture and prefectural and national fishermen's associations, TEPCO takes them and their tough decisions seriously and will comply with the operational policies and objectives and carry out the subdrain and groundwater drain plans.

The subdrain and groundwater drain enable water to be collected and pumped up as it flows downhill from around the reactor buildings toward the port area. In a manner similar to the existing groundwater bypass (which intercepts water on the landside of the reactor buildings), the water will be temporarily stored to check its quality and then discharged into the port area, with thorough treatment processes.

The water through the subdrain and groundwater drain is expected to be slightly more contaminated than water from the groundwater bypass at the time it is pumped out of the ground. However, the water will be treated to meet the more stringent quality standards for subdrain and groundwater drain than for groundwater bypass. It will also be monitored more frequently so that the water quality of subdrain and groundwater drain is verified for discharging.

-The upper limit of radioactive concentration for Subdrain and Groundwater Drain:
  Cs-134 1Bq/L, Cs-137 1Bq/L, Gross 3Bq/L, Tritium 1,500Bq/L
-(Reference 1) The upper limit of radioactive concentration for Groundwater Bypass:
  Cs-134 1Bq/L, Cs-137 1Bq/L, Gross 5Bq/L, Tritium 1,500Bq/L
-(Reference 2) WHO Guideline for Drinking-Water Quality:
  Cs-134 10Bq/L, Cs-137 10Bq/L, Gross 10Bq/L, Tritium 10,000Bq/L

After the subdrain and groundwater drain systems are found to be operating stably, the opening that was left in the seaside impermeable wall will be closed to prevent groundwater flowing into the port area. Once it is completely closed, the subdrain and groundwater drain will work to keep groundwater from accumulating behind the impermeable wall.

In addition, the subdrain is expected to reduce the inflow of groundwater to the buildings to half. The volume of water entering the reactor basements, where it becomes contaminated by mixing with the existing contaminated water, is expected to drop to 150 cubic meters a day, from the current 300 cubic meters daily.

In the long term, the pumping systems and seaside wall are expected to be joined with the landside impermeable wall (frozen soil wall) currently under construction, creating a wall around the reactor buildings and further reducing the intrusion of groundwater into those buildings.

For more information about the operation of the subdrain and groundwater drain: http://www.tepco.co.jp/en/decommision/planaction/sub-drain/index-e.html

For more information on the seaside impermeable wall: http://www.tepco.co.jp/en/decommision/planaction/seasidewall/index-e.html
For more information on the landside impermeable wall (frozen soil wall): http://www.tepco.co.jp/en/decommision/planaction/landwardwall/index-e.html

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.
TEPCO Website: http://www.tepco.co.jp/en/index-e.html
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