Fukushima Daiichi NPS Prompt Report 2015

After years of preparation and discussion, combination of seawall, subdrain, and groundwater drain activation will secure water management for the site

FUKUSHIMA, August 11 - After years of preparation and discussion, a system designed to block the contaminated water into the ocean at Fukushima Daiichi is being prepared to be put to use, the latest milestone in an accelerating rate of progress in the fight against contaminated water at the site.

The system combines three key elements: an "sea-side impermeable" wall facing the sea, and a subdrain and a groundwater drain system that captures the blocked water so that it can be pumped up and sent to the on-site water treatment facility. These elements have been approved by the government, but TEPCO has been trying to obtain the understanding of this system to other interested parties, such as the fishermen, before the wall can be fully closed.

The Government permission was required because the plan requires the treated water to be returned to the ocean, as is currently the case with the water diverted through the "groundwater bypass" system. Like the subdrain and the groundwater drain system, the bypass uses pumps to draw water from the ground, which is then treated, held for testing, and released. The main difference is that the "bypass" water is intercepted on the mountain side of the plant, and the subdrain system captures water surrounding the reactor buildings and the groundwater drain at the port area.

Although the subdrain and the groundwater drain water is expected to be slightly more contaminated than the bypass water at the time it is pumped out of the ground, it will be held to the same stringent post-treatment standards, and subject to the same monitoring program, as the bypass water.
Water will be temporarily stored and tested before release, to ensure that no water is released until it has already met stringent standards. These safeguards will protect the environment while avoiding the need for long-term storage.

Activation of the seawall/subdrain/groundwater drain system is projected to reduce the flow of water from the mountain side into the plants by approximately 150 tons.

Once the company gains understanding from interested parties to activate the system, the subdrain and groundwater drain pump will be officially activated, and the seawall fully closed later. Currently, activation date has not been determined, and prefectural fishery association submitted its own request to the government and TEPCO today. To fully close the wall, nine rods must be driven into the ground and the last segment of the wall dropped into place and made watertight.

Latest Step Forward in Water Management

If the seawall/subdrain/groundwater drain combination have been activated, these elements will further secure the water management at Fukushima Daiichi, something that has challenged engineers since the March 2011 accident. Because the facility sits at the base of the mountains next to the sea, rainwater and groundwater constantly flow downhill through the site.
Some of it becomes contaminated by mixing with water already on the site, or other contaminated structures.

Seawall/subdrain/groundwater drain materials could be found from following pages;
http://www.tepco.co.jp/en/decommision/planaction/seasidewall/index-e.html
http://www.tepco.co.jp/en/decommision/planaction/sub-drain/index-e.html

Preventing this water from entering the ocean, and reducing the amount of contaminated water on the site - for the sake of the surrounding communities - has been and remains a priority. Successfully managing it has required the development and deployment of multiple innovative strategies, and the participation of many international companies and contractors alongside TEPCO workers. Recent milestones include:

*Completion and removal of 99% of the heavily contaminated water in the underground tunnels known as "trenches."
*Completion of the groundwater bypass system, which reduced the flow of groundwater into the reactor buildings by 25 percent.
*Construction and testing of the "land-side impermeable (frozen soilwall)" which eventually will form part of a complete perimeter around the four reactor buildings.
*Improvements in the treatment and storage of water, including treatment of almost all the contaminated water that was being stored on site, and the replacement of leak-prone flanged tanks (which, of necessity, were hastily constructed after the accident) with sturdier welded tanks.
*Other measures, such as stronger protections against tsunamis,sealing of the surface to limit groundwater contamination, and improvements to various drainage channels on the site.

[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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