NRA to allow part of frozen soil wall at Fukushima plant — The Asahi Shimbun

” The nation’s nuclear watchdog decided that Tokyo Electric Power Co. can start freezing soil in a limited area around crippled reactor buildings at the Fukushima No. 1 nuclear power plant to prevent radioactive water accumulating in the buildings from leaking into the ground.

The conditional permission by the Nuclear Regulation Authority on Feb. 15 means TEPCO will get the go-ahead for a section of frozen soil wall in the area of the complex facing the sea.

Initial plans called for TEPCO to surround the four reactor buildings with a 1,500-meter-long circular frozen soil wall by inserting 1,568 pipes to a depth of 30 meters at 1-meter intervals. Each pipe would then freeze the soil around it once liquid of minus 30 degrees circulated inside the cylinder.

Building the wall was intended to prevent the flow of groundwater into the reactor buildings, where melted nuclear fuel has accumulated in the basements, thereby reducing the volume of water contaminated with radioactive substances.

TEPCO completed the installation of the pipes on Feb. 9.

However, the NRA was worried that the level of groundwater inside the frozen soil wall could drop drastically once the frozen soil wall surrounds the reactor buildings, causing levels of highly contaminated water in the reactor buildings to become higher than the groundwater level. That, NRA officials feared, would cause the highly contaminated water to leak into the ground.

With caution the buzzword of the day, the NRA had called on TEPCO to change plans and operate only a part of the frozen soil wall.

In a meeting held Feb. 15, the utility said it would freeze only the soil on the side of the stricken facility facing the sea.

Once the NRA grants official approval, TEPCO will move quickly to freeze the soil.

TEPCO also said that it wants to freeze the remaining portions in a step-by-step manner. The NRA supported the proposal, saying it would make it possible to “collect data on water levels.”

However, the two sides did not reach any agreement on this other than to continue their discussions. ”

source

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