Melting « nuclear-news

Fukushima Daiichi Frozen Wall Section Fails

November 26, 2021

A section of the frozen wall at Fukushima Daiichi has melted. The portion south of unit 4 has had problems remaining fully frozen for years. Now TEPCO admits it has melted in recent weeks. This portion of the frozen wall has had issues for years. Recent changes to the nearby K drainage tunnel and a recently discovered crack may be redirecting water from an underground stream into the area of the frozen wall.

TEPCO found sections near the surface of the wall had fully melted. Puddled water was found nearby. The section is relatively small and didn’t impact the lower depths of the wall’s integrity.

TEPCO’s solution is to install steel piling sections between the K drainage canal and this section of the wall, hoping to deflect underground water. This steel wall will not be completely solid. Due to the nature of driving pilings into the ground, there could be gaps as wide as 10 cm.

Once the pilings are installed, TEPCO plans to monitor the area to make sure the problem has been resolved.

https://www3.nhk.or.jp/nhkworld/en/news/20211126_16/

Click to access d211125_07-j.pdf

December 5, 2021 Posted by dunrenard | Fukushima 2021 | Fukushima Daiichi, Ice wall, Melting | Leave a comment

Typhoons cause ‘ice wall’ to melt at Fukushima nuclear plant

Workers examine pipes for the wall of frozen soil at the embattled Fukushima No. 1 nuclear power plant.

Rainfall from recent typhoons caused partial melting of the “ice wall” at the Fukushima No. 1 nuclear plant, allowing highly radioactive water to leak from around the damaged reactor buildings, the plant’s operator said Sept. 1.

Tokyo Electric Power Co. said melting occurred at two sections of the ice wall, which is designed to divert groundwater away from the reactor buildings.

TEPCO officials believe that during the latest typhoon, contaminated water from around the reactor buildings flowed through openings of the ice wall created by the deluge and reached downstream toward the sea.

The groundwater level near a seaside impermeable wall temporarily rose to 28 centimeters below the ground surface when Typhoon No. 10 passed the area on Aug. 30.

Before the typhoon hit, the water level was 35 cm below the surface.

Around 5.5 cm of rainfall a day fell in the area when the typhoon hit.

The groundwater level, however, actually rose by 7 cm, although 740 tons of groundwater was pumped out of the section.

“If there had been an additional 15 cm of rain, (the contaminated water) could have poured out over the ground surface” and spilled into the sea, a TEPCO official said Sept. 1.

The Meteorological Agency’s initial forecast said Typhoon No. 10 would bring a maximum 20 cm of rain a day at some locations in the Tohoku region.

The 34.5-billion-yen ($335 million) frozen wall was completed in spring to prevent groundwater from entering the reactor buildings and mixing with highly radioactive water.

TEPCO admitted the underground wall of frozen dirt is not working.

The company said the temperatures at the two sections of the frozen wall have climbed above zero since Typhoon No. 7 approached Fukushima Prefecture on Aug. 17.

The company believes that the partial melting was caused by the influx of water brought by the typhoons and heavy rain in between.

TEPCO plans to freeze the wall again by pouring chemicals into pipes that extend underground.

http://www.asahi.com/ajw/articles/AJ201609020020.html

September 2, 2016 Posted by dunrenard | Fukushima 2016 | Fukushima Daiichi, Ice wall, Melting, Typhoon | 1 Comment