An Invisible River Flowing Underground: Memories of Contamination Carved into the Sand Cushion Drane at the Fukushima Daiichi Nuclear Power Plant (2011)

An Invisible River Flowing Underground: Memories of Contamination Carved into the Sand Cushion Drane at the Fukushima Daiichi Nuclear Power Plant (2011)
Immediately after the accident in March 2011, another accident was quietly taking place at the Fukushima Daiichi Nuclear Power Plant in a place that could not be seen from outside the buildings. That place was the sand cushion drain in the sand layer of the foundation. During normal operation, this layer was merely a gentle water vein to catch groundwater and guide it to a drainage channel. However, when the core damage and containment vessel breakage caused large amounts of contaminated water to overflow into the buildings, the sand layer, which should have been clean, was transformed into an escape route to receive the contaminated water. The aging building foundations sustained minor damage from the shaking of the earthquake, and the bottom of the building was exposed to water pressure and high temperatures, causing the contaminated water to flow into the drain, the lowest point of the building.

This structure was not recognized as a dangerous pathway before the accident. However, as post-accident investigations progressed, it became clear that the underground network of sand layers, ditches, trenches, and intakes was intricately interconnected and that contaminated water could reach the open ocean through the ground. In fact, in April 2011, highly contaminated water was found to have leaked into the ocean in a pit near the intake of the Unit 2 reactor, confirming that the underground pathway played a decisive role in the spread of the accident. Behind the explosions and white smoke above ground, underground rivers, hidden in the shadows of the buildings, were quietly but surely carrying radiation.

In addition, the Fukushima Daiichi Nuclear Power Plant was based on a design concept from the 1970s, and at that time there was insufficient research on groundwater behavior in anticipation of a major accident. There were virtually no models to predict how underground leaks would spread, and it was difficult to know in advance how the hydraulic system on the premises would behave in the event of an accident. The groundwater level became unstable immediately after the earthquake, and the large volume of water flowing in from the ocean and mountain sides mixed with the contaminated water, turning the entire plant site into one giant water vein. Reflections on this initial invisible outflow lay deep in the background of the need for the frozen soil wall that was constructed in later years.

Sand cushion drainage is not a place name. However, it is another geographical feature that runs beneath the ground of Fukushima Daiichi and is an important point that illuminates the accident from the other side. On that day in 2011, people saw white smoke and explosions, but what carried the shadow of the accident was an invisible river running deep underground. But what carried the shadow of the accident was an invisible river flowing deep beneath the ground.