Outfall tunnel planned for wrecked nuclear facility

Tokyo Electric Power Company Holdings (TEPCO) has drawn-up plans following the Japanese government’s decision in April 2021 to proceed with the project. Around 1.27 million tonnes of treated water will be released into the ocean via a roughly 2.5m-diameter, 1km-long undersea tunnel lying 12m below sea level. The tunnel’s length is hoped to be sufficient to ensure the water discharge does not affect the local fishing industry. China, South Korea, Pacific island states, local residents and fisherman are strongly opposed to the project.

Drilling the tunnel through bedrock would commence near the No 5 reactor which, having survived the catastrophe, poses less likelihood of causing contamination or leakage in and around the tunnel. A spokesperson for the plant said the controlled release of water would continue for around 30 years – or the length of time required to decommission the plant.

Since 2011, radioactive liquid has been stored in multiple tanks at the plant. It is a cocktail of water that was used for cooling, plus that which has subsequently entered the site, whether through precipitation or groundwater ingress. TEPCO says it plans to treat the liquid and dilute it with large amounts of seawater prior to discharge. It anticipates completing the tunnel by spring 2023 when the discharge would begin.

The Fukushima nuclear plant was destroyed by a tsunami caused by an earthquake in March 2011. In July 2021, the United Nation’s nuclear watchdog reached an agreement with the Japanese government to help monitor and review the water discharge.