Photo: The remaining parts of Reactor 3 building. The photo was taken in June 2015. No newer overview has been updated about Reactor 3. [URL]
The temperature of the groundwater in the Fukushima plant area is observed to be rising despite the continuous efforts to freeze the ground as an impervious wall.
On the 28th of October, 2021, Tepco announced a part of the impervious wall consisting of frozen soil is possibly breached due to the rising temperature of the groundwater. The issued part is located in the Southwest of Reactor 4, the depth is reportedly 1 ~ 4 meters underground.
The impervious wall was built and maintained being aimed to reduce the groundwater flowing into the reactor buildings. Regardless of the cost and electricity consumption in order to maintain the shape, the effectiveness has been questioned from the beginning. According to Tepco, the possible breach of the wall, however, did not cause any significant change in the water level.
The rising temperature has been, in fact, monitored since August. Tepco knew the temperature rose from -15 to 10℃ through September but did not publicly report about this.
The cause has not been identified.