On the 29th, Tokyo Electric Power Company (TEPCO) released new images taken using an underwater robot during an internal investigation of the Unit 1 reactor containment vessel at the Fukushima Daiichi Nuclear Power Plant (Okuma Town and Futaba Town, Fukushima Prefecture). Inside the reinforced concrete base (1.2 meters thick) supporting the pressure vessel where the nuclear fuel had been stored, the concrete had disappeared and the internal reinforcing bars were exposed. This is the first time that damage to the inside of the foundation has been confirmed.
The published image was taken on the 28th. The inside of the foundation was photographed from the opening (approximately 80 centimeters wide and 1.7 meters high) that connects the bottom of the containment vessel to the bottom of the pressure vessel.
The side wall near the opening was damaged at the bottom and the rebar was exposed. The heat from melted nuclear fuel (debris) may have melted the concrete, and if the damage is severe, the pressure vessel could collapse. Previous investigations had confirmed that the outside of the foundation was damaged.
On the 29th, the robot entered directly under the pressure vessel through the opening for the first time to investigate the damage inside the foundation in detail. The images will be released on the 30th. (Kenta Onozawa)