TEPCO ROBOTIC EXPLORATION OF UNIT 3 AT FUKUSHIMA DAIICHI
Starting July 19, TEPCO began a multi-day robotic exploration of the Unit 3 reactor at Fukushima Daiichi, with the aim of determining conditions inside the Primary Containment Vessel including pedestal area.
The inspection is part of a long-term effort at all three of the Fukushima Daiichi reactors that experienced meltdowns during the March 2011 accident, to gain a complete picture of conditions in preparation for the eventual removal of fuel debris.
Prior photographic inspection of the Unit 3 reactor suggests that, during the accident, fuel assemblies melted from the excess heat, dropping from their original position down to the pedestal area. In this process, it is believed the pedestal area may have experienced some damage, and the robot will attempt to acquire images and data to provide a better understanding of those conditions.
The schedule for the effort, which is subject to modification depending on what is found, calls for photographs to be taken on the first day and reviewed on the second. Then, depending on what is found, the robot will be used again to focus on areas of particular interest.
The robot has been inserted into the PCV through a pipe that is designed to protect against the escape of any radioactive gas from the reactor. No radiation impact has been occurred to the surrounding environment and no significant changes have been observed at the monitoring posts and dust monitors after the investigation on July 19, compared to the before. Once inside the PCV, the robot is designed to navigate underwater – a necessity as cooling water has accumulated in the PCV since the time of the accident. The robot is equipped with thrusters to move it in different directions through the water, and with front and rear cameras. It was developed by IRID, the International Research Institute for Nuclear Decommissioning. (Source: Tepco)