A robot on Friday crept into the deadly primary containment vessel of reactor 1 of the Fukushima No. 1 power plant to surveil its damaged interior, Tokyo Electric Power Co. said.
It is the first time a robot has entered the PCV of any of the three stricken reactors at the meltdown-hit plant, and the snake-like contraption might give the utility a better idea of what happened to the pressure vessel and its core in the disaster.
Tepco plans to have the robot check half of the first floor of the bulbous PCV on Friday and examine the other half on Monday.
Ultimately, the utility plans to explore the underground portion of the vessel, where the melted fuel rods are believed to have puddled. But that is not yet feasible because the robot isn’t waterproof. A waterproof version is expected to be developed by the end of next March.
The snake-like robot, about 9.5 cm high and 60 cm long, entered the vessel through a pipe 10 cm in diameter. After going down to the first floor, it was to assume a U shape and measure temperature and radiation levels. It was also to photograph the interior and check for obstacles in the area leading to the underground portion.
When a measuring device was snaked into the same vessel in October 2012, the radiation peaked at a deadly 11 sieverts per hour.
The fuel in reactor Nos. 1 to 3 is believed to have melted through their reactor pressure vessels and spread to the primary or other containment vessels. But the exact details are still a mystery more than four years after the crisis began because the site is too hostile to explore.
Developed by Hitachi-GE Nuclear Energy Ltd. and the International Research Institute for Nuclear Decommissioning, the robot is equipped with a camera, a thermometer and dosimeter.
Given the high radiation, it can only function for about 10 hours before the electronics fail, the institute said.
The robot will be remotely guided from a plant building where radiation is lower. About 40 workers will be involved and radiation exposure will be limited to 2.5 millisieverts or lower per person per day.