In March of 2011, there was an earthquake northeast of Japan. The resulting tsunami flooded the emergency generators of the Fukushima nuclear power plant on the Japanese coast. Three of the nuclear reactors at the plant suffered catastrophic meltdowns and radioactive materials were released into the atmosphere. Japan immediately shut down all their nuclear power reactors.
Six years later, ground water contaminated with radioactive materials is still leaking out into the ocean off the coast of Japan. The Japanese nuclear fleet is being turned back on one reactor at a time. It is still not known exactly where the melted cores of the destroyed reactors are.
TEPCO, the Japanese company that owns and operated the Fukushima power plant has attempted to use robots to explore parts of the damaged plant that are too radioactive for human beings to enter.
Last February, TEPCO deployed a robot developed by Toshiba and the International Research Institute for Nuclear Decommissioning (IRID). They sent the robot into Unit 2 but were unable to reach the area directly under the PVC. It did gather useful information though.
In March of this year, TEPCO employed the PMORPH robot developed by Hitachi-GR Nuclear Energy and IRID. It had a dosimeter and a camera. The robot took readings at ten different points inside the Unit 1 PVC.
Unfortunately, the robots employed rapidly broke down under the onslaught of hard radiation in the destroyed reactors. Now TEPCO is at it again with a new underwater robot.
The new robot will be used to examine the primary containment vessel (PCV) of the Unit 3 reactor which was destroyed in the disaster. In 2015, TEPCO found that the Unit 3 PVC was filled with coolant to a depth of about twenty feet. The access port for the PVC is only five and a half inches in diameter. Any robot that is going to be inserted into the PVC has to be smaller than five and one half inches in diameter.
The general manager of Toshiba Corporation's nuclear energy systems and services division, said: "We have already developed remotely operated robots for inspections at Fukushima. In this case, we had to meet the specific challenges of limited access and flooding, in a highly radioactive environment. Working with the International Research Institute for Nuclear Decommissioning (IRID), we succeeded in developing a small robot with high-level radiation resistance, and through its deployment we expect to get information that will support the advance of decommissioning."
The new Toshiba robot is screw-driven. It is about five inches in diameter and about twelve inches long. It weighs about four and a half pounds. It has a video camera facing forward and a video camera facing backward. It has LED lights to provide illumination for the cameras. The robot is control by a wire that trails behind it. It should be able to withstand radiation of up to about 200 Sieverts.
The new robot will be deployed after operators are trained. It will be interesting to see if this robot will be able to withstand the hard radiation inside the PVC long enough to collect the needed information.
Toshiba – IRID robot:
