Associate Professor Keiji Nagatani (center) with his collaborators, Professor Satoshi Tadokoro (right) and Associate Professor Kazunori Ohno (left), Graduate School of Information Sciences (GSIS), Tohoku University
On 11th March, 2011, a massive earthquake and accompanying tsunami hit the Tohoku region of eastern Japan. The result was that Fukushima Daiichi Nuclear Power Plants faced a crisis because of loss of all power, setting the stage for meltdowns. It was very dangerous for humans to enter the nuclear reactor buildings to conduct damage assessment due to radioactive materials.
We checked the radiation tolerance of electronic components in our mobile rescue robot, called Quince, with irradiation tests at Japan Atomic Energy Agency (JAEA); our commercial electronic devices worked more than 100 h at a 10% safety margin in the target environment (100 mGy/h), without any lead shielding. Next, we tested the wireless communication function for operating Quince under such environments, including at Hamaoka Daiichi Nuclear Power Plants, which indicated that robust wireless communication was not possible in reactor buildings due to thick concrete. We thus adopted a wired communication system (wire length: 500 m). The wire was reeled out as the robot goes forward and rewound upon moving backward. Finally, we mounted surveillance devices such as dosimeter on it. While such preparations were ongoing, prospective robot operators from Tokyo Electric Power Company (TEPCO) trained under mock-up setting.
At last, one of the robots was delivered to the Fukushima on 20th June, 2011, and it contributed significantly to surveillance missions at the plant. One of the biggest successes in the missions was that TEPCO came to understand the health of the core spray plant and its low dose rate in building #3. After the mission, the plant was re-activated immediately by workers to cool the reactor core directly. We still have much research issues to improve the robot, so we will continue research on remotely-operated mobile robot technologies.
Keiji Nagatani, Satoshi Tadokoro, et al, "Emergency Response to the Nuclear Accident at the Fukushima Daiichi Nucl ear Power Plants using Mobile Rescue Robots", Journal of Field Robotics, Volume 30, Issue 1, pp.44-63 (2013-01)