Fukushima, Japan

A mock up of a transformable investigation robot has undergone testing at a lab. This robot, equipped with camera and dosemeter, plus thermometer, has been developed by IRID and Hitachi-GE Nuclear Energy, Ltd. to explore deep inside the PCV of Unit 1 and record the current conditions inside the vessel. This work is too hazardous for humans because of high radiation.

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Use of robots for reactor stabilization and decommissioning at Fukushima Daiichi NPS

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On March 11, 2011 Japan was literally rocked by a massive earthquake and tsunami that resulted in thousands of lives lost, homes and businesses destroyed, and a crippling of Japan’s nuclear power industry. It was a wakeup call clearing showing how unprepared Japan, and other countries that operate nuclear power plants, were when they need to deal quickly and decisively with a major disaster.

It quickly became apparent how ineffectual traditional equipment and methods are at dealing with this type of unexpected catastrophe. Damage to the nuclear facilities at Fukushima was extensive, and so severe that personnel couldn’t enter the damaged structures to even begin assessing the extent of the damage.

Over the past few years since the disaster, many research facilities and companies have worked hard to develop and deploy equipment that can be used in the event of any future disaster. One of the most promising is the autonomous drone system developed by Professor Kenzo Nonami of Chiba University, who is also the president of the spin-off Autonomous Control Systems Laboratory (ACSL).

The challenges they faced were immense. For example, in the event of a disaster it is likely that local communication and control systems will be damaged to the point that they are inoperable. Most nuclear facilities are metal structures that block access to GPS signals and preclude the use of FPV technology since they couldn’t assume that the necessary signals would penetrate the buildings. The internal environment, after the disaster, would be chaotic with fallen beams and debris everywhere. And, since people wouldn’t be able to enter the hazardous zone, the device would have to recharge itself.

One by one, they were able to address each of the major challenges. The autonomous drone system they are designing is equipped with a multitude of sensors including laser range finder, proximity, video, and others. As it explores the damaged zone it is able to 3D map all walls, debris, and other objects building a detailed representation of the area. Its sensors and programming also incorporate object detection and avoidance. So, if any unexpected barrier blocks its passage, the drone avoids and tries to find another path around the barrier.

The data transmission and power challenges were addressed by designing a sophisticated robotic docking station for the drone. Periodically, typically when its battery packs reach a preset lower limit, the drone returns to the docking station, centers itself, then lands. Automated mechanisms built into the base of the dock unplug depleted batteries and replace them with fresh cells. This is critical since the flight time for most typical drones is less than 30 minutes while battery packs can take hours to recharge. And, due to the radiation hazards, human beings cannot enter the hazard zone to manually replace the drones battery packs.

Needless to say, the system still needs some further development and testing before it can operate completely autonomously. In the current configuration, several operators watch over the drone and its docking station in operation closely.

Nevertheless, Professor Nonami and his team have successfully demonstrated the feasibility of their approach. It’s a rare occasion when we have the opportunity to observe this level of technology working so smoothly and effectively, achieving its design goals.

Hopefully, we will never face another disaster like the March 11, 2011 earthquake, tsunami, and nuclear incident. But, if we ever do, it’s comforting to know that projects like Professor Nonami’s drone will be there to support us in our moment of extreme need.

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Toshiba and IRID developed a robot to investigate PCV (Primary Containment Vessel) interiors of Fukushima Daiichi Unit No.2.

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"Small Robot Developed to Investigate Interior of Primary Containment Vessel of Fukushima Daiichi Nuclear Power Station Unit 2"

June 30, 2015

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Toshiba Corp. showed a device that will be used to pull fuel rod assemblies from the spent fuel pool inside reactor 3 building at the Fukushima No. 1 plant.

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A remote-controlled submersible has found what is likely to be the missing melted nuclear fuel from the 2011 Fukushima nuclear disaster.

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