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Boston Dynamics‘ Spot robot has been helping the decommissioning team at the Fukushima Daiichi nuclear plant to survey the site of the disaster and plan for the future.
It’s been more than a decade since the 2011 Fukushima nuclear disaster, but much of the areas remain unexplored today. For example, some rooms have doors that have been shut since the disaster, and officials weren’t sure what to expect on the other side of these doors.
In 2022, the decommissioning crew at the plant began using Spot to collect data, shoot video, measure radiation dose, and gather debris samples for radiation testing. This effort required a robot to navigate difficult terrain, carry substantial weight, open and close doors, and collect analysis samples, according to Koji Watanabe, Deputy Manager of 2nd Mechanical Equipment Group of the Decommissioning Division of Nuclear Power Plant of Tokyo Power Technology (TPT).
This is a high bar for a robot to pass, and Spot’s unique capabilities gave it the edge over other robots the team had used, which include tracked and wheeled robots, according to Brad Bonn, head of nuclear programs for Spot.
The challenges of decommissioning Fukushima
Full decommissioning of the Fukushima plant is expected to take several decades. Human exploration of the site is extremely dangerous and slow due to the precautions people must take in areas with high levels of radiation. Workers must wear large amounts of cumbersome personal protective equipment and observe strict limits on how much time they can spend in radioactive areas.
The worst areas in the plant are designated at LD50 or higher, meaning that a 30-day exposure would be lethal for half of the population. These areas cannot be entered by people at all and must be explored by robots. But robots also face challenges in these areas. Drones are not always ideal for this kind of work, as their rotor blades can kick up dust and debris, potentially spreading contaminated wheels, and robots with tracks or wheels often get caught up in debris.
The radiation at the site can also interfere with electronic systems by jumbling data in logical circuits or simply causing physical damage to circuitry. So, before Spot was brought to the site, Boston Dynamics had to test it to ensure it would be able to stand up to high levels of radiation.
To do this, the company brought Spot to Los Alamos National Laboratory. While the team could have outfitted Spot with lead protection, this would have added weight and placed limits on the amount of additional equipment the robot would be able to carry.
Initially, testers exposed Spot to 82 years’ worth of the allowable human dose of radiation, and by the end of the tests, the team tripled that amount. There were no adverse effects on Spot from any of the radiation, verifying it was ready to explore the Fukushima plant.
Spot at the Fukushima site
Spot’s goals at the site were to investigate the disaster, simulate necessary data for future decommissioning operations, and create a decommissioning archive. It was outfitted with the necessary equipment to shoot videos, measure radiation levels, obtain point cloud data, and collect samples for radioactivity analysis. While at the site, Spot used a lidar device to collect point cloud data, a mounted camera to shoot video, and its Spot arm to collect smear samples. Spot also used its arm to place mesh radios in appropriate locations around the site to facilitate better communications.
Operators controlled Spot remotely from a safe distance, but Spot’s autonomous capabilities still played a big role in the decommissioning. The robot plans every step it takes autonomously, meaning the operator simply has to tell it what direction to go in.
Additionally, Spot’s Arm opens doors mostly autonomously, a capability that makes it much faster than other robotic gripper arms. The operator only needs to tell Spot where the doorknob is and which side of the door the hinge is on, and Spot does the rest. This process is up to 10 or 20 times faster with Spot’s Arm than with other arms.
Yoichiro Naka, CEO of Tohoku Enterprise Co. (TECO), the Boston Dynamics Preferred Solution Partner that is assisting with the decommissioning effort, said that Spot’s data collection project ended in success. Spot completed its planned video shooting, radiation measurement, and gathering of point cloud data and analysis samples.
Spot’s work at the plant resulted in important insights. For example, Spot’s investigation revealed that windows in the operation room of one unit were broken and that the room was contaminated.
“There’s a mix of things that they’re going to use this information for,” Bonn says. “One is simply determining whether humans can go into specific spaces—and if so, for how long, and what protective equipment is going to be necessary. They may come up with a strategy to put shielding up to make safer areas, but they need this information first. There’s also the matter of prioritization: deciding how to go about the decommissioning process, and what needs to happen in which order.”
While it’s not clear what role exactly Spot will be playing in future decommissioning efforts, Bonn says he imagines it will have plenty to do. Spot could collect progress data by using lidar scans to monitor decommissioning over time. The robot will also likely be using its arms to clear away small debris, making it possible for larger unmanned machinery to conduct more intensive cleanup work.