Autonomous drones developed at San Antonio-based Southwest Research Institute may penetrate the hazardous, radiation-laden reactors of the Fukushima Daiichi nuclear power plant in Japan.
The plant suffered a catastrophic disaster, and multiple reactor meltdowns, after a massive earthquake hit the coast of Japan causing a massive tsunami in 2011. Since then, the Tokyo Electric Power Company Holdings Incorporated have been responsible for clean up.
Radiation in the Fukushima plant is so high, a single dose — one-fiftieth its strength based on some 2017 readings — would be fatal in weeks.
In addition to radiation, these tethered ground-based units have had to deal with reactors containing falling water, unpredictable walkways and obstructions.
"It's because of these numerous technical challenges, almost seven years after the earthquake and tsunami, there's still little or no information about the current state of some of the areas within these damaged reactors,” said Monica Garcia, the project manager for the Southwest Research-led team that included expertise from the University of Pennsylvania’s General Robotics, Automation, Sensing and Perception lab.
Representatives from the Tokyo Electric Power Company Holdings Incorporated approached SwRI about the possibility of flying drones two years ago. The idea was that self-flying drones would bring back data that eluded ground-based robotics.
“Investigations had issues with objects on the walkway, and walkways that had shifted,” Garcia said. “Unmanned aerial systems are not constrained to moving on that walkway.”
SwRI began work on the project in February.
The drones had to be autonomous because there was no way to control the units by radio frequency, said SwRI technical lead Richard Garcia, who is married to project leader Monica Garcia.
“It’s a building, in a building, in a building, in a building,” he said describing the reinforced concrete walls. “The idea we would lose wireless communication was almost guaranteed.”
Ground-based drones were controlled via wired tether, something too cumbersome for a lightweight flying drone.
Another difference between ground and air units was a building philosophy, Monica Garcia said.
The ground units were reinforced to endure the grueling radiation that affects the cameras and navigation systems. The aerial units were built with off the shelf components, and custom autonomous software, but without any additional shielding.
“Adding shielding, just adds weight,” said Richard Garcia, adding that aerial units are meant to travel and assess quickly. They have a flight time of 10-15 minutes, and aren’t intended to come back from inside the reactors, he said.
SwRI built and successfully tested the drones for Tepco Holdings late last year. It tested the drones with radiation levels multiple times higher than what they expected to encounter. Since no one has readings from inside some of these reactors, it is unclear how high the radiation may go.
SwRI continues in talks with Tepco about next steps.
Paul Flahive can be reached at email@example.com or follow him on Twitter @paulflahive