Editor's Note: This is part of IEEE Spectrum's ongoing coverage of Japan's earthquake and nuclear emergency.
A robotic aerial vehicle hovering at the crippled Fukushima Dai-ichi nuclear plant has captured close-up video and photos that reveal the extent of the destruction in greater detail than previously seen.
Tokyo Electric Power Co. (TEPCO), the plant's operator, is using a T-Hawk [photo below], a remote operated flying machine created by U.S. firm Honeywell, to get a closer view of the severely damaged reactors.
The T-Hawk, known as a micro air vehicle, or MAV, uses a ducted-fan propulsion system that allows it to hover in place like a helicopter and fly into tight spaces where other aircraft can't go.
Last Friday, TEPCO workers, with assistance from Honeywell employees trained to pilot the T-Hawk, used the vehicle to survey the reactor buildings of Units 1, 3, and 4. TEPCO released the images the next day.
"What these images show is that the magnitude of the hydrogen explosions was incredible," said Stewart B. Minahan, executive director of operations for the Nuclear Energy Institute, an industry group.
Minahan, who has 35 years of experience with boiling water reactors, say the images are "very clear," and although they don't provide any new insight into the disaster, they show details that he hadn't seen before.
One of the elements most clearly visible is a round yellow structure sitting on the operating floor of Unit 4. The structure, Minahan says, is the drywell dome, the top part of the reactor's containment structure. When a boiling water reactor is in refueling mode -- as it was the case with Unit 4 -- workers use a crane to remove the dome and place it over concrete blocks on the floor. It's also possible to see fuel-handling machines, used to move fuel from the reactor into spent fuel pools.
But he says no parts of the reactors themselves are visible. "In my opinion, it will be hard to see them," he says. "These buildings had multiple floors, which collapsed because of the explosions."
TEPCO has used manned helicopters, high-altitude drones, and ground robots to obtain images of the facility. But the T-Hawk, because pilots can hold it in place and use its camera to zoom in on features, is giving TEPCO a better look of damages in and around the buildings.
Developed as part of a DARPA project, the machine is currently used in Iraq and Afghanistan for surveillance, route planning, and other missions. It weighs in at 7.7 kilograms (17 pounds), and pilots can control it manually or set up autonomous flight paths from up to 9.6 kilometers (6 miles) away and for up to 40 minutes at a time.
Honeywell, based in Morris Township, N.J., said in a release that three of its employees have flown five missions so far, capturing hours of video and dozens of photos. There are two T-Hawk units flying in Fukushima and two as back-up. Honeywell said that, in addition to cameras, they are carrying radiation sensors, though TEPCO hasn't yet released any data from them.
Below, some of the images (all taken on April 15) made public:
Unit 3, roof of reactor building
Unit 4, upper side of spent fuel pool, reactor building
Unit 4, seashore side of reactor building
Unit 4, operation floor of reactor building 2
Below, videos taken on April 15 [Editor's note: TEPCO says the videos show Units 1, 3, and 4, but they appear to show only Unit 4; the videos have no audio]:
This story was updated April 21.
Images: TEPCO; Honeywell. Videos: TEPCO