The pipes at nuclear power plants are dangerous places -- with very hot water, high pressure, high radioactivity.
Today, stationary sensors provide some insight into conditions inside the pipes. But as the nation's nuclear fleet ages, engineers need to see more.
Researchers at the Massachusetts Institute of Technology are working to improve remote imaging of the piping at pressurized water reactors with the development of tiny, spherical robots that could work their way through them and send video images back to watchers in a control room.
That could help operators find leaks and address a concern raised by the Government Accountability Office in June. GAO said all U.S. nuclear plant sites have experienced leakage of potentially radioactive water into the ground, some of it likely from buried pipelines that are hard to access and inspect for cracks (E&E Daily, June 22).
Harry Asada, a mechanical engineering professor and director of MIT's d'Arbeloff Laboratory for Information Systems and Technology, is aiming to address the problem with the development of a robot the size of a billiard ball that could withstand the pipes' harsh environment, travel wirelessly and transmit data on what it sees.
"We have 104 reactors in this country," Asada said. "Fifty-two of them are 30 years or older, and we need immediate solutions to assure the safe operations of these reactors."
Asada, working with two graduate students, is testing prototypes for a device that would be smooth on the exterior to avoid getting trapped in tight spaces and minimize the risk of breaking pieces off the sensors and other instrumentation already housed within the pipes.
Anirban Mazumdar, a doctoral student working on the propulsion system, said the team's approach has been to design the robot with interior chambers that can fill up with water, then spit that out in one direction or another to push the robot along the pipe.
"The definition of a robot implies a bunch of things -- in this case it's not going to be autonomous; it's going to be controlled by a person, but it's going to move," Mazumdar said.
Wireless controls -- used both to handle the long distances that must be traveled and to minimize the potential for entanglement on existing pipeline sensors -- would let the user speed the robot along straightaways and then slow it down to maneuver in tight spaces, he said.
Another graduate student, Ian Rust, is working on an "eyeball" system that would let the robot change the orientation of the internal camera without moving its shell.
The final model must be robust enough to handle the environment for limited periods, but low-cost enough to be disposable when it succumbs to radiation exposure and relatively easy to dispose of as contaminated waste.
So far, the team has been making larger-scale mock-ups of the various mechanisms at play, fine-tuning the parts, Mazumdar said. Inspiration has come from other devices used for aquatic imaging. "We've certainly derived some lessons from underwater robots that are used for inspecting seabeds and things like that," he said.
This summer, the team hopes to assemble functional prototypes of the robots at roughly the target size. Mazumdar said a finished robot might be one to two years away.
At that point, the team could try to spin the idea off into a company or work with the nuclear industry from within MIT. "The ideal dream is that [nuclear companies] would come to us" for the technology, Mazumdar said.
MIT has a strong track record of supporting researchers seeking to turn their work into commercial success -- a record that other universities seek to emulate, in hopes of fostering an ecosystem of startups, tech companies and venture firms like that in the Boston area.
Mazumdar emphasized that the approach Asada's team is taking would be one of many tools that nuclear operators could use to monitor plant conditions. "The nuclear industry is really very well developed, and I don't want it to seem like we've revolutionized everything with this," he said.
But the robots aim to fill a gap in the industry's arsenal, Mazumdar said. "The project really came to us because [the industry was] faced with a unique challenge that they couldn't solve with the tools available to them."