Monday, July 25, 2011
With valves and pipes being allowed to leak up to 20 times their original limits by the Nuclear Regulatory Commission (NRC), according to a recent Associated Press report, smarter robotic inspectors are being proposed to detect underground leaks before they release radiation into groundwater.
More than three-quarters of aging U.S. nuclear reactors have leaked radioactive tritium from underground pipes at one time or another, according to the Associated Press, which recently concluded a year-long study. In response, Massachusetts Institute of Technology has designed a tennis-ball shaped robot to inspect underground pipes for cracks before they can contaminate groundwater.
Since the earliest nuclear reactors were built in the 1960s, more than 400 accidental radioactive leaks have been reported, according to the AP study, which maintains that over and over again, the safety standards set by the Nuclear Regulatory Commission (NRC) have been relaxed in order to allow reactors to continue operating, rather than making the costly repairs to bring reactors back into compliance. As a result, the danger of radioactive contamination of groundwater is increasing, according to MIT.
"We have 104 reactors in this country [and] 52 of them are 30 years or older," said MIT professor Harry Asada, director of MIT’s d’Arbeloff Laboratory for Information Systems and Technology. "We need immediate solutions to assure the safe operations of these reactors."
A spherical robot equipped with a camera is being proposed to navigate underground pipes at nuclear reactors to locate potential cracks that could leak radioactive water. (Source: MIT)
Groundwater contamination has already occurred at many nuclear reactor sites, where underground pipes carry water to cool reactor vessels, leaching radioactive tritium into the soil around them. Unfortunately, the U.S. Government Accountability Office reports that the industry has only very limited methods to monitor these underground pipes for leaks. Instead of direct inspections, today nuclear engineers depend on ultrasonic waves to reveal cracks, and induced voltage gradients to measure corrosion on pipe coatings. If any anomalies are detected, the only way to inspect the pipes now is to dig them up.
The new spherical robot designed by MIT aims to provide a way to directly inspect these underground pipes without digging, namely by navigating them from the inside to check of cracks and signs of corrosion. The tennis-ball shaped robot, designed by Asada and colleagues at MIT's d’Arbeloff Laboratory, can withstand the extreme radioactivity within the pipes and carries a video camera and transmitter to send back images that can be inspected by engineers to determine their condition.
To insure that the robot could navigate the pipes without getting stuck inside, its design was made free from external appendages or propellers. Instead, the smarter propulsion method harnesses the pressure of the water flowing through the reactor, re-channeling it to provide thrust. Tiny channels and valves within the skin of the robot switch the direction of liquid flow internally so that it is emitted as a jet on the opposite side of the desired direction for the robot to move.
Though still in the prototype stage, the researchers are also working on a camera pan and tilt mechanism powered by internal water flows. The camera itself will be fixed in position, but an internal two-axis gimbal will rotate the sphere in place to any desired direction.
Posted by R. Colin Johnson at 12:25 PM