Cannonball-like underwater robots being developed for nuclear reactors
By Ben Coxworth
July 21, 2011
According to the Associated Press, a recent study has revealed that three quarters of America's nuclear reactors have leaked radioactive tritium from buried pipes that transport water for the cooling of reactor vessels. This tritium could in turn find its way into the groundwater. While industry officials do reportedly check these pipes for leaks, they can only do so in either indirect or costly, labor-intensive manners. Now, however, researchers from MIT are developing tiny, spherical swimming robots that could check on the pipes directly, relaying their findings in real time.
Using present technology, the easiest ways of looking for leaks include applying an electrical current to pipes to check for corrosion, or applying ultrasonic waves to identify cracks. These methods are both indirect, however, and could potentially miss things. The only truly direct approach is to dig the pipes up and look at them, which is obviously a very involved process.
The egg-sized MIT robots would be placed inside the pipes and move through them, observing their inner surfaces with a built-in video camera, and transmitting live images up to 100 meters (328 feet) via a laser optic system.
Because protruding propellers or rudders could cause the robots to get stuck, they would instead be propelled simply by harnessing the existing flow of the water. They would be steered using a series of Y-shaped valves in their outer skins, that connected to a network of tiny internal pipelines. Selectively opening and closing theses valves would determine which pipelines the water could flow into and jet out of, taking advantage of a phenomenon known as the Coanda effect. This jetting action would control the direction in which the robots moved.
The researchers are also developing a system that would allow the camera to pan and tilt. This would be achieved through a two-axis gimbal inside the robot, that would shift its mass back and forth and up and down, thus allowing it - and the camera - to face in any direction on command.
Pipes filled with radioactive material are not a friendly environment, needless to say, so the robots are being designed with the assumption that they would only last for a few missions before needing to be replaced. They could nonetheless be performing a very valuable service.
"We have 104 reactors in this country," said MIT's Harry Asada, a professor of engineering. "Fifty-two of them are 30 years or older, and we need immediate solutions to assure the safe operations of these reactors."