Snake let loose in reactor

On paper, Ringhals AB's problem was no big deal: the Swedish company had to replace a section of stainless-steel pipe that was part of a safety system activated when its nuclear reactor went offline in an emergency. This CAD image shows the pipe in a Swedish nuclear reactor that needed repairs, along with obstacles in the way. 's problem was no big deal: the Swedish company had to replace a section of stainless-steel pipe that was part of a safety system activated when its nuclear reactor went offline in an emergency. But there was no physical line of sight to the 8-in.-diameter pipe and the largest access path was a 3.5-in.-wide, 31.5-in.-high corridor. The pipe is one of 157 spaced 4 in. from each other and running floor to ceiling along the edge of a circular room, nicknamed the Jungle, beneath the reactor core. Only three companies bid on the project, and two wanted to cut away enough pipes in the Jungle to make a human-sized path. But there was no guarantee the pipes could be replaced, which meant the 800-MW reactor would have to shut down. The winning bid from however, relied on snake-arm robots from Scanning the Field for Ideas Snake-arm robots are composed of stacked circular sections operating much like a human spine. Controlled sections attach to three actuators via three wires. The wires and other hardware connections are inside the sections, so the external surface is smooth. Software working at 350 Hz with a CANenabled servoamp controller calculates how much the actuators must push or pull to twist the robot into the desired shape. The robot can carry 22 lb at its tip and has three operating modes. Joystick path-following lets operators drive the tip by viewing a tip-mounted camera, and the computer forces the rest of