Software Helps Remote Robot Maintain Generators, Cut Downtime

Staff -- Control Engineering, 1/1/1998

When you measure downtime in thousands of dollars per minute, reliability and good maintenance become practically priceless. Unfortunately, knowing this doesn't make it any easier to get inside a nuclear reactor's pressurized steam generators to inspect, clean, and maintain its pipes and tubes.

That's why Foster-Miller Inc. (Waltham, Mass.) developed Cecil, one in a series of maintenance robots for steam generators. Cecil uses hardware and software from Opto 22 (Temecula, Calif.) to control its robotic inspection and cleaning functions.

"The reliability and capability of the hardware, and the single source, integrated FactoryFloor software running on a Microsoft Windows NT platform allowed us to migrate to a stable and very functional Windows development environment," says Dan Foley, Foster-Miller's control system engineer.

Before in-bundle, systematic, remotely controlled inspection devices became available, the suspected bad tubes were plugged or sleeved based only on primary-side eddy current inspections. Cecil overcomes these obstacles because it's inserted through the steam generator's inspection hand hole and moves to any point in the lower tube bundle along a monorail temporarily installed in the blowdown lane. An operator in a remote low-radiation area uses Cecil's color video probe and light source to inspect the tube bundle, monitor high pressure water cleaning of sludge by its flexible lance, and document "before" and "after" conditions.

The robot has evolved over several years and is now used as a secondary-side maintenance tool in nuclear plants worldwide. Foster-Miller reports that utilities using Cecil have fewer forced outages, reduced maintenance, less personnel radiation exposure, and prolonged steam generator life.

All of Cecil's analog and digital control signals, and sensor feedback for support equipment and water process functions, originate in an Opto 22 PC-based control system. Cecil's 100 or more optically-isolated intelligent I/O devices control all system functions. These devices are given tagnames by OptoControl, Opto 22's flowchart-based control language, which is part of the FactoryFloor suite.

Several flowcharts are then developed to control specific robotic functions and support systems, such as locomotion, lance and barrel motion, and water process functions. The flowcharts are then downloaded to and executed by an Opto 22 controller near the steam generator's hand hole. Joystick devices, interfaced with the controller and motion controllers via a serial port, provide the basic motion capabilities for each robot axis. The OptoControl language includes a library of serial functions integrated with standard analog, digital, logic, math, and host communications commands.

"It's easy to split a design into parts that best suit a person's area of expertise. Let controls people work with the flowcharting, let network people work with OptoServer and OptoConnect; and let others develop the human interface in OptoDisplay, Visual Basic, etc.," adds Mr. Foley.

For more information about Foster-Miller and Cecil, ; for more information about Opto 22, visit www.controleng.com/info.