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RBMK Maintenance
Alignment Equipment Improves Equipment Maintenance Capabilities

US Dept. of Energy
Office of International Nuclear Safety and Cooperation

1000 Independence Ave S.W.
Washington, DC 20585
(301) 903-0234

Each RBMK reactor relies on approximately 2,000 high-speed pumps and ventilators to operate safely. Many of these pumps supply cooling water to keep reactor fuel in a safe temperature range. If normal cooling water were lost suddenly, the reactor core could become dangerously hot, potentially cracking or melting the covering around the fuel and releasing highly radioactive materials. To minimize this possibility, a backup system of emergency pumps is kept on constant stand-by, ready to flood the fuel core with water until the reactor can be shut down safely and the problem corrected.

High-speed, rotating pump parts must be kept in precise alignment so that they perform as intended in normal and emergency situations. The slightest misalignment or imbalance of rotating pump machinery can lead to bearing and seal failure, resulting in degradation of equipment performance and premature failure. Misaligned pump shafts cause about 70 percent of pump failures in operating nuclear reactors in the United States. It is estimated that a similar figure applies in the former Soviet Union.

Through a program implemented by the U.S. Department of Energy, state-of-the-art vibration monitoring and shaft alignment systems are being provided to all RBMK reactor facilities: Chornobyl in Ukraine; Ignalina in Lithuania; and Leningrad, Smolensk and Kursk in Russia. The systems, significantly better than equipment currently in use, enable maintenance staff to detect, diagnose and correct misalignment and imbalance in rotating machinery.

The vibration monitoring system uses a hand-held computer that can upload data from a rotating machine. The system has superior computational ability that requires less operator training and enables operators to take measurements with greater accuracy than previously possible. This significantly reduces the possibilities of misdiagnosis and incorrect repair of the operating equipment.

Equipment also is being provided for precise shaft alignments, including computerized laser alignment tools. When mounted on the shaft of machines, the laser can detect a misalignment with high precision in a matter of seconds. The compact computer performs calculations, provides digital read-outs, and advises the operator on the adjustments necessary to properly align the equipment being tested. The information is recorded and stored in the analyzer and can be transferred easily to a personal computer.


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