[en] The objective of the Instrument Calibration and Monitoring Program (ICMP) is to offer an alternative to meeting current instrument calibration requirements and provide a method of enhanced monitoring for redundant instrument channels. The ICMP methodology utilizes computer software to non-intrusively monitor data from redundant instrument channels and incorporates this data with a limited number of technician field calibrations to verify the accuracy and performance of monitored instrumentation. By eliminating unnecessary field calibrations and associated labor, a decrease in personnel radiation exposure and labor costs will be realized, and the potential for miscalibration due to human error will be reduced. The ICMP was developed and tested at Northeast Utilities' Millstone Unit 2 nuclear power plant. The prototype system was interfaced to the plant process computer in January 1989. The system was installed at South Carolina Electric and Gas Company's Virgil C. Summer Station during the September 1991 refueling outage. In both installations, the ICMP was able to identify instrument channels that deviated by more than the acceptance criteria and were therefore candidates for field calibration