Design and Qualification Qf a Microprocessor Subcooled Margin Monitor

Abstract

To meet the new regulatory requirements set forth in NUREG-0578, a Subcooled Margin Monitor was designed and qualified. The monitor is a microprocessor based system using temperature and pressure process parameters to continuously calculate and display margin to saturation in the reactor coolant system. The monitor consists of a small digital display unit mounted on the main control panel and a remotely mounted calculat- or module. Both the panel mounted display and the calculator module were seismically and environmentally qualified in accordance with IEEE 323 - 1974 and IEEE 344 - 1975. At the panel mounted display, the operator may select a continuous indication of pressure or temperature margin to saturation. Additionally, the monitor actuates an alarm on low margin to saturation and can also actuate auxiliary equipment with independent contacts. Two independent analog margin signals are provided to permit data logging on the plant computer and on a strip chart recorder.