The treatment of dependent failures in availability analyses

This short article will contribute to the development of an easy and handy formula, which enables instrumentation and control (I&C) practitioners to estimate conservatively the contribution of dependent failure to the overall unavailability of the integrated hardware-software safety-critical I&C-system. The desired formula fits in the existing methodology to quantify the unavailability of redundant hardwired I&C-sy stems. The methodology has been approved by licensing experts of nuclear facilities in Germany for two decades.