Quantitative Methods for Reliability and Fault Tolerance Testing of Digital Instrumentation and Control

Obsolescence, aging, reliability, and performance issues are driving nuclear facilities to replace conventional analog I & amp;C systems with digital technologies. The increased complexity of digital systems, compared to their analog counterparts, has resulted in faults that are often more difficult to detect, classify, and correct. Experience in the nuclear industry has shown that traditional software quality assurance processes should be improved to be more effective at discovering and rectifying these faults. The goal of this project is to develop a Software Reliability Tester (SRT) that will provide a means to quantify the reliability and fault tolerance of digital I & amp;C systems used in nuclear facilities. The SRT will include capabilities to 1) perform statistical testing on the digital I & amp;C to quantify its reliability before implementation, 2) systematically test and identify faults that were not tested in the design/development phase, and 3) establish warning signals/regions for when the plant instrumentation is outside of the normal range. The proposed SRT will dramatically reduce the validation time for the qualification testing by providing a quantifiable system reliability and fault tolerance assessment. The SRT will provide independent verification of reliability and fault tolerance before a digital system is implemented, and will help eliminate incidents of digital equipment malfunction during all stages of the equipment lifecycle. This is particularly important for vital plant services that affect public safety. This will greatly benefit the nuclear industry and the public by reducing the testing time, installation time, and downtime inherent in digital system upgrades, thus providing more reliable power generation and minimizing electricity costs to the public.