Proving absence of CCFs: A case for Open Source

Common cause failures have emerged as the major issue in licensing digital I&C systems. It is easy to use farfetched scenarios to argue that there is a possibility that all redundancies will fail at the same time. The difficulty of countering such arguments has led to the introduction of various kinds of diversity, which increases both complexity and costs of the solutions. Risk-informed arguments can be used to show that selected scenarios are unlikely and not worth considering. This opportunity has not been used in actual projects due to obstacles for carrying out a detailed analysis. This situation would change if the target applications were built on Open Source solutions. The paper investigates some approaches to this problem when both the source code and its development history are available. More generally the paper argues that Open Source can offer the nuclear industry many benefits, especially when aiming at reusing earlier engineering solutions.