Fault tree linking versus event tree linking approaches: a reasoned comparison

Two well-known modelling approaches are in use in probabilistic risk assessment: fault tree linking and event tree linking. The question of which modelling approach is most appropriate for specific applications has been extensively, if not emotionally, debated among experts in the past two decades, addressing both modelling and quantification issues. In this article, we determine their degree of equivalence and build ‘methodological bridges’ between the two approaches from a mathematical and algorithmic perspective. We show that, under certain conditions, both modelling approaches are equivalent. Since both fault tree linking and event tree linking approaches are subject to limitations and approximations, established bridges make it possible to formulate important recommendations for probabilistic risk assessment practitioners and quantification engine developers.