[en] The analysis of the available experience as reported in collection of events related to safety and availability of reactor operation allows to verify the data and the hypothesis used in reliability analysis and contributes to detect common mode failures. The study used as an example in this paper is related to the PWR Residual Heat Removal System. The quantitative analysis of the reported events (essentially based on American reactors) permits an estimate of the probability of a total loss of the system which was found to be 0.10 per reactor-year, after interpretation of the experienced incidents according to the French RHR (Residual Heat Removal System) system design. The reliability study performed for this system, using fault tree analysis and Markov method, has led to a similar quantitative result