The operational complexity index: A new method for the global assessment of the human factor impact on the safety of advanced reactors concepts

With the increasing reliability of the modern technology, the human contribution to the global risk in the operation of industrial systems is becoming more and more significant: in the nuclear reactor operation, for example, a recent Probabilistic Safety Assessment of this contribution is about 25% of the probability of core damage, all situations considered.This urges the designers of future nuclear reactors to consider the minimization of this Human Factor (HF) contribution, at the very early stage of their design: the experience feedback shows that this is indeed at this stage that the fundamental design options, most impacting the human reliability in operation, are fixed.The problem is that at these early design stages, it is also quite impossible to apply formal human reliability methods to support this HF optimisation, while the precise operating conditions of the reactor are not yet known in enough details.In this paper, another approach of the HF evaluation is presented. This method for the early assessment of the HF impact on the plant safety is proposed for the comparison of various advanced reactor concepts currently being designed within the frame of the international GENERATION IV initiative.