A new framework for multi-hazards risk aggregation

•The importance of communicating the level of trustworthiness for DM is demonstrated.•A framework is developed to assess the level of trustworthiness of PRA models.•DST-AHP method is used to implement the developed framework.•The weighted posterior method is used to consider the trustworthiness in MHRA.•An application to a case study is provided to show the feasibility of the framework. In this paper, we develop a new method for Multi-Hazards Risk Aggregation (MHRA). A hierarchical framework is first developed for evaluating the trustworthiness of the risk assessment. The evaluation is based on two main attributes (criteria), i.e., the strength of knowledge supporting the assessment and the fidelity of the risk assessment model. These two attributes are further broken down into sub-attributes and, finally, leaf attributes. The trustworthiness is calculated using a weighted average of the leaf attributes, in which the weights are calculated using the Dempster Shafer Theory-Analytical Hierarchy Process (DST-AHP). Risk aggregation is, then, performed by a “weighted posterior” method, considering the level of trustworthiness. An application to the risk aggregation of two hazard groups in Nuclear Power Plants (NPP) is illustrated.