Probabilistic Safety Assessment/Probabilistic Risk Assessment (PSA/PRA) for new and advanced reactors is recognised as an important approach to achieve improved safety and performances of new nuclear power plant (NPP), comparing to the existing plants. However, the application of PSA to these reactors encounters concurrent challenges, which are slightly different for new or advanced reactors due to their development phases. The technical challenges of the PSA for new reactors, which are in the last phases of design and commissioning stage, typically within five to ten years of commencing power operations, include a lack of design detail, a lack of empirical data, and the possibility of failure scenarios that differ in character from those treated in PSAs for current reactors. These challenges can affect a variety of decisions (e.g. plant safety level assessment, defense in depth assessment and risk balanced concept etc.) The technical challenges of the PSA for more advanced reactors, which are in research stage or in the early phases of conceptual design, in addition to the above-mentioned aspects, also include the potential need to address very different systems and phenomenology. The ability of current PSA technology to support design decisions for such reactors, and the potential value of advanced methods have not been internationally assessed in recent times.