In the framework of the Organisation for Economic Co-operation and Development/Nuclear Energy Agency PREMIUM [Post-BEMUSE (Best-Estimate Methods Uncertainty and Sensitivity Evaluation) REflood Model Input Uncertainty Methods] benchmark (2012–2015), Tractebel has contributed to the development and the proof-of-concept application of a sampling-based inverse uncertainty quantification (IUQ) approach with the DAKOTA statistical uncertainty and sensitivity analysis tool. This IUQ approach has been applied to quantify the RELAP5/MOD3.3 reflood-related model input uncertainties, based on selected reflood tests [FEBA (Flooding Experiments with Blocked Arrays) and PERICLES]. This paper presents the Tractebel IUQ approach as well as the results of applications to the PREMIUM benchmark. Lessons learned and perspectives for future development are also discussed.