The IAEA facilitated the co-operation of research and development among its Member States on advancing the state-of-practice in uncertainty and sensitivity methodologies for severe accident analysis in water cooled reactors. The main objective was to consolidate the existing knowledge related to uncertainty propagation in severe accident analyses in boiling water reactors (BWRs), and to enhance the expertise of practitioners in this specialized field. This publication showcases contributions from eight institutions from seven Member States, detailing their utilized methods for uncertainty and sensitivity analysis in severe accidents for BWR designs.