The IAEA facilitated collaborative research among its Member States, in advancing the state of the practice in uncertainty and sensitivity methodologies for severe accident analysis in water cooled reactors. The primary aim was to evaluate the uncertainty and sensitivity associated with severe accident calculations, particularly concerning the progression and consequences of accidents in a generic CANDU type nuclear power plant under a postulated station blackout scenario. Key parameters considered in these analyses included hydrogen generation, event timings, and the release of fission products into the environment. The resulting publication showcases contributions from three institutions across three Member States, providing insights into their methodologies for uncertainty and sensitivity analysis in severe accidents.