In 2019, the International Atomic Energy Agency launched a coordinated research project titled “Advancing the State of the Practice in Uncertainty and Sensitivity Methodologies for Severe Accident Analysis in Water Cooled Reactors of CANDU Types.” This project involved participation from 22 organizations representing 18 member states. The purpose of the project was to advance the understanding and characterization of the sources of uncertainty and assess their impacts on key water-cooled reactor figures of merit predicted by severe accident (SA) codes. Three organizations from three member states participated in the CANada Deuterium Uranium (CANDU) exercise: Canadian Nuclear Laboratories, Canada; Korea Atomic Energy Research Institute, Republic of Korea; and University Politehnica of Bucharest, Romania. Each contributor used its own SA code and uncertainty analysis tools and selected its own uncertain input variables with associated probability distributions. All three participants performed a station blackout scenario for a generic CANDU 6 station, using similar normal operating conditions and analysis assumptions. This paper presents the results of the uncertainty and sensitivity calculations from each contributor and discusses the key findings, lessons learned, and future work.