This CRP aims to harmonise international understanding of ex-vessel corium behaviour and cooling (EVCC) during severe accidents in water-cooled reactors. It will consolidate experimental and plant data, enhance modelling and simulation, conduct benchmark exercises including accident management scenarios, and develop training resources for capacity building. Motivated by key IAEA meetings and reinforced by expert input from leading research institutes and national programs, the CRP addresses a high-priority R&D topic with strong Member State support. By providing a harmonized technical basis, it will support accident management strategies across diverse reactor designs.