Overview of the European supercritical-water-cooled small modular reactor concept

This paper presents the European Supercritical-Water-Cooled Small Modular Reactor (SCW-SMR) concept developed within the ECC-SMART project, a joint European-Canadian-Chinese initiative. The 290 MWth reactor operates at 25 MPa with a core outlet temperature of 500 °C, achieving 44 % net thermal efficiency. The innovative horizontal fuel-assembly arrangement with seven heat-up stages and intermediate mixing plenums enables fully passive decay heat removal through natural circulation, even without operator intervention or external power for >72 hours. The compact pressure vessel (4.17 m inner diameter) contains 400 fuel assemblies in a 20×20 square lattice. System-level safety analyses demonstrate that all design-basis accidents are mitigated exclusively by passive systems, eliminating the need for high-pressure injection. The large subcooled water inventory and unique in-vessel natural circulation patterns limit peak cladding temperatures to <625 °C in normal operation and <780 °C during accidents. By integrating the high efficiency of supercritical-water cooling with inherently safe, fully passive features, the ECC-SMART SCW-SMR offers a promising Generation IV solution tailored to European energy and safety requirements.