A new reactor concept is described that directly couples a supercritical CO2 (sCO2) power cycle with aCO2-cooled, heavy water moderated pressure tube core. This configuration attains the simplification andeconomic potential of past direct-cycle sCO2 concepts, while also providing safety and power densitybenefits by using the moderator as a heat sink for decay heat removal. A 200 MWe design is describedthat heavily leverages existing commercial nuclear technologies, including reactor and moderator systemsfrom Canadian CANDU reactors and fuels and materials from UK Advanced Gas-cooled Reactors(AGRs). Descriptions are provided of the power cycle, nuclear island systems, reactor core, and safetysystems, and the results of safety analyses are shown illustrating the ability of the design to withstandlarge-break loss of coolant accidents. The resulting design attains high efficiency while employingconsiderably fewer systems than current light water reactors and advanced reactor technologies, illustratingits economic promise. Prospects for the design are discussed, including the ability to demonstrateits technologies in a small (~20 MWe) initial system, and avenues for further improvement of the designusing advanced technologies.