Neutronic feasibility of civil marine small modular reactor core using mixed D2O+H2O coolant

•Neutronic Feasibility of soluble-boron-free civil marine SMR core has been investigated.•This study uses mixed D2O+H2O coolant and micro-heterogeneous duplex fuel.•Mixed coolant provides ∼21.5 years core life, a ∼40% increase in life than the H2O coolant.•Mixed coolant provides core lifetimes comparable to those of HEU naval vessels. In an effort to decarbonize the marine sector, there are growing interests in replacing the contemporary, traditional propulsion systems with nuclear propulsion systems. The latter system allows freight ships to have longer intervals before refueling; subsequently, lower fuel costs, and minimal carbon emissions. Nonetheless, nuclear propulsion systems have remained largely confined to military vessels. It is highly desirable that a civil marine core not to use highly enriched uranium, but it is then a challenge to achieve long core lifetime while maintaining reactivity control and acceptable power distributions in the core. The objective of this study is to design a civil marine core type of single batch small modular reactor (SMR) with low enriched uranium (LEU) (