This paper reviews the current state of research on radiation shielding ultra-high-performance concrete (RS-UHPC) for use in the nuclear sector. The authors highlight the growing importance of nuclear energy as a clean energy source, especially with the development of small modular reactors (SMRs). However, they emphasize that the safety of nuclear facilities is paramount, making RS-UHPC a promising solution. The paper explores various ingredients, including heavyweight aggregates, nanomaterials, and reinforcing fibers, that influence the properties of RS-UHPC. It also examines two common mix design approaches: the Modified Andreasen & Andersen (MAA) model and the Absolute Volume Method. Finally, the paper identifies key research needs for advancing RS-UHPC formulations, particularly focusing on enhancing neutron shielding, exploring sustainable supplementary cementitious materials, and investigating novel reinforcing fibers.