The nuclear sector, as a pivotal provider of clean energy, plays a crucial role in advancing green economies. This sector is currently experiencing a resurgence, particularly with the recent emphasis on small modular reactors (SMRs), signaling a significant momentum toward nuclear energy expansion. However, ensuring the safety of nuclear facilities remains critical for the responsible deployment of this technology. Radiation Shielding Ultra-High-Performance Concrete (RS-UHPC)—an advanced type of concrete engineered for optimal packing density to enhance mechanical properties and durability while effectively attenuating radiation—emerges as a promising solution for reinforcing the Defense in Depth (DiD) strategy in nuclear infrastructure. Nevertheless, the existing understanding of RS-UHPC is limited and dispersed. By the writing of writing this review, the authors are unaware of any comprehensive review on the subject. This study aims to fill this gap by providing a thorough review of RS-UHPC formulations, critically analyzing existing literature, and identifying key RS-UHPC ingredients and mixture design techniques that influence RS-UHPC properties. Research priorities were identified to further advance RS-UHPC formulation, focusing on specific enhancements in mechanical, durability, and radiation shielding performance. The findings summarized herein contribute to a deeper understanding of the RS-UHPC compositional domain and mix design approaches, ultimately facilitating the achievement of desirable RS-UHPC performance and enhancing the DiD of nuclear facilities.
