Nuclear reactors operate under some of the most extreme conditions found in industrial engineering, combining intense radiation fluxes with corrosive coolants and high temperatures. The structural materials used in reactor cores, primary cooling systems, and containment structures must maintain integrity over decades of service. Protective coatings are a critical line of defense, shielding components from degradation that could compromise safety, increase maintenance costs, or shorten plant lifespan. Over the past two decades, coating technologies have evolved from simple corrosion barriers to sophisticated multifunctional systems tailored for nuclear environments. This article examines the latest innovations in coating materials and methods, their benefits and limitations, and the research directions that promise even more resilient solutions for the next generation of nuclear power plants.

The Nuclear Reactor Environment: A Demanding Setting for Materials

To appreciate the role of coatings, one must first understand the aggressive conditions inside a nuclear reactor. The primary coolant loop—whether light water, heavy water, or liquid sodium—carries heat away from the fuel assemblies but also promotes corrosion of metal surfaces. In water-cooled reactors, radiolysis produces oxidizing species like hydrogen peroxide, which accelerate general and localized corrosion. In sodium-cooled fast reactors, oxygen impurities and mass transport effects can cause corrosion and carburization. Meanwhile, high-energy neutron and gamma radiation induce displacement damage and transmutation within coating and substrate materials, altering their mechanical and chemical properties. Temperatures in pressurized water reactors (PWRs) reach around 320 °C, while in boiling water reactors (BWRs) they are slightly lower but still aggressive. Advanced reactors, such as very high-temperature reactors (VHTRs), push toward 900–1000 °C. The combination of thermal stress, radiation, and chemical attack demands coatings that can adhere firmly, maintain chemical stability, and self-