Mechanical and Shielding Performance of Heavy-Density Concrete for Light Water Reactors Exposed to Elevated Temperatures

Light water reactors (LWRs) operating at temperatures around 300°C pose a challenge to structural concrete integrity. The high temperature induces compound changes in LWR structures compromising mechanical properties and initiation of cracks due to the degradation of structure. Concrete degradation within the reactor core can result in harmful radiation leakages, posing a significant threat to humans and the environment. Currently, gamma rays are attenuated using lead walls, which itself has limitations. These limitations include high density (difficult to work on), high cost, and toxicity. This experimental study aimed to develop heavy-density concrete suitable for nuclear power plants operating at 300°C by incorporating dolerite and magnetite aggregates. Dolerite aggregates were incorporated replacing normal aggregates at 25%, 50%, 75%, and 100% levels, while 25% of fine aggregate was replaced by magnetite in all concrete mixes. Control specimens were also prepared for comparative analysis. The concrete specimens were subjected to temperatures of 100°C, 200°C, and 300°C. Slump values, fresh and hardened densities, density loss, compressive strength, and nondestructive testing were performed for pre- and post-heated concrete specimens. Scanning Electron Microscope analysis, x-ray radiography, and gamma-ray attenuation measurements were also measured, including linear and mass attenuation coefficients, half-values, and tenth value layer. The findings indicate that the HMD3 concrete specimens, incorporating 75% dolerite and 25% magnetite aggregates, demonstrated superior mechanical properties with a 19.5% increase in compressive strength and minimal density loss. Significant improvements in the mass attenuation coefficient were observed, measuring 0.064 g/cm2 at 200°C and 0.067 g/cm2 at 300°C. Based on the results, this study recommends the utilization of dolerite aggregates in structural concrete for nuclear power plants and gamma irradiation facilities operating at a temperature of 300°C. This study highlights the potential of dolerite and magnetite aggregate radiation shielding concrete composite for LWRs.