Surface Modification of Zirconium Alloy with Nanocrystalline Diamond: Enhancing Quenching Performance for Accident Tolerant Fuel.

Nuclear energy remains a critical component of the global energy, yet its safety, particularly under extreme conditions, has been a major concern since the Fukushima Daiichi accident. Zirconium (Zr) alloys are widely used as fuel cladding in light water reactors due to their excellent nuclear properties, but their reaction with high-temperature steam during loss-of-coolant accidents(LOCA) poses a significant risk of hydrogen explosions. To enhance the accident tolerance of Zr alloy cladding, this article proposes a surface modification approach using nanocrystalline diamond (NCD) coatings to improve boiling heat transfer performance. High-temperature quenching experiments are conducted, supported by high-speed camera, scanning electron microscopy (SEM), and Raman spectroscopy. The results demonstrate that the NCD coating (1 µm thick) significantly enhances heat transfer performance: it reduces re-wetting time (12.33 s vs. 15.67 s, a 21.3% improvement), increases the maximum cooling rate (111.48 °C s-1 vs. 94.73 °C s-1, a 17.7% enhancement), and elevates the Leidenfrost temperature to 572.24 (15.06% higher than bare Zr alloy). Thermodynamic parameter calculations indicate that the NCD enhances heat transfer efficiency by improving the solid-liquid contact temperature parameter (kρc). Furthermore, Raman spectroscopy confirms the coating's stability. This article provides critical experimental and theoretical insights for developing accident tolerant fuel (ATF) claddings, offering significant implications for improving the safety of nuclear reactors.