Effects of Cr/Zircaloy-4 coating qualities for enhanced accident tolerant fuel cladding. (August 2023) - Ridley, Mackenzie
Highlights: Magnetron sputtered Cr coatings on Zircaloy-4 provide increased resistance to cladding rupture during simulated LOCA. Defects in Cr coatings can inhibit resistance to cladding rupture. Crack-free Cr coatings on Zry-4 show similar rupture temperatures as predicted for uncoated Zry-4 with ∼78% thicker cladding walls. Abstract: Cr-coated zirconium alloys represent a modern approach to enhance cladding safety during accident scenarios. Two high-power impulse magnetron sputtered Cr-coated Zry-4 systems were subjected to simulated loss-of-coolant accident conditions to investigate cladding performance. The first Cr-coating (4.8 µm thick) was deposited onto Zry-4 cladding and exhibited through-thickness cracking while the second Cr-coating (6.8 µm thick) was deposited with improved deposition parameters onto polished Zry-4 and exhibited no cracking. During burst testing, the coating with a higher density of defects failed to consistently reduce oxidation and exhibited similar burst behavior as Zry-4. In contrast, the second Cr-coating reduced ZrO2 formation through formation of Cr2 O3 and displayed enhanced burst temperatures by ∼80 °C compared to Zry-4. Utilizing an empirical relation for burst behavior of zirconium alloys, the 6.8 µm Cr/Zry-4 system displayed enhanced burst temperatures equivalent to an effective 0.464 mm increase in Zry-4 wall thickness, highlighting the value of continuous Cr coatings for accident scenarios.