| Abstract Scope |
Zirconium alloy cladding used in BWRs faces degradation risks under high-temperature and radiolytic water chemistry conditions, including oxidative corrosion, hydroxide formation, and radiation-assisted damage. Conventional chromium coatings, while effective under pressurized water reactor (PWR) conditions, tend to form soluble Cr (OH)3 under BWR-specific electrochemical potentials, leading to long-term instability.
To address this, we have developed a multilayered ceramic/metal barrier coating system optimized for BWR environments. The architecture comprises alternating layers of an Yttrium–Aluminum oxide ceramic and a CrY alloy, deposited over Zircaloy-4 substrates. The system leverages the intermediate hydroxide stability and thermodynamic resilience of the Yttrium–Aluminum oxide phase, which offers greater resistance to aqueous degradation than pure Y2O3 or Cr2O3.
High thermal stresses resistance was evaluated through cyclic exposures at 800–900 °C in air, followed by rapid quenching. Multilayer-coated tubes exhibited no spallation, visible cracking, or scale formation even after 10 thermal cycles, while uncoated tubes showed surface fracturing and swelling. To further evaluate coating integrity under accident scenarios, Loss-of-Coolant Accident (LOCA) tests will be conducted at Oak Ridge National Laboratory (ORNL). These tests will assess the coating’s high-temperature mechanical survivability, oxidation kinetics, and structural stability under rapid thermal transients, providing critical data for performance under extreme reactor events.
This work highlights a promising pathway for next-generation fuel cladding protection in BWRs, enabling enhanced operational safety margins and informing future autoclave and in-reactor testing protocols. The insights gained could support the design of more robust fuel systems and contribute to long-term performance improvements under accident-tolerant fuel development initiatives. |