Nanocrystalline diamond protects Zr cladding surface against oxygen and hydrogen uptake: Nuclear fuel durability enhancement


 In this work, we demonstrate and describe an effective method of protecting zirconium fuel cladding against oxygen and hydrogen uptake at both accident and working temperatures in water-cooled nuclear reactor environments. Zr alloy samples were coated with nanocrystalline diamond (NCD) layers of different thicknesses, grown in a microwave plasma chemical vapor deposition apparatus. In addition to showing that such an NCD layer prevents the Zr alloy from directly interacting with water, we show that carbon released from the NCD film enters the underlying Zr material and changes its properties, such that uptake of oxygen and hydrogen is significantly decreased. After 100–170 days of exposure to hot water at 360 °C, the oxidation of the NCD-coated Zr plates was typically decreased by 40%. Protective NCD layers may prolong the lifetime of nuclear cladding and consequently enhance nuclear fuel burnup. NCD may also serve as a passive element for nuclear safety. NCD-coated ZIRLO claddings have been selected as a candidate for Accident Tolerant Fuel in commercially operated reactors in 2020.

Polycrystalline diamond (PCD) layer protects Zr alloy nuclear rods from significant oxide formation and embrittlement at simulated accident conditions (elevated temperatures, hot steam). Carbon from PCD layer contributes to a formation of zirconium carbides which reduces the overall oxidation rate of Zr alloy.

Contact person: Irena Kratochvílová, +420 266 052 524, krat [at] fzu [dot] cz

Cooperating institutions:

  • Czech Technical University in Prague, Faculty of Mechanical Engineering, Technická 4, Prague 6, CZ-160 07, Czech Republic
  • RCPTM, Joint Laboratory of Optics of Palacký University in Olomouc, Institute of Physics, Czech Academy of Sciences, 17. listopadu 12, Olomouc, CZ-771 46, Czech Republic
  • University of Chemistry and Technology, Power Engineering Department, Technická 3, Prague 6, CZ-166 28, Czech Republic
  • Nuclear Fuel Division, Westinghouse Electric Company, 5801 Bluff Road, Hopkins, SC 29209, United States
  • Westinghouse Churchill Site, 1332 Beulah Rd., Pittsburgh, PA 15235, United States
  • Research Centre Řež, Hlavní 130, Husinec-Řež, CZ-250 68, Czech Republic
  • Institute for Applied Materials (IAM), Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, 76344, Germany