CrN–NbN nanolayered coatings for enhanced accident tolerant fuels in BWR
Journal article, 2023

The accident tolerant fuel (ATF) concept has emerged in the years after the 2011 Fukushima accident as part of a renewed effort in research for light water reactors. The primary focus is to further improve safety measures under and beyond design basis accident conditions, and to improve fuel cladding performance in normal operation. The application of a coating on zirconium claddings can achieve both these aims without extensive changes to the reactor design. Metallic chromium coatings have been profusely studied as solution for pressurized water reactors, but the search for an effective ATF coating able to withstand the environment inside boiling water reactors (BWRs) is still ongoing. In this work, two different versions of a novel nitride coating composition were studied. Zirconium claddings coated with 8 µm thick layers of superlattice CrN–NbN and a nanolayered CrN–NbN were tested in autoclave under BWR operating conditions for 60 days. Scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, electron back-scattered diffraction, x-ray diffraction, and atom probe tomography were employed to characterize as-deposited and autoclaved samples of these two materials. During exposure, both coating versions formed a stable, dense and passivating oxide scale (200–300 nm thick) on the surface, demonstrating improved oxidation protection under operating conditions. Some differences in the oxide growth mechanism were observed between the superlattice and the nanolayered CrN–NbN coatings, which allowed to glimpse at the effect of the layer thickness on the oxidation protection provided by these coatings. The nano-structured morphology of both coatings remained unaffected by the autoclave test, but a 35 nm thick Zr-Cr-N phase was found at the coating-substrate interface of the superlattice CrN–NbN coated cladding.

Accident tolerant fuels

Nitride coating

CrNNbN

Atom probe tomography

Superlattice

PVD

Author

Andrea Fazi

Chalmers, Physics, Microstructure Physics

Mohammad Sattari

Chalmers, Physics, Microstructure Physics

Michal Strach

Chalmers, Physics, CMAL

Torben Boll

Karlsruhe Institute of Technology (KIT)

Marta Krystyna Stiller

Chalmers, Physics, Microstructure Physics

Hans-Olof Andrén

Chalmers, Physics, Microstructure Physics

Denise Adorno Lopes

Westinghouse Electric Company

Mattias Thuvander

Chalmers, Physics, Microstructure Physics

Journal of Nuclear Materials

0022-3115 (ISSN)

Vol. 586 154681

Superior Accident Tolerant Fuel via Enhanced Technology (SAFETY)

Swedish Foundation for Strategic Research (SSF) (EM16-0031), 2018-02-01 -- 2023-01-31.

Subject Categories

Energy Engineering

Manufacturing, Surface and Joining Technology

Materials Chemistry

Corrosion Engineering

DOI

10.1016/j.jnucmat.2023.154681

More information

Latest update

9/5/2023 1