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Title: Microstructural characterization of a thin film ZrN diffusion barrier in an As-fabricated U–7Mo/Al matrix dispersion fuel plate

The United States High Performance Research Reactor Fuel Development program is developing low enriched uranium fuels for application in research and test reactors. One concept utilizes U–7 wt.% Mo (U–7Mo) fuel particles dispersed in Al matrix, where the fuel particles are coated with a 1 μm-thick ZrN coating. The ZrN serves as a diffusion barrier to eliminate a deleterious reaction that can occur between U–7Mo and Al when a dispersion fuel is irradiated under aggressive reactor conditions. To investigate the final microstructure of a physically-vapor-deposited ZrN coating in a dispersion fuel plate after it was fabricated using a rolling process, characterization samples were taken from a fuel plate that was fabricated at 500 °C using ZrN-coated U–7Mo particles, Al matrix and AA6061 cladding. Scanning electron and transmission electron microscopy analysis were performed. Data from these analyses will be used to support future microstructural examinations of irradiated fuel plates, in terms of understanding the effects of irradiation on the ZrN microstructure, and to determine the role of diffusion barrier microstructure in eliminating fuel/matrix interactions during irradiation. The as-fabricated coating was determined to be cubic-ZrN (cF8) phase. It exhibited a columnar microstructure comprised of nanometer-sized grains and a region of relatively highmore » porosity, mainly near the Al matrix. Small impurity-containing phases were observed at the U–7Mo/ZrN interface, and no interaction zone was observed at the ZrN/Al interface. The bonding between the U–7Mo and ZrN appeared to be mechanical in nature. A relatively high level of oxygen was observed in the ZrN coating, extending from the Al matrix in the ZrN coating in decreasing concentration. The above microstructural characteristics are discussed in terms of what may be most optimal for a diffusion barrier in a dispersion fuel plate application.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [3]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Centre de I'Energie Nucleaire, Boertang, Mol (Belgium)
Publication Date:
OSTI Identifier:
1177648
Report Number(s):
INL/JOU--14-31479
Journal ID: ISSN 0022-3115; TRN: US1500084
DOE Contract Number:
AC07-05ID14517
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Nuclear Materials; Journal Volume: 458; Journal Issue: C
Publisher:
Elsevier
Research Org:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; MICROSTRUCTURE; ZIRCONIUM NITRIDES; DIFFUSION BARRIERS; FCC LATTICES; HARDNESS; MELTING POINTS; Temperature Range 1000-4000 K; DENSITY; THERMAL EXPANSION; LATTICE PARAMETERS; THIN FILMS; STABILITY; CORROSION RESISTANCE; Electric Conductivity; FRICTION; Mechanical Properties; Thermodynamic Properties; Electrical Properties; Chemical Properties; DEPOSITION; OPTIMIZATION; FUEL PLATES; Dispersions IRRADIATION TESTING; NUCLEAR FUEL; RESEARCH REACTOR; URANIUM MOLYBDENUM ALLOY