Investigating grid-to-rod fretting wear of nuclear fuel claddings using a unique autoclave fretting rig

Sladjan Lazarevic, Roger Y. Lu, Cyrille Favede, George Plint, Peter J. Blau, Jun Qu

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

Fuel rods in a pressurized water nuclear reactor (PWR) experience coolant flow-induced relative motion against the grid support features, a phenomenon called grid-to-rod fretting (GTRF), which may cause progressive fretting wear damage. Wear-through of the cladding on fuel rods will leak the radioactive fuel into the coolant loop to significantly increase the radiation level in PWR primary loop and often trigger expensive Post Irradiation Examination. In this study, a unique autoclave fretting test rig was designed and fabricated to allow studying GTRF using actual cladding and grid materials. Water temperature was up to 220 °C, which was designed to mimic the environment in an industry full-assembly reactor core simulator. The contact load (0.1–1 N), oscillation frequency (20–30 Hz) and stroke (50–150 µm), and work rate (1–3 mW) were defined based on simulations of GTRF in an actual reactor. Using this autoclave GTRF rig, tests were conducted to learn the effect of water temperature and to investigate the wear behavior of different cladding-grid material combinations currently used in actual PWRs, including Zr alloy claddings without and with pre-oxidation against Zr alloy and Inconel grids. Higher water temperature evidently increased the cladding wear, and pre-oxidation of the Zr alloy and/or using the Inconel grid effectively reduced the wear rate. Results were correlated with the data of a full-size industry reactor core simulator in terms of both wear rate and wear scar morphology.

Original languageEnglish
Pages (from-to)30-37
Number of pages8
JournalWear
Volume412-413
DOIs
StatePublished - Oct 15 2018

Funding

WEC is appreciated for providing the commercial cladding and grids for testing and VIPER information and data for comparison. The authors also thank K. Cooley and R. Parten from ORNL for assistance on machine setup and sample preparation. This research was supported by the Consortium for Advanced Simulation of Light Water Reactors ( http://www.casl.gov ), an Energy Innovation Hub ( http://www.energy.gov/hubs ) for Modeling and Simulation of Nuclear Reactors, U.S. Department of Energy.

Keywords

  • Autoclave
  • Grid-to-rod fretting (GTRF)
  • Inconel
  • Wear coefficient
  • Zirconium

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