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Title: The effect of coupled wear and creep during grid-to-rod fretting

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Nuclear Engineering and Design
Additional Journal Information:
Journal Volume: 318; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-04 22:39:30; Journal ID: ISSN 0029-5493
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Citation Formats

Wang, Hai, Hu, Zupan, Lu, Wei, and Thouless, M. D. The effect of coupled wear and creep during grid-to-rod fretting. Netherlands: N. p., 2017. Web. doi:10.1016/j.nucengdes.2017.04.018.
Wang, Hai, Hu, Zupan, Lu, Wei, & Thouless, M. D. The effect of coupled wear and creep during grid-to-rod fretting. Netherlands. doi:10.1016/j.nucengdes.2017.04.018.
Wang, Hai, Hu, Zupan, Lu, Wei, and Thouless, M. D. 2017. "The effect of coupled wear and creep during grid-to-rod fretting". Netherlands. doi:10.1016/j.nucengdes.2017.04.018.
title = {The effect of coupled wear and creep during grid-to-rod fretting},
author = {Wang, Hai and Hu, Zupan and Lu, Wei and Thouless, M. D.},
abstractNote = {},
doi = {10.1016/j.nucengdes.2017.04.018},
journal = {Nuclear Engineering and Design},
number = C,
volume = 318,
place = {Netherlands},
year = 2017,
month = 7

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on April 21, 2018
Publisher's Accepted Manuscript

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  • Grid-to-Rod Fretting (GTRF) wear is currently one of the main causes of fuel rod leaking in pressurized water reactors. The Consortium for Advanced Simulation of Light Water Reactors (CASL) has identified GTRF as one of the Challenge Problems that drive the requirement for the development and application of a modeling and simulation computational environment for predictive simulation of light water reactors. This paper presents fretting wear simulation methodology currently employed by Westinghouse, a CASL industrial partner, to address GTRF. The required advancements in the computational and materials science modeling areas to develop a predictive simulation environment by CASL to addressmore » GTRF are outlined.« less
  • The wear of fuel rod cladding against the supporting structures in the cores of pressurized water nuclear reactors (PWRs) is an important and potentially costly tribological issue. Grid-to-rod fretting (GTRF), as it is known, involves not only time-varying contact conditions, but also elevated temperatures, flowing hot water, aqueous tribo-corrosion, and the embrittling effects of neutron fluences. The multi-stage, closed-form analytical model described in this paper relies on published out-of-reactor wear and corrosion data and a set of simplifying assumptions to portray the conversion of frictional work into wear depth. The cladding material of interest is a zirconium-based alloy called Zircaloy-4,more » and the grid support is made of a harder and more wear-resistant material. Focus is on the wear of the cladding. The model involves an incubation stage, a surface oxide wear stage, and a base alloy wear stage. The wear coefficient, which is a measure of the efficiency of conversion of frictional work into wear damage, can change to reflect the evolving metallurgical condition of the alloy. Wear coefficients for Zircaloy-4 and for a polyphase zirconia layer were back-calculated for a range of times required to wear to a critical depth. Inputs for the model, like the friction coefficient, are taken from the tribology literature in lieu of in-reactor tribological data. Concepts of classical fretting were used as a basis, but are modified to enable the model to accommodate the complexities of the PWR environment. Factors like grid spring relaxation, pre-oxidation of the cladding, multiple oxide phases, gap formation, impact, and hydrogen embrittlement are part of the problem definition but uncertainties in their relative roles limits the ability to validate the model. Sample calculations of wear depth versus time in the cladding illustrate how GTRF wear might occur in a discontinuous fashion during months-long reactor operating cycles. A means to account for grid/rod gaps and repetitive impact effects on GTRF wear is proposed« less
  • One significant concern in the operation of light water nuclear reactors is the fretting wear damage to fuel cladding from flow-induced vibrations. For years, research on the grid-to-rod fretting (GTRF) phenomena has been underway in countries where nuclear power production is a significant industry. Under the auspices of the U.S. Department of Energy Consortium for Advanced Simulation of Light Water Reactors, an effort has been underway to develop and test an engineering wear model for zirconium alloy fuel rod cladding against a supporting grid. Furthermore, the multi-stage model accounts for oxide layers and wear rate transitions. Our paper describes themore » basis for a GTRF engineering wear model, the physical significance of the wear factor it contains, and recent progress toward model validation based on a fretting wear testing apparatus that accounts for coolant temperature, pressure, and the presence of periodic impacts (gaps) in grid/rod contact.« less