Research Papers

Development of Kinetic Models for the Long-Term Corrosion Behavior of Candidate Alloys for the Canadian SCWR

[+] Author and Article Information
G. Steeves

Department of Chemical Engineering,
University of New Brunswick,
15 Dineen Drive,
Fredericton, NB E3B 5A3, Canada
e-mail: graham.steeves@unb.ca

W. Cook

Department of Chemical Engineering,
University of New Brunswick,
15 Dineen Drive,
Fredericton, NB E3B 5A3, Canada
e-mail: wcook@unb.ca

1Corresponding author.

Manuscript received May 29, 2015; final manuscript received December 14, 2016; published online May 25, 2017. Assoc. Editor: Thomas Schulenberg.

ASME J of Nuclear Rad Sci 3(3), 031001 (May 25, 2017) (7 pages) Paper No: NERS-15-1101; doi: 10.1115/1.4035549 History: Received May 29, 2015; Revised December 14, 2016

Corrosion behavior of Inconel 625 and Incoloy 800H, two of the candidate fuel cladding materials for Canadian supercritical water-cooled reactor (SCWR) designs, was evaluated by exposing the metals to supercritical water (SCW) in the University of New Brunswick’s flow loop. A series of experiments were conducted over a range of temperatures between 370 °C and 600 °C, and the corrosion rates were evaluated as the weight change of the materials over the exposure time (typical experiments measured the weight change at intervals of 100, 250, and 500 h, with some longer-term exposures included). Scanning electron microscopy (SEM) was used to examine and quantify the oxide films formed during exposure and the corrosion mechanisms occurring on the candidate metals. Data from in-house experiments were used to create an empirical kinetic equation for each material that was then compared to literature values of weight change. Dissolved oxygen concentrations varied between experimental sets, but for simplicity were ignored since the effect of dissolved oxygen has been demonstrated to be a minor secondary effect. Activation energies for the alloys were determined with Inconel 625 and Incoloy 800 H showing a distinct difference between the low-temperature electrochemical corrosion (EC) mechanism and direct high-temperature chemical oxidation (CO). The results were modeled using these separate effects showing dependence on the bulk density and dielectric constant of the supercritical water through the hydrogen ion concentration.

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Fig. 1

Conceptual design of the Canadian SCWR and re-entrant fuel channel: (a) fuel channel and (b) fuel bundle

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Fig. 2

Schematic diagram and photo of UNB’s SCW test loop

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Fig. 8

Experimental and modeled corrosion rates of (a) I625 and (b) A800H

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Fig. 7

Arrhenius plot of I625 (a) and A800 (b) oxidation indicating separate oxidation mechanisms

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Fig. 6

SEM images of A800H at different temperatures: (a) 370 °C, (b) 400 °C, (c) 500 °C, and (d) 550 °C

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Fig. 5

SEM images of I625 at different temperatures: (a) 370 °C, (b) 400 °C, (c) 500 °C, and (d) 550 °C

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Fig. 4

800H experimental data results including the averaged mass change

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Fig. 3

I625 experimental data results including the averaged mass change




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