SYMPOSIA PAPER Published: 28 July 2021
STP162220190014

The Behavior of Cr-Coated Zirconium Alloy Cladding Tubes at High Temperatures

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In the frame of Framatome’s “PROtect” enhanced accident tolerant fuel development program, different solutions are being investigated to improve the fuel rod’s resistance to accidental conditions. The near-term solution is a dense and adherent chromium coating applied to zirconium (Zr) alloy cladding by the physical vapor deposition technique. The main advantage of the coating is a significant reduction in the high-temperature steam oxidation that occurs under design basis accident and beyond design basis accident conditions, which leads to decreased hydrogen and heat production. However, at high temperatures, the formation of the zirconium-chromium (Zr-Cr) eutectic at approximately 1,330°C is a key point in beyond design basis accident conditions with regard to the cladding integrity and thus needs to be investigated. In this work, Cr-coated cladding samples were first characterized after high-temperature oxidation (1,000°C) and the protecting effect of the Cr coating against steam oxidation was investigated. Coated samples were also characterized after rapid heating (up to 100°C/s) in an inert atmosphere to temperatures of around 1,500°C. Electron microscopy and electron backscatter diffraction were used to identify the different phases present in the samples and to get better insight on the eutectic formation characteristics in the coated cladding. The formation of the Zr-Cr eutectic at the surface of the coated cladding was confirmed, which resulted in consumption of the Cr coating. At temperatures above ~1,330°C and within inert atmospheres, the Cr coating is consumed through two competing mechanisms: the diffusion of Cr into the Zr cladding, which remains in solid solution, and the formation of the Zr-Cr eutectic.

Author Information

Chaari, Nermine
Framatome, Lyon, FR
Bischoff, Jeremy
Framatome, Lyon, FR
Buchanan, Karl
Framatome, Lyon, FR
Delafoy, Christine
Framatome, Lyon, FR
Barberis, Pierre
Framatome, Ugine, FR
Augereau, Julien
Framatome, Paimboeuf, FR
Nimishakavi, Kiran
Framatome, Lynchburg, VA, US
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Details
Pages: 189–210
DOI: 10.1520/STP162220190014
ISBN-EB: 978-0-8031-7691-1
ISBN-13: 978-0-8031-7690-4