Development of Cr-coated Zirconium Alloy Cladding for Enhanced Accident Tolerance

J. Bischoff (1) , C. Vauglin (1) , C. Delafoy (1) , P. Barberis (1) , D. Perche (1) , B. Guerin (1) , J.-P. Vassault (1) , J.-C. Brachet (2)

1 AREVA NP - Centre Technique (FRANCE)
2 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

During the Fukushima Daiichi accident in 2011 the fuel rods underwent the degradation stages of a severe accident, including the rapid oxidation of zirconium, which led on the one hand to the production of large quantities of hydrogen, and on the other hand to additional heat production. Reducing the susceptibility of the cladding to the high temperature oxidation in steam can improve greatly the accident tolerance of the cladding and thus help reduce the risk of core meltdown. The worldwide research and development effort of the fuel nuclear industry to increase fuel margins in severe accidents is referenced as the development of Enhanced Accident Tolerant Fuels (EATF). In this context AREVA NP, along with CEA and EDF, is developing, among others, a chromium (Cr) coating (5-20$\mu$m thick) on zirconium alloy cladding. The coating is deposited on the cladding surface by Physical Vapor Deposition (PVD) and forms a dense and adherent protective layer. It preserves the good mechanical behavior of the current cladding in normal operating conditions while significantly improving the oxidation behavior in accidental conditions. This behavior is being evaluated through out-of-pile corrosion and mechanical tests at the AREVA NP Technical and Research Centers. The corrosion behavior was evaluated through autoclave tests in both PWR water chemistry at 360°C and in 415°C steam to increase the corrosion kinetics. In both cases very small weight gain was measured on the order of 1mg/dm$^2$ and remains stable throughout the length of the tests. This development is a part of the worldwide AREVA NP effort to improve the accident tolerance of the fuel through several projects and partnerships, in both Europe and the USA. In the USA, AREVA NP is strongly involved in the Department of Energy (DOE) program whose goal is to insert EATF solutions in US Light Water Reactors (LWRs) by 2022. In Europe, AREVA NP is on one side developing two cladding solutions (Cr-coated zirconium and SiC/SiC composite sandwich cladding) with the CEA and EDF, and on the other side is forming a partnership with the Gösgen utility to irradiate some EATF concepts under representative Pressurized Water Reactor (PWR) conditions.

Mots clés: Cladding; Accident Tolerant Fuels (ATF); Cr-coating; Physical Vapor Deposition (PVD); Corrosion

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

J. Bischoff, C. Vauglin, C. Delafoy, P. Barberis, D. Perche, et al.. Development of Cr-coated Zirconium Alloy Cladding for Enhanced Accident Tolerance. Topfuel 2016 - Light Water Reactor (LWR) Fuel Performance Meeting, Sep 2016, Boise, United States. ⟨cea-02438699⟩