The application of plasma assisted chemical vapour deposition of ZrC onto a Zr-alloy substrate

Abstract

Zirconium alloys are widely used as fuel cladding materials in Light Water Reactors (LWR) due to their excellent mechanical properties and low neutron absorption. The incident that occurred at Japan’s Fukushima Daiichi nuclear power plant was aggravated by the lack of resistance of the zirconium alloy, as fuel rod cladding exposed to steam oxidation produces explosive hydrogen. Thus, the improvement against oxidation of Zr alloy fuel cladding by coatings, such as, silicon carbide (SiC) and zirconium carbide (ZrC) has become an area of interest. This study investigated available literature on the deposition of ZrC using various coating methods in order to find and apply a feasible method to apply ZrC that is cost effective. This study applied a Radio Frequency cold plasma assisted chemical vapour deposition method using a set of parameters, in an effort to coat ZrC on a mild steel substrate (instead of Zr alloy substrate) followed by the use of Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) to characterise the coated product. The results obtained showed that a sufficient ZrC layer was not deposited on the substrates. This is attributed to inadequate vacuum and or the leak of oxygen to the reactor. Further studies using a different range of parameters of the cold plasma chemical vapour deposition method used is recommended to improve on the deposition characteristics and determination of the feasibility of ZrC coating on Zr alloy fuel cladding materials