Abstract

The corrosion behaviors of SiC/SiC composite constituent materials in pure water at operating conditions, such as 300 °C and 8.5 MPa, were studied for potential application in accident-tolerant light water reactor (LWR) fuel cladding and core structures. Five kinds of SiC fibers, four kinds of SiC matrices, and three kinds of fiber/matrix interphase materials were examined in autoclaves. The potential constituent materials for future use in SiC/SiC composites were selected by considering corrosion rates and residual strength characteristics. The mass changes and the residual strength of each specimen were measured. SEM images of the surface layers were also inspected. The SiC fibers, regardless of their purity, crystallinity or stoichiometric ratio, decreased in strength due to the hydrothermal corrosion. For its part, the hydrothermal corrosion resistance of CVD-SiC, as a SiC matrix, was found to be affected by manufacturing conditions such as raw material gas type and synthesis temperature, as well as post-machining morphology. The CVD-carbon (CVD-C), as a fiber/matrix interphase material, showed good hydrothermal corrosion resistance. In order to protect the SiC fibers and the SiC matrices from hydrothermal corrosion, it would appear to be necessary to apply a dense CVD-C coating to both every fiber and the entire surface of the SiC matrices.

Highlights

  • Fiber-reinforced ceramic matrix composites are some of the most promising materials for high-temperature structural applications

  • Recent high-profile events, such as the incident at the Fukushima Daiichi nuclear power plant, have turned attention to SiC/SiC composites as potential candidates for structural materials to be used in accident-tolerant fuel (ATF) systems of light water reactor (LWR) applications [4,5,6,7,8,9,10,11]

  • In order to reduce the probability of such hydrogen explosions in the future, SiC/SiC composites are being seriously considered for their effectiveness and accident tolerant properties [6,7,8]

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Summary

Introduction

Fiber-reinforced ceramic matrix composites are some of the most promising materials for high-temperature structural applications. Recent high-profile events, such as the incident at the Fukushima Daiichi nuclear power plant, have turned attention to SiC/SiC composites as potential candidates for structural materials to be used in accident-tolerant fuel (ATF) systems of light water reactor (LWR) applications [4,5,6,7,8,9,10,11]. In the incident at the Fukushima Daiichi nuclear power plant, the oxidation of metallic components in high-temperature steam generated hydrogen and caused the explosion of the reactor building. Toshiba has started designing materials for applying the SiC/SiC composites to the accident-tolerant LWR fuel cladding and core structures and has been developing process technologies for thin-walled and elongated

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