Influence of microstructure on hydrothermal corrosion of chemically vapor processed SiC composite tubes

Abstract

Multi-layered SiC composites consisting of monolithic SiC and a SiCf/SiC composite are one of the accident tolerant fuel cladding concepts in pressurized light water reactors. To evaluate the integrity of the SiC fuel cladding under normal operating conditions of a pressurized light water reactor, the hydrothermal corrosion behavior of multi-layered SiC composite tubes was investigated in the simulated primary water environment of a pressurized water reactor without neutron fluence. The results showed that SiC phases with good crystallinity such as Tyranno SA3 SiC fiber and monolithic SiC deposited at 1200 degrees C had good corrosion resistance. However, the SiC phase deposited at 1000 degrees C had less crystallinity and severely dissolved in water, particularly the amorphous SiC phase formed along grain boundaries. Dissolved hydrogen did not play a significant role in improving the hydro-thermal corrosion resistance of the CVI-processed SiC phases containing amorphous SiC, resulting in a significant weight loss and reduction of hoop strength of the multi-layered SiC composite tubes after corrosion. (C) 2017 Elsevier B.V. All rights reserved.