Assessing the Radiation Tolerance of 3C Silicon Carbide and Silicon Carbide Composites

  • Benjamin Clay

Student thesis: Doctoral Thesis

Abstract

The radiation response of 3C CVD SiC and two SiC/SiC composites have been assessed in nuclear reactor relevant conditions in order to find their suitability as nuclear materials for current Generation 2, and fusion power reactors. The MIAMI facilities have been used to irradiate 3C CVD SiC and SiC/SiC composites using ion beam systems with in-situ TEM so that the microstructural evolution of these proposed nuclear materials could be analysed whilst under irradiation to help understand the underlying mechanisms involved. This work shows for the first time, the nucleation of highly pressurised helium platelets forming within stacking faults in 3C CVD SiC, a defect that could potentially lead to crack formation in a reactor scenario. Two SiC/SiC composites, the first comprising of Tyranno SA3 fibres coated in PyC with a CVI SiC interface, and the second comprising of Hi-Nicalon Type S fibres with a C particle reinforced SiC matrix, were irradiated for the first time with a He ion beam capable of implanting He into the samples at the same rate per dpa as calculated for a pressurised water reactor. High radiation resistance was found for both composites at the PWR relevant temperature of 350oC as no microstructural changes were observed. At the fusion relevant temperature of 1000oC, the ORNL composite was also found to have high radiation tolerance up to the proposed upper limit of 200 dpa. With ahigh He implantation rate induced by a 15 keV He ion beam, the PyC interface within the ORNL sample was found to lose its crystallinity at 2 dpa, 400oC with a He concentration of 24,000 appm, a third of the concentration to be found in SiC during a PWI in a fusion reactor although no delamination of the PyC between the fibre or matrix occurred. SRIM calculations regarding the I-NERI Project PERSEUS have highlighted the low damage level of approximately 0.02 dpa where SiC has been seen to corrode in LWR relevant conditions suggesting that radiolysis products may have a bigger impact on corrosion than the direct damage induced in SiC via radiation.
Date of Award16 Nov 2024
Original languageEnglish
SponsorsEngineering and Physical Sciences Research Council
SupervisorGraeme Greaves (Main Supervisor) & Steve Donnelly (Co-Supervisor)

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