Fracture strength and principal stress fields during crush testing of the SiC layer in TRISO-coated fuel particles

• Published in: Journal of nuclear materials Vol. 477; no. C; pp. 263 - 272
• Main Authors: Davis, Brian C., Ward, Logan, Butt, Darryl P., Fillery, Brent, Reimanis, Ivar
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.08.2016; Elsevier
• Subjects: Asphericity; Compression tests; Crush test; Crush tests; FCM; FEA; Finite element method; Fracture mechanics; HTGR; Mathematical models; Methodology; SiC; Silicon carbide; Strength; TRISO; TRISO; FCM; FEA; HTGR; SiC; Strength; Crush test
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2016.05.018

Diametrical compression testing is an important technique to evaluate fracture properties of the SiC layer in TRISO-coated nuclear fuel particles. This study was conducted to expand the understanding and improve the methodology of the test. An analytic solution and multiple FEA models are used to determine the development of the principal stress fields in the SiC shell during a crush test. An ideal fracture condition where the diametrical compression test best mimics in-service internal pressurization conditions was discovered. For a small set of empirical data points, results from different analysis methodologies were input to an iterative Weibull equation set to determine characteristic strength (332.9 MPa) and Weibull modulus (3.80). These results correlate well with published research. It is shown that SiC shell asphericity is currently the limiting factor of greatest concern to obtaining repeatable results. Improvements to the FEA are the only apparent method for incorporating asphericity and improving accuracy. •A continuous stress vs. force function is defined by modifying the analytic solution.•FEA simulations with nonlinear geometry show improvements over analytic solutions.•During the test there are three different stress regimes defined by divot size.•SiC asphericity is a likely cause of numerical results deviating from empirical data.•Modeling true shell geometry is the factor of greatest concern in improving accuracy.