TEST METHODS FOR HOOP TENSILE STRENGTH OF CERAMIC COMPOSITE TUBES FOR LIGHT WATER NUCLEAR REACTOR APPLICATIONS

摘要

The US DOE plans to replace conventional zirconium-alloy fuel rod tubes in light water reactors (LWR) with those consisting of ceramic matrix composites (CMC) thereby enhancing fuel performance and accident tolerance of LWRs. Silicon carbide fiber-reinforced silicon carbide-matrix (SiC/SiC) composites demonstrate tolerance to the irradiation and chemical environments of LWRs. Loss of gas tightness and mechanical integrity due to the build-up of internal gas pressure and the swelling of fuel pellets are among the anticipated failure modes for the LWR fuel cladding. Therefore, rigorous determination of the hoop tensile (or equivalent) strength properties is critically important for evaluation of SiC/SiC CMC fuel claddings. Because there are no commonly-accepted design methodologies for advanced composite tubular components, there are limited mechanical test standards for any properties of tubular ceramic composite components. Therefore, some current and proposed test methods for measuring tensile hoop strength of composite tubes are presented, discussed, and compared for application to CMCs. Proposed standard test methods are presented in terms of the following experimental issues - test specimen geometries/preparation, test fixtures, test equipment, interferences, testing modes/procedures, data collection, calculations, reporting requirements, and precision/bias.