Assessment of Pre-irradiation SiC CMC Joint Performance in Representative Cladding Geometries

摘要

Silicon carbide fiber reinforced, silicon carbide matrixcomposites (SiC-SiC) offer strength at high temperatures,corrosion resistance, and stability during irradiation, andare being developed by General Atomics as cladding foraccident tolerant fuel (ATF) applications and advancedreactor concepts. Advanced joining techniques capable ofwithstanding harsh reactor environments are key to enableGA’s SiGAtm SiC-SiC composite. The objective of this workis to obtain joint-specific material properties for assembliesin representative planar and cladding geometries that willallow for the generation of a material properties databaseand more accurate simulation of SiC joint behavior across arange of temperatures and irradiation conditions. Tosupport this, three different joint formulations are beingassessed for mechanical and thermal performance pre andpost irradiation in the High Flux Isotope Reactor (HIFR) atORNL. GA has previously identified its hybrid SiC (HSiC)joint as the most promising and best suited joining approachfor cladding applications . Additionally, oxide and transeutecticphase (TEP) joints are being investigated to makethe material property database more comprehensive asthese joints have previously shown strength resilience underirradiation in planar geometries . The thermal andmechanical data obtained in this work will address vitalknowledge gaps, enabling more accurate modeling of jointsin SiC-based components for accelerated materialqualification.The scope of work presented here focuses on themechanical and thermal performance of the joint materialprior to irradiation in HFIR. Endplug push-out (EPPO)testing to determine joint strength in tube geometries, andshear strength testing for planar geometries have provideda benchmark for pre-irradiation mechanical performance.These results show that all three selected jointmethodologies result in cladding joints capable ofwithstanding the expected joint stresses in a LWR reactorenvironment . This has been accompanied by He leaktesting of the joint regions on tube specimens to assess thesuitability of each joint methodology for claddingapplications. Here, only the HSiC formulation consistentlymet critical leak rate requirements suggesting that otherjoining strategies require additional development. Finally,pre-irradiation thermal testing has been completed toestablish a baseline for comparison after irradiation.Subsequent irradiation of these joints types in HFIR willprovide further detail on joint material properties and theirappropriateness for nuclear applications.