RIA simulation tests using driver tube for ATF cladding

Abstract

Pellet-cladding mechanical interaction (PCMI) is a potential failure mechanism for accident tolerant fuel (ATF) cladding candidates during reactivity-initiated accident (RIA). This report summarizes Fiscal Year 2017 (FY17) research activities to evaluate the PCMI-like hoop strain-driven mechanical response of ATF cladding candidates. To achieve various RIA-like conditions, a modified-burst test (MBT) device was developed to produce different mechanical pulses. The calibration of the MBT instrument was accomplished by performing mechanical tests on unirradiated Gen-I FeCrAl alloy samples. Shakedown tests were also conducted in both FY16 and FY17 using unirradiated hydrided ZIRLO tube samples. This milestone report focuses on testing using ATF materials, but the benchmark tests with hydrided ZIRLO tube samples are documented in a recent journal article . For these calibration and benchmark tests, the hoop strain was monitored using strain gauges attached to the sample surface in the hoop direction. A novel digital image correlation (DIC) system with mirrors was developed for MBT instrument to better resolve the failure behavior of the sample and provide useful data for validation of high-fidelity modeling and simulation tools. The DIC system includes one high-speed camera and six mirrors which enable a 360°-view of the sample’s outer surface. This feature was added to the instrument to determine the precise failure location on the sample surface for strain predictions. The DIC system was tested on several silicon carbide fiber/silicon carbide matrix (SiC/SiC) composite tube samples at various pressurization rates of the driver tube (which corresponds to the strain rate on the sample). The hoop strains for various loading conditions were determined for the SiC/SiC composite tube samples. Future work is planned to enhance understanding of the failure behavior of the ATF cladding candidates of age-hardened FeCrAl-alloys and SiC/SiC composites in detail during RIA conditions informed by the computational studies performed under the Advanced Fuel Campaign (AFC). The testing instrument and the new DIC system will be further developed to reach different stress-state conditions with capability to perform tests at elevated temperatures.