2018 | AFC ACCOMPLISHMENTS 93 Modified burst tests of ATF cladding candidates with a novel optical metrology technique inform future in-pile transient testing of the cladding candidates’ mechanical response during the pellet-cladding mechanical interaction phase of the RIA. Project Description: The deformation and failure behavior of ATF cladding candidates during RIA relevant conditions must be addressed to ensure safe and reliable operation of ATF-installed LWRs.This study aims to support the design of the nuclear safety envelope for ATF cladding candidates in LWRs by performing out-of-pile transient tests.The out-of-pile transient tests investigate the mechanical behavior and failure characteristics of the ATF candidates under PCMI-like loading conditions at the strain-rates of postulated design- basis RIAs.This research benefits from the pulse-controlled modified burst test (MBT) instrument and a novel noncontact optical method for measuring mechanical strain.The MBT offers a uniform mechanical strain-driven loading that mimics PCMI, while pulse-control reproduces the pulse-widths ofTransient Reactor Test Facility (TREAT) (from ~50 to >100 ms), CABRI (~20 ms), and Nuclear Safety Research Reactor (~10 ms) integral tests.The novel optical metrology technique enables 360° observation of the tubes, and tracks deformation or failure.ATF cladding candidates, including heat-treated (aged) iron-chromium-aluminum (FeCrAl) alloys and continuous silicon carbide fiber and silicon carbide matrix (SiC/SiC) composite tube samples have been tested to understand the failure characteristics of these materials during RIA relevant conditions.