Length Dependence of Severe Accident Test Station Integral Testing

The safety of accident-tolerant fuel (ATF) candidates must be tested under simulated loss-of-coolant accident (LOCA) conditions to evaluate their improved safety margins. This evaluation eventually must include testing of irradiated materials. This report describes the fiscal year (FY) 2019 activities to (1) improve the information yield of integral design–basis LOCA tests by using digital image correlation (DIC) calculations on the engraved specimens’ surfaces and (2) to investigate the effects of reducing the length of nuclear-grade FeCrAl specimens tested in the Severe Accident Test Station (SATS) to improve the costeffectiveness of irradiation campaigns for future work. Analysis showed the DIC technique to be effective at calculating strains, and that specimens as short as 4 inches could be used for LOCA experiments while maintaining similar balloon and burst behavior as 12-inch specimens. With these results, an irradiation vehicle design effort was initiated to encapsulate multiple 4-inch thin-walled tube cladding specimens and test them under irradiation in the flux trap of the High Flux Isotope Reactor. By utilizing thermal modeling and optimizing the design parameters, calculated specimen temperatures were predicted to vary less than 2% during irradiation. Future work is planned to finalize the design and safety basis approvals and initiate a HFIR irradiation in support of in-cell integral LOCA tests at the Irradiated Fuels Examination Laboratory (IFEL).