UHT Test Facility Updates and Oxidation Tests for Accident Tolerant Fuel Development

Abstract Research and development on accident tolerant fuel (ATF) have been widely pursued by the nuclear industry around the world. Westinghouse is developing new accident tolerant fuel design, EnCore® Fuel. Chromium (Cr) coated zirconium alloy and silicon-carbide (SiC) fuel cladding are the excellent candidates for application in fuel cladding of light water reactors (LWRs)[1, 2]. The ATF fuel is being developed to deliver beyond-design-basis (BDB) and design-basisaltering (DB) safety margins, withstanding far more severe conditions than the current fuel. The products in this portfolio have enhanced temperature performance enabling survival during BDB and DB accidents. The products also minimize interactions of fuel and fuel rod materials with water. The Cr-coated zirconium alloy cladding exhibits sustained high temperature performance and inhibits the detrimental effects of the zirconium-steam reaction. Westinghouse’s silicon-carbide (SiC) fuel cladding offers safety benefits in severe accident conditions, particularly compared to the significant hydrogen-and-heat producing reactions that occur above 1200° C for zirconium fuel cladding. These advancements will increase safety margins and enable the transition to high burnup facilities as well. To support the accident tolerant fuel (ATF) development, the Westinghouse Ultra High Temperature (UHT) test facility was built at the Westinghouse Churchill site in early 2016. The UHT test facility has been upgraded recently. The current UHT reactor was designed to promote better sealing of the reaction chamber and a smaller uncertainty on cladding temperature measurement. Simulating large break LOCA steam conditions, the UHT oxidation tests have been performed with SiC Optimized ZIRLO® and Cr-coated zirconium alloy cladding. In the EnCore Fuel program, one of the key tasks is to test the safety features and margin gain of the EnCore Fuel. This paper describes the designs, safety features and baseline commissioning tests for the upgraded Ultra High Temperature (UHT) test facility.