b'A dense Cr-coating on a zirconium- thermal conductivity. Variants of the based cladding substrate has thechromia-doped UO 2fuel pellet have potential for improved high temperaturebeen in development in the Framatome steam oxidation resistance and highGmbH Fuel Laboratory in Erlangen, temperature creep performance, as wellGermany (see Figure 1). Testing shows as improved wear behavior. Over thea significant increased thermal conduc-course of the EATF program, extensivetivity compared to UO 2 .processing and testing activities areIn-pile testing of new variants of being carried out in support of deliv- chromia-doped UO 2fuel is planned ering EATF Lead Test Assemblies (LTAs),in the Advanced Testing Reactor with two sets of LTAs successfully(ATR) at Idaho National Laboratory delivered in 2019, and support of batch(INL). A total of nine rodlets, which implementation by the mid-2020s. includes rodlets with standard UO 2Chromia-doped UO 2pellets canand two variants of chromia-doped improve pellet wash-out behavior afterUO 2will be irradiated to study the cladding breach and reduce fissionevolution of thermal conductivity gas release. To date, the performanceand microstructure under irradiation. of this fuel has been extensivelyTest rodlets were received by INL in studied in out-of-pile and in-pilethe third quarter government fiscalFigure 2. IrradiatedCr-coated tube after 21% test programs and modifications areyear (GFY) 2020. These fuel rods willdeformation at 350.being implemented to accommodatebe placed in an outer capsule that chromia-doped fuel in Framatomesprovides isolation from the reactor fuel performance code. water coolant. Capsules are scheduled For revolutionary (over-the-horizon)to be inserted for irradiation testing performance improvements,in ATR cycle 169A.Framatome is developing a compositeCoating adhesion plays a critical role cladding comprised of silicon carbidewhen considering the functional fiber in a silicon carbide matrix (SiC f / behavior of Cr-coated cladding. SiC) as well as studying applicationsThe adherence of the coating after for other critical components suchirradiation was confirmed through as BWR channel boxes and structuralExpansion Due to Compression (EDC) tubes. The objective is to develop atests performed by the CEA at 350C. fuel system which does not sufferThis type of test is representative of from the same rapid oxidation kineticsthe stresses imposed by the pellet on of zirconium-based cladding whilethe cladding but with much higher having attractive operating featuresdeformations. Figure 2 shows the such as reduced neutron absorptionirradiated sample deformed up to 21% cross-section and higher mechanicalwith no observed delamination of the strength at accident temperatures. Cr-coating. The apparent interfacial Accomplishments: stability and absence of delamination A major emphasis of Framatomes ATFclearly demonstrates that the coating pellet development has been improvingretains excellent adhesion.pellet thermal properties, especially 2020|AFC ACCOMPLISHMENTS 27'