PERFORMANCE OF U-PU-ZR FUEL CAST INTO ZIRCONIUM MOLDS

To investigate a means of eliminating quartz mold waste, U-3Zr and U-2 0.5Pu-3Zr fuel was injection cast into Zr tubes, or sheaths, and clad in 316SS. These elements and U-10Zr and U-19Pu-10Zr fuel elements, cas t in the standard manner into disposable quartz molds, were irradiated in EBR-II to 2 at% burnup and removed for interim examination. Measur ments of fuel column axial growth indicate that the Zr-sheathed fuel e xhibited significantly less axial elongation than the standard-cast fu el (1.3 to 1.8% versus 4.9 to 8.1%). Fuel material extruded through th e ends of the Zr sheaths, contacting the cladding in some cases. Trans verse metallographic sections reveal cracks in the Zr sheath, indicati ng that the sheath is not a sufficient barrier between fuel and claddi ng to reduce fuel-cladding chemical interaction (FCCI). FCCI effects w ill be monitored as the elements attain higher burnup.