Engineering of Fuel Plates on Uranium-Molybdenum Monolithic: Critical Issues
Engineering of nuclear fuels using monolithic plates of uranium-molybdenum and Al-6061 cladding is the current challenge for research and test reactors. The main drawback of the manufacture of monolithic nuclear fuel was analyzed using two surface coating methods: aluminum sputtering and transient liquid phase bonding (TLPB). Coating was done with a commercial alloy of Al-Si (R-4047). These techniques were used to improve the metallurgical bonding between the UMo and the cladding by rolling. Finally, design parameters and manufacture of UMo plate fuels were established. Mechanical tests were used to characterize the plates, resulting in UTS values of about 700 and 1000 MPa for the UMo alloys. These results are complemented with metrological analyses, X-Ray diffraction (XRD), thermal analyses, and metallography. X-rays and ultrasound scanners were used to monitor bonding and the co-rolling effects. These initial results show the main obstacles to the engineering development of UMo monolithic plate fuels with Al-6061 cladding, and these are discussed herein.
UPDATE ON MONOLITHIC FUEL FABRICATION METHODS
Efforts to develop a viable monolithic research reactor fuel plate have continued at Idaho National Laboratory. These efforts have concentrated on both fabrication process refinement and scale-up to produce full sized fuel plates. Progress at INL has led to fabrication of hot isostatic pressed uranium-molybdenum bearing monolithic fuel plates. These miniplates are part of the RERTR-8 miniplate irradiation test. Further progress has also been made on friction stir weld processing which has been used to fabricate full size fuel plates which will be irradiated in the ATR and OSIRIS reactors.
LAYER GROWTH DURING INTERDIFFUSION IN THE ALUMINUM-URANIUM ALLOY SYSTEM
Interdiffusion in the aluminum-uranium system was investigated over the temperature range 400 to 600 deg C and the pressure range 1 1/4 to 10 tsi for diffusion times of 24 hr and less. The pressure-induced increase in UAl/sub 3/ layer thickness has been confirmed. Interesting correlations are shown to exist between annealing time, annealing temperature, and applied pressure on the one hand, and the nsture and distribution of structural defects in the UAl/sub 3/ diffusion zone on the other. It is demonstrated that the solubility range within the UAl/sub 3/ phase must be at least 2.6 at.% uranium. It is shown that the growth of the UAl/sub 4/ and UAl/sub 2/ phases in incremental couples is much slower than the growth of UAl/sub 3/ in aluminum -uranium couples. Finally, it is proposed that the effect of pressure on UAl/sub 3/ layer growth is primarily mechanical in that higher pressures repress the tendency for the formation of macroscopic voids and thus effectively increase the cross-sectional area available for interdiffusion. (auth)