Inhibiting the formation of the compound UAl4 with the minor addition of Si and Zr

As part of the RERTE program (Reduced Enrichment for Research and Test Reactors) various uranium alloys are being analyzed. The program aims to develop a high density uranium-based fuel that remains stable in the body centered cubic (bcc) phase during production and irradiation. The design of the fuel element, currently in use, uses the concept of U-Mo powder dispersed fuel in powdered aluminum forming a compact that is then co-laminated with aluminum in a compact-frame-cap set. However, a widening problem occurs in the dispersion of U-Mo fuel in Al, basically due to the fission gases generated in the Al-fuel interaction zone. The amount and composition of interaction products is a determining factor in the growth and interconnection of the larger sized fission bubbles. The presence of UAl4 among the possible UAlx compounds is not desirable, so its formation should be inhibited in favor of the stabilization of the compound UAl3. One way to solve this problem is by adding alloying agents to the Al matrix as well as to the fuel. Results in the literature show the effectiveness of the alloying agents Si or Zr in amounts that are enough to block the formation of the UAl4 compound. This work proposes a study of the cooperation of both alloying agents to achieve the desired effect. A reference alloy with a weight content of U 49%-Al50,9%-Si 0,1% was smelted in an arc furnace where the presence of the UAl4 compound was verified. Alloys with a growing content of Zr were then smelted while maintaining the contents of the other three elements. Samples of all the alloys were studied by optic and electronic metallography. The identification and crystallographic characterization of the phases are based on spectrum analysis obtained by X-ray diffraction. The presence of the UAl4 phase was detected in the alloys with greater Zr content (6% by weight) (CW)