An evaluation of two thin-walled outer tubes showed that more extensive alpha working of the billet core stock results in more uniform cladding on the extruded tube. In an effort to eliminate breakthrough and to reduce eccentricity, shift, and bending of the mandrel, two experimental coppernickel billets with Zircaloy sleeves were extruded to check a modified billet design. lt was observed that the final grain size of the unalloyed uranium core of a thin- walled outer tube is insensitive to small variations in the cooling rate from the beta-treatment temperature. An axia' load of 3000 pounds applied to a thin- walled outer tube during autoclaving was ineffective in preventing bowing of the tube. Shipping experiments demonstrated that current packaging methods of thin- walled inner tubes do not prevent bowing during transit. The fabrication of specimens for the capsule irradiation program was concluded with the shipment of sixteen specimens and excess extruded tube stock to Savannah River Laboratory. The following core compositions were represented: U-1 wt.% Si, unalloyed dingot uranium, U-0.3 wt.% Al-0.5 wt.% Si, and U-0.3 wt.% Cr-0.3 wt.% Mo. All irradiation specimens were supplied in the beta-treated condition. The mechanical behavior of Zircaloy-4-clad dingot uranium tube sections was evaluated …