METALLURGY DIVISION QUARTERLY PROGRESS REPORT FOR PERIOD ENDING OCTOBER 31, 1951

Abstract

Eleven thorium-carbon alloys in the range 0.02 to 2.0% carbon were prepared by vacuum-arc melting. The hardness varied from 19 R/sub A/ for the 0.02% alloy to 108 R/sub B/ for the 2.0% alloy. The preparation of thorium- chromium alloy was hampered by a reaction with the zirconia molds, which results in porosity in the casting. The failure of aluminum-silicon bonded X-10 slugs after heat treatment for seven days at 400 deg C was traced to the failure to remove tin after the tin dip and the presence of a gas during heat treatment. Tensile tests were made on extruded thorium, and no correlation was found with extrusion variables. A composition effect was found, however, which showed a linear relationship between carbon content and tensile strength. Creep tests on thorium, uranium, and Inconel continue. The program of evaluating the variables in the fabrication of clad fuel elements, using MTR techniques was concerned mainly with the distribution of UO/sub 2/ in the core compact, the temperature of rolling, and the particle size of the metallic core powder. Progress is being made in the preparation of three-layer laminates without the use of a protective can during the hot-rolling operation but with the use of a hydrogen atmosphere during the preparatory heating. Molten hydroxides of barium, sodium, strontium, lithium, and potassium and molten sodium cyanide were used in corrosion tests at 1500 deg F. Nickel, copper, and Monel appear to be the only commercially available materials that resist chemical reaction with the molten hydroxides and sodium cyanide at this temperature. Mass transfer, however, presents a difficult problem. Stainless steels coated with copper and nickel are a logical development and heavier coatings show promise. Nitrogen and carbon diffusion into metal appears as a primary difficulty in containing sodium cyanide at 1500 deg F in a number of commercial alloys. Nickel and iron, however, give no evidence of interaction. The stainless steels vary in their tendency to interact. Mass transfer in thermal convection loops continues to cause early termination of runs in which the liquid media is a hydroxide. In tests,tubes under helium pressure are immersed into a bath of the desired liquid and left for 1000 hr or until failure. Type-316 stainless steel and Inconel were tested. Early failure of the Inconel is believed to be due to faulty tubing, since tubing from a new batch has been under test for some time without signs of failure. The diffraction of neutrons by liquid metals was attempted to gain information on the structure of liquids. Both lead and bismuth were run in a specially designed furnace that fits the neutron spectrometer. A mathematical analysis of the data is under way. The basic studies on the interactions of solid and liquid metals continue. By careful control of temperature gradients and of thermal cycling, mass transfer in copper-bismuth systems could be made either negligible or appreciable. The largest temperature deviation that can be tolerated in thermal cycling of a static system is 2 deg C. A basic study was started to determine the effect of oxygen on the corrosion of metals by sodium hydroxide. Thermal convection loops are being run to de- termine the effect of oxygen on a dynamic sodium hydroxide-nickel system. The first loop was stopped after over 300 hr of operation. Appreciable mass transfer occurred in this loop, which had been loaded in a helium atmosphere and sealed off under vacuum. The feasibility of cone-arc welding of tube-to-header joints was demonstrated. Spot welding was shown to be a good method for joining tube-bundle straps to fuel tubes. (For preceding period see ORNL-1108.) (auth)