Abstract: In one of the final stages of the process at the Mallinckrodt Uranium Refining Center, a 45 per cent nitric acid solution at about 170 F is used to pickle the calcined magnesium fluoride scale off the uranium derbies. The increase in the fluoride-ion content of the bath tends to promote corrosion of the Type 347 stainless tanks. This attack becomes excessive if 0.3 g/liter of fluoride ion or more is present. It was found that if aluminum ion is added to the solution the corrosiveness of the bath can be controlled. Two or three times as much aluminum ion as fluoride ion present is found satisfactory at 170 F. Indications are that the tying up of the fluoride-ion by the complexion [AlF6]8 is responsible for the corrosion control.

Abstract: "Four brazing methods and one other joining process were evaluated for the joining of aluminum spacer fins to flat-plate aluminum-clad fuel elements. None of these methods appear completely suitable for use in a mass-production operation. Furnace brazing and salt-bath brazing were most promising. However, the mechanical problems involved in the application of either process deter their recommendation. Resistance brazing and torch-brazing were proven impractical. The great difference in mass between the two pieces being joined prevents the use of either the resistance or torch method. Pressure bonding is not applicable because of the excessive deformation of parts being joined."