Abstract: The invention provides a method of operating a cascade gas separation process and a gas separation cascade (10) useful for uranium refining and employing a carrier gas. The method and cascade of the invention involve arranging relative gas flow rates between at least some modules (12) in the cascade so that the relative proportions of process gas leaving and entering each of said modules are such that there is a substantially constant molar flow rate of gas in each direction along the cascade through said modules. The proportion of carrier gas relative to process gas increased in opposite directions from the feed (14) to the opposite ends (20, 22) of the cascade and the modules through which the constant molar flow rate takes place have substantially the same size, capacity and construction.

Abstract: A method of conducting an aluminothermic reduction of an oxide of a reactive metal comprising melting in a vessel in an induction furnace a conductive susceptor metal and thereafter adding the required intimately mixed reactants to the molten mass in the container wherein the rate of addition of the reactants and the power input to the induction furnace are controlled to maintain the temperature of the molten mass above a predetermined minimum.

Abstract: Treating fluid of a single phase by feeding a stream of it into a passage so that its composition varies in a known fashion regarding a specific property over a cross-section of the stream transverse to its direction of flow. The stream is moved along the passage and parts of the stream having different compositions are separated before the variation disappears.Fluid treatment apparatus defines a passage forming at least part of a circuit. The circuit has an inlet and an outlet and means for causing flow of a single phase fluid around the circuit, and for circulating at least part of the fluid more than once around the circuit, along a helix-like path.