Both the Redox and Trigly process had the disadvantage of adding large amounts of nitrate salts to the high-level wastes. The first process free from this disadvantage to be developed was the Butex process, which used dibutyl carbitol (C4 H9 OC2 H4 OC2 H4 OC4 H9) as solvent and nitric acid as salting agent. The nitric acid was evaporated from the aqueous high-level wastes and reused. The Butex process was developed by a group of British chemists [N4] working at the Chalk River Laboratory in the late 1940s. As possible solvents they evaluated diethyl ether, hexone, triglycol dichloride, dibutyl cellosolve (C4H9OC2 H40C4H9), and dibutyl carbitol. They concluded that hexone and dibutyl carbitol were satisfactory solvents, but that dibutyl carbitol was preferable because of its greater stability toward nitric acid and lower vapor pressure.

Following successful pilot-plant tests at Chalk River [N4], the Butex process was adopted for large-scale separation of plutonium, uranium, and fission products from natural uranium irradiated to low bumup at the Windscale plant of the U. K. Atomic Energy Authority [Н8]. Even after its use in this application was replaced by the Purex process, the Butex process remained in use at Windscale for primary decontamination of high-bumup fuel until the 1970s. Then an explosion, probably due to reaction of nitric acid with solvent, terminated its use.