Methane generated from graphite--tritium interaction. [In hydrogen isotopes separation by cryogenic distillation] [report]

D.O. Coffin, C.R. Walthers
1979 unpublished
When hydrogen isotopes are separated by cryogenic distillation, as little as 1 ppm of methane will eventually plug the still as frost accumulates on the column packings. Elemental carbon exposed to tritium generates methane spontaneously, and yet some dry transfer pumps, otherwise compatible with tritium, convey the gas with graphite rotors. This study was to determine the meihane production rate for graphite in tritium. A pump manufacturer supplied graphite samples that we exposed to tritium
more » ... xposed to tritium gas at 0.8 atm. After 137 day 8 we measured a methane synthesis rate of 6 ng/h per cm 2 of graphite exposed. At this rate methane might grow to a concentration of 0.01 ppm when pure tritium is transferred once through a typical graphite-rotor transfer pump. Such a low methane level will not cause column blockage, even if the cryogenic still is operated continuously for many years.
doi:10.2172/6280302 fatcat:ruele45vw5hclirv3czdye6gui