Preparation of tritium standard gas by the use of tritiated methane.

Tritium standard gas for calibrating radioactivity detectors was prepared by the use of tritiated methane synthesized by the reaction of tritiated water with aluminum carbide at ca. 470 degrees C. A long-path proportional counter was used to standardize the radioactivity of the prepared gas. Tritiated gas of less than 10(4) Bq could be measured by this counter with the overall error of 3.5% (3 sigma). Finally, two types of standard were prepared in a metal cylinder and a glass ampoule. The latter type could be used as a handy calibration source for detectors.