Remnants of ¹³³Xe Radioactivity in a Gas Container

Abstract

From the viewpoint of radiation protection, the remaining amounts of radioactive pharmaceutical ¹³³Xe in a gas container, the influence of aging time of a silicone tube of a gas dispenser on the remaining radioactivity and decrease of radioactivity in a container with elapse time were investigated experimentaly. The formulas to calculate the residual radioactivity in a container were obtained by A (X≤80)=100-1.11×X and A (X>80)=8.44×(0.988), where A and X stand for the percentage of the remnant and the total running time (second) of the gas dispenser respectively. The silicone tubes used several times have little practical influence on the remnant and the residual radioactivity decrease with elapse time as if the half time were 4. 88 days, which was shorter than physical half life of ¹³³Xe, 5.25 days. It was considered the shortening of half time was caused by the leakage of radioactivity from the gas container of about 1 percent a day. From these results, it was concluded that the maximum residual radioactivity in the gas container was 7-12 percents of initial radioactivity in the case of the total running time of 80sec or so and the gas containers as radioactive waste should be disposed after waiting for more than 60 days.