Retention of noble gases by silver zeolite iodine samples

The accident at the Three Mile Island nuclear station resulted in airborne radioactive and iodine concentrations in the plant reactor containment and auxiliary buildings. Measurements of the radioiodine concentrations, normally done by drawing air through charcoal cartridges, were severely complicated by the presence of the radioxenon retained by the charcoal. Hence, it would be desirable to use an alternate iodine absorbing material that does not retain noble gases for such emergencies. Silver zeolite can serve as such a material and was used in many samplings at the Three Mile Island facility to measure radioiodine in the presence of considerably higher concentrations of radioactive zenon. RADeCO charcoal (model CP-100) and silver zeolite (model GY-130) cartridges were used in the measurements. Air was pulled through the two cartridges in series. Exposed cartridges were analyzed with a calibrated Ge(Li) γ-ray spectrometer. The results gave a retention efficiency of charcoal for zenon of 0.03% for 17-min sampling time. This value, then, gives a maximum retention of silver zeolite for xenon in this sample of 2 x 10-6%. (author)