Radioiodine Speciation in the Hot Cell Effluent Gases of a Radiopharmaceutical Production Facility

Abstract

In order to characterize the various chemical forms of airborne radioiodine species, grab-sampling measurements were conducted at the hot cell laboratory of a radiopharmaceutical production facility, using a selective-adsorbent-iodine filter system. Volatile radioiodine species were produced in the hot cell process which extracted the fission product 99Mo from the irradiated uranium target. The effluent gases were then released through the hot cell filter bank and the main filter bank. Two samplings were made, one at the inlet and one at the outlet of the hot cell filter bank. In comparison with other radioiodine isotopes detected, higher than expected concentrations of 132I were found, primarily in the form of organic iodide--an observation that could be explained by the beta decay of 132Te, the precursor of 132I, in the hot cell waste solution. The relative distribution of airborne 132I was considerably different from that of other iodine radioisotopes. An unexpected component of these distributions was radioiodine penetrating the silver zeolite filter and adsorbed on a triethylenediamine (TEDA) impregnated charcoal filter.