Deiodination and Solidification of Radioassay Waste

Abstract

We describe our efforts to produce a successful method to purify the liquid 1-125 waste generated from radioassays. The resulting liquid is equivalent to background and can be legally disposed of in public sewage without dilution, after the radioactivity is transferred to a small volume of solid waste. In our procedure liquid waste is acidified with 70% perchloric acid, filtered, then passed through anion exchange columns. With 60 to 90% of the original activity removed, the remainder is soaked on a bed of activated charcoal. After 30 min the remaining activity is below legal limits for disposal for I-125 (88.8 dpm or 4 × 10^-5 μCi/ml). After soaking overnight in charcoal the liquid is equivalent to background levels. This method requires no more time or expertise than a routine radioassay does. In addition, the reagents that we use for this procedure last for about ten weeks, thus reducing our total volume of liquid radioactive waste by almost 12-fold.