Deiodination and solidification of radioassay waste

A successful method to purify the liquid I-125 waste generated from radioassays is described. 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 x 10-5 μ Ci/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