Method for Removing Gadolinium from Used Heavy Water Reactor Moderator

A novel process is described that treats used heavy water moderator (D₂O) contaminated with high concentrations of the neutron poison gadolinium nitrate, Gd(NO₃)₃. Gadolinium is removed by precipitation. The resultant precipitate, GdPO₄6H₂O, represents an extremely rare compound of considerable potential value. The resultant supernatant consisting of residual nitrate, NaNO₃ or KNO₃, is less toxic and easier to process than the original waste. Thus, the alkali metal waste handling can be done with considerably less environmental concern. This waste can potentially be treated by a combination of electrochemical and biological methods.