Separation of Thorium Impurity from Plutonium in the Nitrate Anion Exchange Process.

摘要

Thorium is a common impurity in many materials processed at the Los Alamos Plutonium Facility. Although the thorium impurity level is usually less than 1000 ppM, it frequently exceeds the maximum allowable limit of 100 ppM. Thorium is especially difficult to separate from plutonium because it accompanies plutonium in the three aqueous nitrate processes used at Los Alamos: nitrate anion exchange, oxalate precipitation, and peroxide precipitation. Nitrate anion exchange, the major aqueous plutonium purification process, has recently been modified to remove most of the thorium from sorbed plutonium by washing the column with 4.7 M nitric acid-0.007 M hydrofluoric acid. This chromatographic washing technique requires careful process control that is readily attainable with the recently developed Los Alamos On-Line Gamma Monitor. The successful separation of thorium using this modification has been demonstrated in routine, full-scale, nitrate anion exchange operations. 3 refs., 8 figs. (ERA citation 14:021742)