Reduction of beta activity from depleted derbies, ingots and crucibles

The reduction of beta radiation on uranium ingot and crucible surfaces was demonstrated in the production casting operation by adding a mixture of slag liner material (MgF2) and calcium fluoride to the remelt charge. The beta emitters (234Th and 234Pa) are largely discharged with the fluorides into drums during a remote crucible burnout operation; thereby, reducing operator exposure to beta radiation. A production test showed that very low beta radiation from uranium flat castings can be achieved by using derbies recently prepared by reduction. Plant tests with fluoride addition indicate that pickling of derbies may not be necessary for casting uranium flats from a plasma sprayed (ZrO2) crucible. Also, ingots produced with fluoride additions had less pipe as compared to standard production technique. 2 references, 5 tables