Decontamination of Transuranic Waste Metal by Melt Refining

摘要

Melt refining of transuraniuc- (TRU-) contaminated metals has been proposed as a decontamination process with the potential advantages of reclaiming metal and simplifying analytical problems. The feasibility of routinely achieving the 10 nCi/g (approx. 0.1 ppM) decontamination level by melt refining will demonstrate the removing of scrap metal from the TRU waste classification. To demonstrate this feasibility, mild steel, stainless steel, nickel, and copper were contaminated with 500 ppM PuO sub 2 and melted with various fluxes. Four different fluxes, borosilicate glass, blast furnace slag, high silica slag, and artificial basalt, were used in these studies. The solidified slags and metals were analyzed for their plutonium contents by the use of a combination of wet chemical and alpha -activity counting technique. Partition ratios were calculated for plutonium using the analytical results of each experiment. Some metals were doubled refined to study the effect of secondary slag treatment. The initial weight of the slags was also varied to investigate its effect on plutonium removal. The results indicated that the use of proper slags is necessary for effective removal of plutonium. All four slags were effective in removing plutonium from the metals. Values of less than 1 ppM Pu (approx. 100 nCi/g) could be obtained in all cases. The double-refined samples were cleaned to less than 0.1 ppM Pu (approx. nCi/g), which is the goal. Variation in the slag weight did not change the results significantly. Double refining of the metal with small primary and secondary slag volume can be an effective process for removal of TRU contaminants from metals.