Alloying of Pu-Al with Stainless Steel for Material Disposition

The Savannah River National Laboratory has evaluated several options for the disposition of stainless steel (SS)–clad plutonium metal alloy. One of the technologies under consideration is alloying of the material with SS. The resulting SS-Pu alloy would be a nonproliferable waste form consisting of a secondary Pu composition region microencapsulated in the refractory SS. Two 8-kg ingots were made at SS-1.8Zr-0.4Pu alloys (in weight percent); 8 kg was determined in a previous study to be the maximum mass of SS ingot at the maximum target Pu loading of 350 g that would result in a SS-4.4Pu alloy (in weight percent). Two smaller 500-g ingots were also produced at SS-1.6Zr-1.4Pu and SS-1.4Pu (in weight percent). The alloying of 500-g ingots at a higher Pu concentration than in the 8-kg ingots was evaluated, and the necessity of adding Zr metal to incorporate the Pu and control Pu oxidation was evaluated. Zirconium addition was found to be unnecessary to incorporate the Pu and control Pu oxidation. Drill turnings were collected from the large and small ingots, and metallographic samples were directly cut from the small ingots. Both were analyzed to validate the structure and composition region formation. Chemical analyses of turnings proved that the Pu was dispersed within the SS ingots.