PROCESSING HIGH-LEVEL LIQUID WASTE BY SUPER-HIGH-TEMPERATURE METHOD .4. REDUCING REACTIONS AND ALLOY FORMATION BY PLATINUM-GROUP ELEMENTS, MOLYBDENUM AND CORROSION PRODUCTS TAKING PLACE IN SIMULATED HLLW

An experimental study made on the reducing reactions and the formation of alloys taking place in oxide mixtures representing high-level liqu id waste (HLLW) generated by the PUREX process, and in particular, on the effect brought on the metal melting temperature by the presence of corrosion products mainly Fe, Cr, Ni deriving from the vessels used i n the process. It proved that heat treatment at 1,873 K melted the met al phases produced from all the starting mixtures taken up. The metal phases obtained from starting mixtures of corrosion products or their oxides proved to contain alloys of Cr-Fe-Ni, Fe-Ni and Cr-Ni, and in a ddition Ru-Fe alloy and Mo, Pd metals when the starting mixture furthe r included platinum metals and molybdenum oxides, which also are found in the HLLW from PUREX process. The same six alloys and metals cited above were formed in the metal phases obtained from simulated calcined HLLW used as starting mixture. The melting of Ru and Mo at 1,873 K fa r below their melting points was attributed to the dissolution of Fe i nto Ru and of Fe or Ni into Mo.