Distribution of Radioactive Elements during Slag Remelting of the Structural Materials of the VVER Fuel Rod Cladding

The PO Mayak radiochemical plant processes spent nuclear fuel (SNF) and generates about 170 t/year metallic radioactive wastes (MRW), which are mainly represented by fragments of the structural materials (SMs) of fuel rod claddings containing residual quantities of radionuclides after fuel dissolution and spent fuel assemblies (SFAs) moved for storage. MRW can be compacted and deactivated by a method based on slag remelting in an induction furnace with a cold crucible. To find the distribution of actinides and fission products (FPs), the slag remelting of the cladding SMs and the SFAs of a VVER-1000 plant is thermodynamically modeled, and the data obtained are experimentally verified. The most probable distribution of actinides and FPs over the melting products is found. The major part of curium and americium is concentrated in a metal, 99 and 94 wt %, respectively. The maximum extraction of uranium in a slag phase in the form of the UO 2 dioxide is 40 wt %. The plutonium distribution over slag (PuO and PuO 1.61 oxides) and metal phases in the temperature range 1500–2000°C is in almost equal proportions. The composition of the gas–aerosol flow represented by FPs is found to consist of 99.78 wt % cesium, 0.05 wt % europium, and 0.17 wt % americium.