Technology and Equipment Based on Induction Melters with.Cold. Crucible for Reprocessing Active Metal Waste
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Technology and Equipment Based on Induction Melters with “Cold” Crucible for Reprocessing Active Metal Waste V.G. Pastushkov, A.V. Molchanov, V.P. Serebryakov, T.V. Smelova, I.N. Shestoperov SSC RF VNIINM, Rogov st. 5, 123060, Moscow, Russia ABSTRACT The operation and, particularly, the decommissioning of NPPs and radiochemical plants result in substantial arisings of radioactive metal waste (RAMW) having different activity levels (from 5×10-4 to ≈ 40 Ci/kg). This paper reviews the specific features of the technology and equipment used to melt RAMW in electric arc and induction furnaces with ceramic or “cold” crucibles. The experimentally determined and calculated data are given on the level to which RAMW is decontaminated from the main radionuclides as well as on the distribution of the latter in the products of melting (ingot, slag, gaseous phase). Special attention is focused on the process and the facility for the induction-slag melting of RAMW in furnaces equipped with “cold” crucibles. The work described is under way at SSC RF VNIINM to master the technology of melting simulated high activity level Zr-alloy and stainless steel waste. INTRODUCTION All the countries that adhere to the closed fuel cycle in the nuclear power developments are engaged in processing spent nuclear fuel and treating resultant radioactive waste (RAW). The decommissioning of 1 NPP unit of 1000 MW electric power results in 15 to 42 thousand tons of RAMW. Some 1.5% of the total mass of steels used in a reactor have ≈40 Ci/kg and contain 99.8% of the total activity. The reprocessing of LWR spent nuclear fuel at a radiochemical plant of 600 t U/year will result in ∼ 190 t of high activity level metal waste of which chopped fuel rod claddings and end pieces of fuel assemblies constitute ∼ 170 t and ∼ 20 t, respectively, with the overall volume of ∼ 200 m3. The waste contains long-lived radionuclides (Cs, Sr, Ru, Pu) basically at the surface layers of the claddings and activation products (Fe, Co, Ni) in the FA end pieces [1]. Currently the waste is stored in special storage facilities. The long-term storage of RAMW in specially designed storage facilities is cost ineffective (the cost of 1 m3 low activity level metal waste storage is more than 600 $ US/year at the prices of 1998). Those expenses can be reduced by RAMW decontamination and melting.
The melting of RAMW can have several favorable aspects: • • • •
a factor of 4-6 reduction of waste and, correspondingly, of storage and burial facility volumes; conversion of some RAMW to intermediate- and low-level waste with the resultant simplification and lower cost of storage; simplified measurement of specific and total activity of RAMW (particularly, for large sizes and volumes of waste when only random control is feasible); the possible radioactive contamination of the environment is almost fully eliminated due to the uniform distribution and reliable immobilization of radionuclides in the metal matrix [2].
EXPERIMENTAL To melt radioactive steel electric arc and induction facilities were
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