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Description
Part of the accumulated metallic radioactive waste is superficially contaminated. The surface activity may be minor contamination resulting from the deposition of radionuclides during equipment operation [1]. This means that accumulated metallic radioactive waste can be purified of radioactive contamination after processing and, consequently, reused in the industry.
In this regard, Experiments were conducted to study the possibility of using the electroslag remelting (ESR) method to purify radioactively contaminated metal. The facility is an electroslag furnace with a water-cooled crystallizer of a closed type. The crystallizer provides melting of the electrode metal and the working flux at a temperature of ~ 2000 °С and forms and ingot [2]. Figure 1 shows the scheme of ESR facility.
In the experiments, steel pipes were selected as a radioactively contaminated metal, from which molten electrodes were made. Steel pipes were used to test fuel elements and fuel assemblies of nuclear thermal rocket before upgrading the cooling system of the IVG.1 reactor [3].
In total, two experiments were conducted on remelting steel pipes. Table 1 shows the results of radionuclide activity measurements in the electrode before the start of the experiments and in samples taken from the electrodes after remelting.
As we can see, the steel pipes could be classified as low-radioactive waste in the initial state. Gamma-ray spectrometric measurements have shown that radionuclides Co-60, Cs-137 and U-235 contribute to the main activity of MRW. The activity of the metal decreases due to its purification from radioactive purification after remelting. The use of ESR is characterized by high efficiency in cleaning the steel pipes from uranium and caesium.
Uranium was not detected in the studied samples. Most likely, its concentration in the samples was lower than the minimum detectable value in the used gamma-ray spectrometer. At the same time, the activity of the Co-60 remains almost at the initial level and is due to the choice of flux for ESR.
Thus, the application of electroslag remelting to steel pipes resulted in a significant reduction in the total radioactivity of the metallic radioactive waste. The obtained results confirm the fundamental feasibility of effectively decontaminating MRW using this method.
