In pyroprocessing, the residual salts (LiCl containing Li and Li2O) in the metallic fuel produced by the oxide reduction (OR) process are removed by salt distillation and fed into electrorefining. This study undertook an investigation into the potential viability of employing a separate LiCl salt rinsing process as an innovative alternative to conventional salt distillation techniques. The primary objective of this novel approach was to mitigate the presence of Li and Li2O within the residual OR salt of metallic fuel, subsequently facilitating its suitability for electrorefining processes. The process of rinsing the metallic fuel involved immersing it in a LiCl salt environment at a temperature of 650°C. During this immersion process, the residual OR salt contained within the fuel underwent dissolution, thereby reducing the concentrations of Li2O and Li generated during the OR process. Furthermore, the Li and Li2O dissolved within the LiCl salt were effectively consumed through chemical reactions with ZrO2 particles present within the salt. Importantly, even after the metallic fuel had been subjected to rinsing in a conventional LiCl salt solution, the concentration of Li and Li2O within the salt remained consistent with its initial levels, due to the utilization of ZrO2. Moreover, it was observed that the Li- Li2O content within the metallic fuel was significantly diluted as a result of the rinsing process.

The mixing powder of vitrification material and metallic oxide sludge was solidified by hot isostatic press method and was tested to check whether the solidified waste disposal acceptance criteria were met or not. From various contaminated tank in nuclear power plants, and other nuclear energy facilities, radioactive sludge based on metallic oxide can be generated. The most of tank consist of stainless steel can be oxidated by the long-term exposure on oxygen and moisture, and then can be made sludge layer based on metallic oxide on the inner wall of contaminated tank. Radioactive sludge waste should be solidified and disposed. Melting and hardening is the most basic method for solidification. The melting points of metallic oxide of stainless steel as Fe3O4, NiO, Cr2O3 are 1597, 1955, 2435, respectively. Those are very high temperature. To melt these metallic oxides, a furnace capable of raising the temperature to a very high temperature is required, which requires a lot of thermal energy, which may lead to an increase in disposal cost. Therefore, it is necessary to lower the melting point and solidify non-melted metallic oxide powder by adding vitrifying material powder as Na2O, SiO2, B2O3. The more vitrification material is added, the easier it is to solidify the sludge based on metallic powder at a low temperature, but there is a problem in that the total waste volume increases due to the addition of vitrification material. In this study, the mixing ratio and temperature conditions that can fix the sludge while adding a minimum amount of vitrification material will be confirmed. Mixing ratio conditions of the vitrification material and sludge powder are 10:90, 15:85, 20:80, 25:75. To fix the metallic oxide sludge by melting only the vitrification material without completely melting the metallic oxide, compression by external pressure is required. Therefore, the HIP (Hot Isostatic Pressing) method was used to solidify the metallic oxide sludge by simultaneously heating and pressurizing it. Because the softening points of most of vitrification based on Na2O, SiO2, B2O3 are ranged from 800 to 1000, temperature conditions are 800, 900, 1000. Since the compressive strength for disposing of the solidified materials was 3.4 MPa, the maximum pressure condition was set to 5000 psi (about 34 MPa), which is 10 times 3.4 MPa. And optimal mixing ratio, temperature, pressure conditions that meet the solidified waste disposal acceptance criteria will be found.

Metallic tantalum powder is manufactured by reducing tantalum oxide (Ta2O5) with magnesium gas at 1,073–1,223 K in a reactor under argon gas. The high thermodynamic stability of magnesium oxide makes the reduction reaction from tantalum oxide into tantalum powder possible. The microstructure after the reduction reaction has the form of a mixture of tantalum and magnesium oxide, and the latter could be entirely eliminated by dissolving in weak hydrochloric acid. The powder size in SEM microstructure for the tantalum powder increases after acid leaching in the range of 50–300 nm, and its internal crystallite sizes are observed to be 11.5 to 24.7 nm with increasing reduction temperatures. Moreover, the optimized reduction temperature is found to be 1,173 K as the minimum oxygen concentration is approximately 1.3 wt.%.

For this paper, we investigated the area specific resistance (ASR) of commercially available ferritic stainless steels with different chemical compositions for use as solid oxide fuel cells (SOFC) interconnect. After 430h of oxidation, the STS446M alloy demonstrated excellent oxidation resistance and low ASR, of approximately 40 mΩcm2, of the thermally grown oxide scale, compared to those of other stainless steels. The reason for the low ASR is that the contact resistance between the Pt paste and the oxide scale is reduced due to the plate-like shape of the Cr2O3(s). However, the acceptable ASR level is considered to be below 100 mΩcm2 after 40,000 h of use. To further improve the electrical conductivity of the thermally grown oxide on stainless steels, the Co layer was deposited on the stainless steel by means of an electroless deposition method; it was then thermally oxidized to obtain the Co3O4 layer, which is a highly conductive layer. With the increase of the Co coating thickness, the ASR value decreased. For Co deposited STS444 with 2 μmhickness, the measured ASR at 800˚ after 300 h oxidation is around 10 mΩcm2, which is lower than that of the STS446M, which alloy has a lower ASR value than that of the non-coated STS. The reason for this improved high temperature conductivity seems to be that the Mn is efficiently diffused into the coating layer, which diffusion formed the highly conductive (Mn,Co)3O4 spinel phases and the thickness of the Cr2O3(S), which is the rate controlling layer of the electrical conductivity in the SOFC environment and is very thin