Electrochemical reduction of UO 2 in a LiCl-Li 2 O molten salt using a C anode was investigated. Possible reduction and oxidation reactions were characterized. UO 2 was reduced to U metal but the reduction yield decreased after the repeated use of an electrolyte. CO 3 2− formation and its decomposition to C caused the lowering of current efficiency. The problem of dissolved CO 3 2− should be addressed for the application of C anodes for the metal production in a LiCl-Li 2 O molten salt. Electrochemical reduction of metal oxides is important for the recycling of oxide spent fuels from nuclear power plants as metal fuels for fast reactors.1-3 A LiCl-Li 2 O molten salt due to its high electrolytic conductivity and relatively lower melting point of 606• C has been considered as the most suitable electrolyte for the electrochemical reduction of oxide spent nuclear fuels and UO 2 .Pt anodes have been used in a LiCl-Li 2 O molten salt. 4,5 However, Pt is expensive and unstable due to Li 2 PtO 3 formation and Li attack. Therefore, many efforts have been attempted to develop alternative anodes, but with no successful results. 7 The use of a C anode for the reduction of UO 2 to U in a molten CaCl 2 -CaO was reported.8 However, employing C anodes in a LiCl-Li 2 O molten salt was excluded worrying about the accumulation of C dusts in the salt.We investigated the electrochemical reduction of UO 2 by using a C anode and elucidated the reactions and showed that suppression of CO 3 2− decomposition at a cathode is the key for the success of C as an anode in a LiCl-Li 2 O molten salt. ExperimentalReduction cell.-The electrochemical experiments were carried out in a high purity Ar atmosphere glove box using the same configuration cell shown in Fig. 2 of Ref. 4. A stainless steel crucible was loaded with vacuum dried 700 g of LiCl (99.99%, Aldrich) and 7 g of Li 2 O (99.5%, Cerac) to make a LiCl-1 wt% Li 2 O salt. A Li-Pb alloy (32 mol% Li) of 1 g was placed in a MgO tube with a porous bottom and used as a reference electrode. A graphite rod (Tokai Carbon #G347) centered within a MgO shroud was an anode. The stainless steel cathode basket (9 mm in diameter) was surrounded with a 325 stainless steel mesh (sieve openings of 45 μm) to contain 15 g of crushed UO 2 pellets sieved into a size range of 0.4 mm to 1 mm.Characterization.-Agilent E3633A power supply was used for the voltage control electrolysis. The cathode potential was monitored by a digital multimeter (Agilent, 34405A). Autolab 302N potentiostat was used for the cyclic voltammetry. The working electrode of the cathode scans was a Ni wire (1 mmφ). A Pt wire (1 mmφ) and a graphite rod (8 mmφ) were used as working electrodes for the anodic scans. A Pt plate was employed as the counter electrode. The reduction extent was measured with a thermogravimetry (Seiko TG/DTA 6300). Li 2 O and Li 2 CO 3 concentrations in LiCl were titrated by using 0.1 M HCl and a phenolphthalein indicator with a titrator (Mettler Toledo G20). Results and DiscussionPossible cathode and anode reactions...

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In this study, the hot corrosion behaviour of Inconel 625 weldments in a molten lithium salt (LiCl-1 wt-%Li 2 O) was investigated at 6508C. The hot corrosion behaviour was observed through measurements of the oxide morphology, attack depth and compositional changes of the weldment. The corrosion products of as received (W625) and post-weld heat treated specimens (W625H) under isothermal load were Li 4 MoO 5 and NiFe 2 O 4 , while FeNi 3 , Li 4 MoO 5 and NiFe 2 O 4 were identified as the corrosion products of as received cyclic specimens under cyclic heat load. The difference in weight loss between W625 and W625H was negligible, whereas very low weight loss was observed in cyclic specimens (W625C).