Development of an anode structure consisting of graphite tubes and a SiC shroud for the electrowinning process in molten
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Development of an anode structure consisting of graphite tubes and a SiC shroud for the electrowinning process in molten salt Tack-Jin Kim • Gha-Young Kim • Dalseong Yoon Do-Hee Ahn • Seungwoo Paek
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Received: 23 July 2012 / Published online: 17 August 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract In a molten chloride salt-based electrolysis, chloride evolution at an anode needs to be considered in terms of potential fluctuation, capture, and corrosion problems. Here, we demonstrate an anode structure consisting of graphite tubes and a SiC shroud to be applied to the electrowinning process. A large surface area as well as high corrosion resistivity was achieved through the use of inert graphite tubes. The Cl2 (g) capture was enhanced by the employment of a porous SiC shroud. It also allows an efficient contact of the electrode surface to the LiCl–KCl eutectic melt for an anodic evolution. No significant effects of the use of a SiC shroud on the anode overpotential and cell potential were found during the U deposition test. Keywords Electrowinning Anode SiC Graphite tube Cl2 evolution
Introduction Molten salt based pyroprocessing of spent nuclear fuel for actinide recycling received much attention recently [1]. These technologies have been developed by the Argonne National Laboratory (ANL, Argonne West, USA) [2–4]. The Korea Atomic Energy Research Institute (KAERI) began developing pyroprocessing in the mid-1990s. The
T.-J. Kim G.-Y. Kim (&) D. Yoon D.-H. Ahn S. Paek (&) Korea Atomic Energy Research Institute (KAERI), Yuseong-gu, Daejeon 305-701, Republic of Korea e-mail: [email protected] S. Paek e-mail: [email protected]
pyroprocessing developed at KAERI has aimed to reduce the volume of spent fuel accumulated in domestic nuclear power plant facilities and to recycle recovered actinides in sodium-cooled fast reactors (SFR) [5–7]. Pyroprocessing in KAERI consists of three distinct steps (i) the electrolytic reduction to convert the spent oxide fuel into a metallic form (ii) the electrorefining to collect pure uranium (U) onto a solid cathode, and (iii) the electrowinning to recover U and transuranic elements (TRU) simultaneously into a liquid cadmium cathode (LCC). Among them, electrowinning is the main step of pyroprocessing for the simultaneous recovery of U and TRU from fission products, resulting in nuclear non-proliferation. During the co-deposition of U and TRU into a LCC, chlorine evolution is occurred at an anode. The Cl2 (g) occupies and blocks the anode surface area, resulting in the potential fluctuation and a decrease of anode surface area. It may also induce a corrosion problem. Thus, an effective capturing system is required for a stable operation of those actinide recovery processes. Previously, an alumina tube was often used as a shroud to capture Cl2 (g) for anode protection. However, it blocks the movement of chloride ions to the electrode surface, which increases the resistance and induces an anodic overpotential. Therefore, a desired anode structure that allows an
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