A pyrochemical process is being developed to recover the longlived alpha-decaying radioactive nuclides from PUREX (plutonium uranium extraction), high-level wastes generated by the reprocessing of spent nuclear fuel. 1 These aqueous wastes contain fission products (noble metals, rare earths, transition metals, rubidium, strontium, cesium, barium, cadmium, tin, selenium) and actinides, the former being predominately short-lived, the latter containing many long-lived radionuclides. Removal of these alpha-decaying actinides from the residues reduces the long-term radiotoxicity and simplifies waste management. 2,3 Molten LiCl-KCl eutectic salt, cadmium and bismuth are used as solvents in the TRUMP-S (transuranic management by pyropartitioning separation) process. Process goals are to remove 99% of the actinides (U, Np, Pu, Am, and Cm) from chlorinated PUREX residues and to recover a product that is greater than 90% actinides by weight. The process separates the waste 4 into four fractions: actinides, rare earths, metals more noble than actinides, and metals more active than the rare earths. Separation of actinides and rare earths as a group from noble and active metals is accomplished by reductive extraction from the chlorinated high-level waste (HLW) residues into liquid Cd. The actinides are separated from the rare earths by electrorefining and countercurrent reductive extraction into liquid bismuth. A full set of consistent thermodynamic property measurements for the actinides and rare earths in the process solvents is required to predict actinide/rare earth separation. Data for the major trivalent actinides were reported previously. 5 Thermodynamic data obtained from measurements for the trivalent rare earths and americium are reported in this paper.Electrochemical potentials were measured and used to calculate the standard Gibbs free energy of formation of the metal chlorides in LiCl-KCl eutectic. Potential measurements at the LiCl-KCl/Cd and LiCl-KCl/Bi interfaces were made to calculate the activity coefficients for Am in the liquid Cd and Bi phases. These thermodynamic properties provide a basis for predicting composition in the salt and metal phases and of the separation products from electrorefining and extraction processes.Equilibrium potential measurements in LiCl-KCl eutectic have been reported previously for the actinides 5 and rare earths. 6 The previously reported rare earth data did not show the same degree of consistency with theory (i.e., calculated ion valence, standard potential temperature dependence) as for the reported actinide results.New data for the rare earths and Am are reported here. Improvements to the electrochemical cell design and experimental procedures were implemented for the experiments reported. For the rare earth chlorides, rare earth metal was deposited onto a Ta cathode to ensure a reliable electrical contact to the rare earth metal in equilibrium with the salt. A thoroughly characterized AgCl-LiCl-KCl salt was used in the reference electrodes. Relatively large amounts of Am a...

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To support the design and operation of the decontamination system using KURION media for the treatment of highly contaminated water accumulated in Fukushima Daiichi Nuclear Power Station, Central Research Institute of Electric Power Industry has urgently carried out many kinds of research and development programs to support the operation of the decontamination system using columns filled with three kinds of KURION media (H, AGH and SMZ). Since the contaminated water at Fukushima Daiichi Nuclear Power Station contained seawater and oil, the effects of sea salt and dissolved oil on Cs adsorption behavior were examined closely by batch type. The concentration of sea salt in the solutions was varied between 0.0 and 3.4 wt%. The Cs adsorption capacity of KURION herschelite in seawater decreased to nearly 1/10th of that in pure water, but it was still concluded that herschelite has sufficient adsorption capacity to remove Cs from the contaminated water. The effect of dissolved oil could be ignored because of its low solubility in seawater. Langmuir-type adsorption isotherm equations, which can be applied for estimating Cs adsorption in sea salt containing water, were developed.

The kinetic characteristics of the column were necessary property to be understood before actual operation. Hence, a functional small-scale zeolite column system was installed for conducting the experiments to understand decontamination behaviors. Each column has a 2 cm inner diameter and a 12 cm height, and 12 g of zeolite-type media was packed into the column. The column experiments were carried out with Kurion-zeolite, herschelite, at different feed rates of simulated water with different concentrations of Cs and sea salt. As expected from equilibrium ion-exchange isotherms obtained for KURION-herschelite, the adsorption of Cs is hampered by the existence of sea salt ratio. The difference in breakthrough behaviors can be ascribed to the difference in sea salt ratio. Above 1000 bed volumes, the adsorption rate of Cs was the same at a solution velocity of between 14 and 81 cm/min. Under the condition of a 3.4 wt% sea salt ratio, the performance of the media supplied by KURION was in the order surfactant modified zeolite < silver-impregnated engineered herschelite = herschelite (H). This result was suggested to evaluate the performance of KURION media on the actual columns.

A pyrometallurgical partitioning technology to recover actinides from high level radioactive wastes is being developed. In the process, actinides are separated from fission products by electrorefining in molten chloride systems. It is expected that REs (rare earth elements), main components of fission products are hardly separated from actinides. In order to estimate separation factors, electrorefining experiments to recover actinides from LiCl-KC1 eutectic salt containing actinide (U, Np, Pu and Am) and RE (Y, La, Ce, Nd and Gd) chlorides were carried out at 45OoC. Actinides were removed from a liquid cadmium anode and recovered as metal on a solid cathode. Typical cathode deposits were rough in appearance and contained 70-90wt% adhering salt. The current efficiency was low because some of the deposit occasionally fell from the cathode. It is shown that uranium, neptunium and plutonium are relatively easily separated from REs and that americium is accompanied by some of REs.

ÃÃElectrometallurgical pyroprocessing is a promising technology to realize actinide fuel cycle. Integrated experiments to demonstrate electrometallurgical pyroprocessing of PuO 2 in continuous operation were carried out. In each test, 10-20 g of PuO 2 was reacted with Li reductant to form metal product. The reduction products were charged in an anode basket of the electrorefiner with LiCl-KCl-UCl 3 electrolyte. Using the anode, deposition of uranium on the solid cathode was carried out when PuCl 3 /UCl 3 concentration ratio was low. After the Pu/U ratio in the salt electrolyte was increased enough, Pu and U were recovered simultaneously on a liquid cadmium cathode. By heating up the deposits for distillation of the salt and the cadmium, U metal or Pu-U alloyed metal was obtained as residues in the crucible. It was the first result to demonstrate the recovery of metal actinides in the continuous operation of pyroprocessing of oxide fuels.