Tsuguyuki Kobayashi

Electrorefining Experiments to Recover Uranium with a Cadmium-Lithium Anode and Their Theoretical Evaluation

Molten salt electrorefining experiments were performed using a liquid metal anode made of cadmium-lithium alloy to recover uranium to a solid cathode from the spent molten salt. The concentration of U3+ in the molten salt effectively decreased from 1.38 wt% to less than 0.01 wt%. However, it was revealed that about 10 to 40% of uranium was not recovered by the solid cathode. This U deficit was thought to be caused by the U reduction around the Cd-Li anode. The following two mechanisms were proposed: 1) electrochemical deposition of uranium and 2) dissolution of the atomic lithium (Li0) into the LiCl-KCl eutectic salt and concomitant reduction of U3+ by the Li0. A computer code PALEO was developed to interpret these results more quantitatively. It was found that the PALEO code was able to simulate the evolution of U3+ concentration in the salt as well as the electrodes potential reasonably well and the mechanisms of 1) and 2) could explain the dependency of U deficit if the diffusion coefficient of Li0 in ...

Low Current Efficiency in MOX Deposition Tests

A series of MOX deposition tests has been performed since 2001 at RIAR to clarify its complex phenomena and to improve its poor current efficiency. In the 2001 tests, the cathode current efficiency was between 60 and 100% but the Pu fraction in the MOX was between 5 and 20%. In 2002 tests, the fraction was raised to more than 30% by modifying the test conditions but the current efficiency fell to between 20 and 60%. A new method was proposed to simulate the parasitic current due to the electrode reactions of UO2 2+/UO2+, Pu4+/Pu3+ and Fe3+/Fe2+ at the cathode. It was found that the parasitic current due to the UO2 2+/UO2+ reaction significantly lowers the current efficiency especially when the cathode potential is kept near the equilibrium value during the electrolysis to increase the Pu fraction in the MOX deposit.

Calculation of Gamma-Ray Production Cross Sections at Neutron Energies of 1–20 MeV

In order to prepare the p-ray data library requested in a design of fission and fusion reactors, γ-ray production cross sections and spectra of Al, Si, Ca, Fe, Ni, Cu, Nb, Ta, Au and Pb have been obtained at the neutron energies of 1–20 MeV, using a spin-dependent multi-step evaporation model. Calculations include dipole and quadrupole transition without the distinction between electric and magnetic process, and take explicit account of the role of yrast levels. The effects of the yrast levels and γ-ray strength function upon γ-ray production are also investigated in relation to particle emission. At the incident neutron energies where (n,nγ ) and/or (n,2nγ ) reactions are dominant, the present model is shown to be able to predict the production of secondary γ-rays (<9.0 MeV) from medium-heavy to heavy nuclei with reasonable accuracy.