Molten salt EMF cell measurements on U–Ga alloys

Abstract

The Gibbs free energies of formation of UGa 3, UGa 2 and U 2Ga 3 were determined by using high temperature molten salt galvanic cell measurements. Three cells were assembled and EMFs were measured. The typical cell is as follows: U( s)// UCl 3 in LiCl– KCl ( eutectic)( l)// U– Ga ( two phase alloy) , where pure uranium is used as one of the electrodes and the other electrode is a two phase U–Ga alloy. The two phase alloys used as the electrodes in the cells I, II and III were 〈UGa 3〉+{Ga},〈UGa 3〉+〈UGa 2〉 and 〈UGa 2〉+〈U 2Ga 3〉, respectively. The Gibbs free energy of formation of UGa 3, UGa 2 and U 2Ga 3 with respect to α-uranium and liquid gallium in the temperature range 644–988, 751–947 and 800–950 K were determined to be −44.1+0.016 T, −46.0+0.017 T and −46.3+0.017T kJ gatom −1 , respectively. The partial molar excess Gibbs free energy of uranium in liquid gallium at 816 K was determined to be −75.5±1.8 kJ gatom −1 and the partial molar enthalpy of uranium in liquid gallium in the saturated solution at 816 K to be −103.2±1.8 kJ gatom −1 .