Reduction of U(VI) in laser liquids POCl3-SnCl4-235UO22+-Nd3+

U (IV) is irreversibly accumulated in the course of the synthesis of POCl3-SnCl4-235UO22+-Nd3+ laser liquids when Nd and U(VI) various source compounds are used independently of the procedure of their introduction. The rate of U(IV) accumulation within POCl3-SnCl4-235UO22+-Nd3+ solutions increases as UO22+ and Nd3+ concentrations increase, in case of the laser liquids with τ>150 mks Nd3+ luminescence die-away time, the observed constant of U(IV) accumulation rate for the second order reaction constitutes k2[U4+]≅(3±1)x10-5 l mole-1 c-1 under T=380 K. U(IV) is accumulated when POCl3-SnCl4-235UO22+-Nd3+ solutions are poured in the airtight glass dishes under the room temperature and under the irradiation of the solutions within UO22+ absorption band by a xenon lamp light. U(IV) is reduced as a result of either chemical or photochemical activation of the uranyl with the formation of U4+ stable complexes with dichlorophosphate-ions and with Nd3+. The excitation deactivation of the uranyl ions by the proton- and chlorine-containing impurities retards U(IV) reduction