Abstract: KINETICS STUDY ON THE REDUCTION OF TRACE PLUTONIUM(Ⅳ) BY HYDROXYLAMINE IN NITRIC ACID MEDIAFei Hongcheng Luo Longjun(China Institute of Atomic Energy,P.O.Box 275(26),Beijing 102413)ABSTRACTReaction kinetics of trace Pu(Ⅳ)(c(Pu(Ⅳ))≤10－5 mol/L) with hydroxylamine in nitric acid solution is investigated.The effects of concentrations of Pu(Ⅳ),Pu(Ⅲ),NO－3，H＋ and hydroxylamine on the reduction rate of trace Pu(Ⅳ) are examined.The rate law of reaction of trace Pu(Ⅳ) with hydroxylamine is as follows:－dc(Pu(Ⅳ))dt=k′0c2（Pu(Ⅳ))·c18(NH3OH＋)c2(Pu(Ⅲ))·c3.6(H＋)·(Kd+c(NO－3))2The value of k′0 at 20℃ is (0.0188±0.0028) mol4.8· L-4.8·min－1.The reduction rate of Pu(Ⅳ) increases obviously with increasing temperature and the apparent activation energy with k′0 is equal to 147 kJ/mol.The reaction mechanism of trace Pu(Ⅳ) with hydroxylamine is discussed.Key words Kinetics of reduction Trace Pu(Ⅳ) Hydroxylamine Nitric acid