首页|Theoretical perspectives on the reduction of Pu(Ⅳ)and Np(Ⅵ)by methylhydrazine in HNO3 solution:Implications for Np/Pu separation

Theoretical perspectives on the reduction of Pu(Ⅳ)and Np(Ⅵ)by methylhydrazine in HNO3 solution:Implications for Np/Pu separation

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Effective adjustment and control of the oxidation state of plutonium(Pu)and neptunium(Np)is an in-dispensable component of Np/Pu separation in spent nuclear fuel reprocessing.Some hydrazine deriva-tives including methylhydrazine(CH3N2H3)effectively achieves the reduction of Np(Ⅵ)to Np(Ⅴ)without reducing Pu(Ⅳ).Herein,we explored the reduction mechanisms of Pu(Ⅳ)and Np(Ⅵ)by CH3N2H3 in HNO3 solution using scalar-relativistic density functional theory.We elucidated the difference in the re-duction mechanism between Np(Ⅵ)and Pu(Ⅳ)ions by CH3N2H3.The energy barrier for the reduction of[NpⅥO2(H2O)5]2+ and[NpⅥO2(NO3)(H2O)3]+by CH3N2H3 is largely different due to the coordination of nitrate ion.Moreover,the energy barrier of the reduction of[NpⅥO2(H2O)5]2+ is apparently lower than that of[PuⅣ(NO3)2(H2O)7]2+,which is in line with the experimental observations.The results of Mayer bond order and localized molecular orbitals clarify the structural evolution of the reaction path-ways.Analysis of the spin density demonstrates that the first Np(Ⅵ)and Pu(Ⅳ)reduction belongs to the outer-sphere electron transfer and the second Np(Ⅵ)and Pu(Ⅳ)reduction is the hydrogen transfer.This study explains theoretically why CH3N2H3 reduces Np(Ⅵ)but not Pu(Ⅳ),and helps to design promising reductants for the Np/Pu separation in spent nuclear fuel reprocessing.

NeptuniumPlutoniumMethylhydrazineReduction mechanismNp/Pu separation

Xiaobo Li、Qunyan Wu、Congzhi Wang、Jianhui Lan、Meng Zhang、Weiqun Shi

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Fundamental Science on Nuclear Safety and Simulation Technology Laboratory,College of Nuclear Science and Technology,Harbin Engineering University,Harbin 150001,China

Laboratory of Nuclear Energy Chemistry,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China

National Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNational Science Fund for Distinguished Young Scholars

U206721222376197U186720521925603

2024

10.1016/j.cclet.2023.109359

中国化学快报(英文版)
中国化学会

中国化学快报(英文版)

CSTPCD
影响因子：0.771
ISSN：1001-8417
年,卷(期)：2024.35(7)