中子诱发锕系元素裂变的宏观-微观理论研究

Study of neutron induced fission of actinides in a macroscopic-microscopic model

宏观-微观模型是核裂变机制理论研究的主要途径之一,是有希望可以很好诠释实验并与实验结果进行定量比较的理论方法.本文综述了在中子诱发锕系元素裂变的宏观-微观理论研究的主要进展.通过开展宏观-微观模型研究,实现了基于五维形变参量的势能曲面的真实计算,利用先进的搜索算法研究获得了核裂变路径、鞍点构型等势能曲面结构信息.基于五维势能曲面上的裂变动力学研究,实现了对主要锕系元素的裂变碎片质量分布数据的理论描述.

The macroscopic-microscopic(MM) model, as a powerful theoretical tool for the understanding of nuclear fission mechanism, is deemed to be a so impressive theoretical method that its calculated results would quantitatively predict the fission observables in the near future. This paper reviews our recent progress in the theoretical calculations of the fivedimensional(5D) potential energy surfaces(PESs) and the fission fragment mass distributions for the neutron induced fission of actinides within the framework of the MM model along with the random walking method and Langevin model.Firstly, we use the 5D generalized Lawrence shape and three quadrature surfaces parameterizations as the shape descriptions, the Lublin-Strasbourg Drop model for the macroscopic energy and the folded-Yukawa model as the singleparticle potential. A new method to use a two-center oscillator basis in calculating Hamiltonian matrix on any kind of shape description is presented. Then, the advanced search algorithms are developed and used in searching for the optimal fission path, fission saddles and other structure information on a 5D PES surface. The method of random walks on 5D PESs is used to calculate the fission fragment mass distributions for the 235U(n,f) reaction. Finally, three-dimensional Langevin model with a constraint on the heavy fragment deformation are applied to study the fragment mass distributions for 14 MeV neutron-introduced fissions of uranium isotopes.