中国原子能科学研究院裂变产额研究进展及展望

Research Progress and Prospect of Fission Yield in China Institute of Atomic Energy

  • 摘要: 裂变产额是核能系统与核装置研发的重要数据,同时对裂变物理研究、核天体中元素合成、超重核合成机制等基础研究也具有重要意义。本文主要介绍中国原子能科学研究院在裂变产额研究方面的进展,主要包括采用直接γ能谱法、放射化学法的裂变累积产额实验测量,以及采用动能-速度法的初级裂变产物质量分布实验测量;基于有效核力的裂变微观模型、宏观-微观模型研究;基于机器学习方法、系统学方法的产额数据评价与建库研究。最后对中国原子能科学研究院裂变产额研究的未来发展提出展望。

     

    Abstract: Fission yield is one of the crucial data for nuclear power application and nuclear devices development, and plays an important role in the fundamental research such as nuclear fission physics research, element synthesis in nuclear astrophysics, and the mechanisms of superheavy nucleus synthesis. In this paper, the progress of nuclear fission yield research made by China Institute of Atomic Energy was mainly introduced. First, a series of fission yields measurements were introduced, including: the cumulative yields measurements of important fission systems using direct γ-ray spectrometry, especially the high-precision measurement of fission yields related to burnup; the cumulative yields measurements of low-yield nuclides from 235U fission induced by neutrons, and those of short-lived products from 252Cf spontaneous fission, as well as the mass chain yields and yield-energy relationships of important fission systems using the radiochemical method; measurements of mass distribution of primary fission products from 252Cf spontaneous fission and thermal neutron-induced fission of 235U and 2395Pu based on the kinetic energy-velocity (E-v) method and the established fission fragment identification spectrometer (FFIS). In addition, the innovative work carried out using the microscopic theory of fission was introduced. Within the framework of covariant density functional theory, the two-center harmonic oscillator basis and Fourier parameterization improve the theoretical calculation of the large deformation region close to the scission point, laying a solid foundation for the research on microscopic methods of nuclear fission. Within the framework of the macroscopic-microscopic model, the Langevin method coupled with neutron evaporation model has been developed, in order to consistently describe the fission dynamics and de-excitation process of fission fragments, and the prompt fission quantities including the independent fission yields, and the multiplicities and energy spectra of prompt neutron in 235U fission induced by neutrons are well reproduced using this method. Moreover, the progress of fission yield evaluation and database establishment was introduced, including fission yield evaluation methods based on machine learning, the 5-Gaussian model and the Zp model, as well as the evaluation of experimental data. Finally, the future development and prospects of fission yield research were presented. In terms of experimental measurement, efforts will be made to continuously improve measurement technologies, achieving high-precision measurements of yield-energy relationship data and independent yields. In the research on fission theories, models will be further improved to gradually realize the accurate description of various types of fission data. In addition, experimental data evaluation technologies and fission phenomenological models will be improved, and the evaluation of yields and yield-energy relationships for a series of important fission product nuclei will be completed.

     

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