Mass Distribution of the Fission Products of Plutonium Isotopes as Calculated by Using a Semi-empirical Model
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Mass Distribution of the Fission Products of Plutonium Isotopes as Calculated by Using a Semi-empirical Model Jounghwa Lee Department of Physics, Sungkyunkwan University, Suwon 16419, Korea and Nuclear Physics Application Research Division, Korea Atomic Energy Research Institute, Daejeon 34057, Korea
Young-Ouk Lee Nuclear Physics Application Research Division, Korea Atomic Energy Research Institute, Daejeon 34057, Korea
Tae-Sun Park Center for Exotic Nuclei Studies, Institute for Basic Science, Daejeon 34126, Korea and Department of Physics, Sungkyunkwan University, Suwon 16419, Korea
Seung-Woo Hong∗ Department of Physics, Sungkyunkwan University, Suwon 16419, Korea (Received 2 June 2020; revised 15 July 2020; accepted 3 August 2020) The fission product yields (FPYs) of plutonium isotopes induced by thermal, 500-keV and 2-MeV neutrons are calculated by using a semi-empirical model recently developed and applied to uranium isotopes. In this model, the FPYs are assumed to be proportional to the level density of a compound nucleus at the fission barrier. The fission barrier height that determines the level density is modeled as a sum of a macroscopic term and four microscopic terms. The model has ten parameters, four of which are taken to be the same as those fixed for the uranium isotopes. The remaining six parameters are adjusted to reproduce the FPYs of plutonium isotopes. The resulting parameters for the plutonium isotopes are discussed in comparison with those for the uranium isotopes. The calculated FPYs are compared with experimental and evaluated data, as well as the calculation results from other fission models such as GEF and TALYS. Our semi-empirical model is shown to reproduce the overall features of the FPYs of plutonium isotopes. Keywords: Nuclear fission, Fission product yields, Semi-empirical method, Plutonium DOI: 10.3938/jkps.77.1082
I. INTRODUCTION Fission product yield (FPY) data are of vital importance for various applications such as design and operation of reactors, calculation of decay heat, and handling of spent nuclear fuels. Accurate FPY data are essential not only for the applications but also for the fundamental understanding of fission processes [1–3] and the study of the production of r-process elements in explosive nucleosynthesis or neutron star merger ejecta [4,5]. Therefore, the FPY has been intensively investigated both experimentally [6–18] and theoretically [19–27]. Though accurate calculations of the FPY by using a fully microscopic model are in progress, computing resources are demanding in such microscopic methods [3]. On the other hand, semi-empirical models [28,29] can be useful in describing ∗ E-mail:
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pISSN:0374-4884/eISSN:1976-8524
fission product yields (FPYs) in a simple manner and yet with a relatively good accuracy. A semi-empirical model recently developed [30] for the description of the FPY was able to reproduce the overall features of the FPYs of uranium isotopes with a relatively good accuracy. In the present work, we apply the model to plutonium isot
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