Neutronics Performance Analysis of Cesium Transmutation in Pressurised Water Reactors

Abstract

The rapid development of nuclear reactors has provided us with efficient and clean energy, but at the same time the disposal of spent fuel after fission reaction is facing many problems. In particular, some of the long-lived and highly radioactive fission products (LLFP) in the spent fuel have half-lives of tens of thousands of years or even hundreds of thousands of years, which pose a great threat to the natural environment of human beings. The international community has proposed the ‘separation-transmutation’ method to meet this challenge. This method refers to the extraction of LLFP from fission products, and the treatment of LLFP so that it can be converted into short-lived or low radioactivity nuclides. In this paper, the long-lived fission product Cs-135 was added to a pressurised water reactor fuel assembly for transmutation, and the effect of different Cs loading on the reactivity control of the fuel assembly was investigated. The results show that the introduction of Cs-135 reduces the Keff value of the fuel assembly, and the transient neutron lifetime of the core gradually decreases and the share of slow-generating neutrons increases as the CsF molar ratio becomes larger. In addition, it is found that after the introduction of Cs, the number of thermal neutrons in the fuel assembly decreases because Cs-133 captures and consumes a part of the thermal neutrons to be converted into Cs-135