铅冷行波堆反应性变化规律及其影响因素研究

铅冷行波堆具有安全性好、倒换料周期长、铀资源利用率高等突出优势，是先进核能系统的重点发展方向之一，实现反应性微小变化是铅冷行波堆堆芯方案设计的关键技术问题。本文以热功率700 MW、采用金属燃料的铅冷行波堆物理方案为研究对象，重点研究了堆芯点火区及增殖区设计参数变化对有效增殖因子（k_eff）的影响，分析了全寿期堆芯反应性的变化趋势。数值结果表明:点火区设计参数显著影响堆芯初始k_eff，点火区的易裂变核素装量越大，初始k_eff越大，通过调整点火区在堆芯轴向位置及其燃料富集度可有效降低反应性变化幅度；堆芯装载的可转换核素与易裂变核素之比越高，增殖产生的239Pu越多，整体增殖性能越好；增殖区越长，平衡态持续时间越长，堆芯寿期越长。本文研究结论可为铅冷行波堆堆芯物理方案设计及关键参数选择提供重要理论依据。 

Study on Reactivity Variation and Its Influencing Factors of Lead-cooled Traveling Wave Reactor

Lead-cooled traveling wave reactor has outstanding advantages of good safety, long refueling and shuffling cycles, and high utilization rate of uranium resources. It is one of the key development directions of advanced nuclear energy system. Realizing the small change of reactivity is the key technical problem in the core scheme design of lead-cooled traveling wave reactor. Taking the physical scheme of lead-cooled traveling wave reactor with thermal power of 700MW and metal fuel as the research object, this paper focuses on the influence of the design parameters of core ignition zone and breeder zone on the effective multiplication factor (k_eff), and analyzes the change trend of core reactivity in the whole life. The numerical results show that ignition zone design parameters significantly affect the initial k_eff of the core. The larger the amount of fissile nuclides in the ignition zone, the larger the initial k_eff. The variation range of reactivity can be effectively reduced by adjusting the axial position of the ignition zone in the core and its fuel enrichment; The higher the ratio of convertible nuclides to fissile nuclides loaded in the core, the more 239Pu produced by breeding, and the better the overall breeding performance; The longer the breeder zone, the longer the duration of equilibrium state and the longer the core life. The conclusions of this paper can provide an important theoretical basis for the physical scheme design of lead-cooled traveling wave reactor core and the selection of key parameters.