PB-FHR的控制棒布局设计及物理效应

Layout design and physical effect analysis of control rod in PB-FHR

反应性控制系统的设计是反应堆物理设计的主要内容之一。氟盐冷却高温球床堆(Pebble Bed-Fluoride salt-cooled High temperature Reactor,PB-FHR)用B4C吸收体的控制棒作为反应性控制的主要手段。所有控制棒分布于石墨反射层的孔道中,其空间布局、几何结构、中子吸收体的特性参数等是影响控制棒反应性控制的关键因素。本文基于SCALE6程序,以10 MW固态燃料钍基熔盐堆(Thorium Molten Salt Reactor-Solid Fuel,TMSR-SF1)(属于PB-FHR)设计模型为参考,系统研究了石墨反射层中控制棒径向位置、有效行程、棒体结构、吸收体长度、吸收体密度等因素对控制棒价值的影响。结果表明,控制棒的径向位置对控制棒价值影响较大;控制棒吸收体长度需综合考虑上下限位及极限下插限位对价值变化的影响;^(10)B的原子密度变化对控制棒价值影响较小。本研究为PB-FHR的反应性控制系统的设计及控制棒的制造加工提供理论参考。

[Background] Reactivity control design is a key part of reactor neutronics design. The control-rods made of BaC-absorber for reactivity control in pebble bed-fluoride-salt-cooled high-temperature reactor （PB-FHR） are located in the hole of side graphite. The space layout, geometric structure, absorber properties are the key influencing factors to the reactivity control. [Purpose] This study aims at the influence of different factors of the control rod in graphite reflection layer on control rod worth, including radial position, effective stroke, absorber length, absorber density, etc. [Methods] The 10-MW thorium molten salt reactor-solid fuel （TMSR-SF1） model was taken as the reference reactor, and the calculation was completed based on SCALE6. All above mentioned factors such as radial position, effective stroke, absorber length and absorber density, were taken into account for parameters design. [Results] Computational results reveal that radial position of the control rod has obvious impact on control rod worth. The absorber length, the upper limit, lower limit and overflow lower limit of the control rod that lead to the change in worth, should be considered comprehensively. The influence of 10B atomic density on control rod worth was negligible. [Conclusion] This study provides basic theoretical reference for the design of PB-FHR reactivity control.