热管冷却反应堆核热力耦合研究

热管冷却反应堆（简称“热管堆”）高温运行下的结构热膨胀效应会显著影响反应堆的传热和中子物理输运过程。本文提出了一种考虑固体堆芯显著膨胀的几何更新和反应性反馈方法，并构建了基于动态几何的中子物理/热工/力学3场核热力耦合分析程序。在核热力耦合中主要考虑温度引起微观截面的变化、材料密度的变化以及热膨胀引起堆芯尺寸的变化。基于提出的核热力耦合方法，对MegaPower热管堆进行了核热力耦合分析，分析了不同松弛因子下，堆芯功率分布和径向功率因子的收敛性。核热力计算表明，热膨胀造成堆芯边通道的中子泄漏增加，从而产生负反应性反馈；同时，边通道中子泄漏增加加剧了功率分布的不均匀性，传热恶化，考虑核热力耦合后，径向功率因子从非耦合情形的1.20提升到1.23，燃料峰值温度增加11 K。 

Neutronic/Thermal-Mechanical Coupling in Heat Pipe Cooled Reactor

The structural thermal expansion of the heat pipe cooled reactor will significantly affect the heat transfer and neutron physical transport process. A geometric updating strategy and a reactivity feedback method considering the significant expansion of the solid core is presented in this paper, and a neutron physics/thermal/mechanical coupling algorithm based on dynamic geometry is established. In the coupling, the change of the cross section caused by temperature, the change of the density of the materials and the change of the core size caused by thermal expansion are considered. Furthermore, the coupling analyses are applied to the MegaPower heat pipe cooled reactor. The convergence of the core power distribution and the radial power factor under different relaxation factors is analyzed. Results show that the neutron leakage of the side-channel increases due to thermal expansion, which generates negative reactivity feedback and yet aggravates the non-uniformity of the power distribution and the deterioration of the heat transfer. The radial power factor increases from 1.20 to 1.23 when considering the thermal-mechanical feedback. The peak fuel temperature increases by 11 K.