球床式高温气冷堆球流混流影响的机理

Mixing flow mechanism in the pebble bed high temperature gas cooled reactor

球床高温气冷堆球流运动存在由于随机扰动引起的混流现象,它对于功率分布等堆芯关键参数有影响。通过开发工具、定量分析,发现其影响较小,而多次通过的燃料循环方式有效降低堆芯关键参数由于燃料球随机运动而造成的计算不确定性。球流混流使得堆芯不同区域内不同价值的核燃料球实现交混,对比分析堆芯各区域核密度及燃料球燃耗深度变化结果表明:混流效应使堆芯各区域核密度发生变化,但球床式高温气冷堆堆芯燃料球分布和运动使得堆芯各区域核密度差异不大,而多次通过使此差异更小;因此混流效应使得各区域核密度变化很小,进而对堆芯关键参数影响很小。

Mixing flows exist in the pebble bed high temperature gas cooled reactor （HTR） because of the random characteristics of the pebble flow. The mixing then impacts the key parameters of the HTR core such as the power distribution. The impact of the mixing was analyzed quantitatively to show only a small impact of the mixing with less effect with more pebbles in the core. A mechanism is given to explain how the mixing impacts the core parameters in impact chains, including the neutron flux distribution, the depletion distribution, the fissile material distribution, and then the power distribution. The differences between the nuclear densities in different zones are quite small due to the flue sphere distribution and the pebble flow in the core with the muhi pass flue sphere making the difference smaller. Thus, the nuclear density changes in different zones of the pebble bed HTR core due to the mixed flow arc quite small with little effect on the key parameters of the reactor core.