CMRR冷中子源中子物理参数模拟计算

Neutron physical parameter's simulation of CMRR cold neutron source

为给中子导管中子输运与屏蔽计算提供输入参数,建立冷中子源(Cold Neutron Source,CNS)模型,制作正氢与仲氢蒙特卡罗(Monte Carlo N particle transport code,MCNP)截面数据库,计算了慢化室内不同穿透深度的中子注量率变化趋势、冷中子(Cold Neutron,CN)孔道入口处中子角分布与冷中子增益、中子导管入口处中子角分布与中子注量率空间分布。结果显示,液氢慢化剂使中子束内冷中子有显著的增益,随着中子在CN孔道内的传输中子束的准直性大大提高,为下一步开展中子导管计算提供了重要参考数据。

[Background] Cold neutron is generally yielded by cold neutron source （CNS） in large-size neutron source. The wavelength of cold neutron is similar to that of molecular or atomic structure of lots of materials, which could be adopted to study material macroscopical or macroscopic structure. [Purpose] This paper aims to provide input data for neutron transportation in neutron guide and shielding calculation of China Mianyang Research Reactor （CMRR）. [Methods] CNS was modeled, and ortho-hydrogen and para-hydrogen Monte Carlo database was processed. We calculated the neutron flux in different depths inside the liquid hydrogen moderator, neutron angular distribution and cold neutron gain in the cold neutron （CN） channel＇s entrance, and got the neutron angular and spatial distributions at the intake of neutron guide. [Results] The results showed that liquid hydrogen could enhance the cold neutron gain, and neutron beam collimation was promoted by CN horizontal channel. [Conclusion] The calculation indicates CNS may significantly improve the performance of neutron beam.