241Am-Be中子参考辐射的蒙特卡罗模拟研究

研究用于校准场所中子剂量监测仪表的241Am-Be中子参考辐射场计量特性。采用蒙特卡罗方法模拟了空气自由中子参考辐射(FRNR),GB/T 14055规定的最小尺寸中子参考辐射(SRNR)和实际中子参考辐射(ARNR)中不同检验点处中子周围剂量当量率、散射中子占比和能谱分布特征。研究结果表明,空气对FRNR中的剂量率和能谱分布影响小,近似为理想中子参考辐射;采用5%含硼聚乙烯作屏蔽的最小尺寸SRNR可减少热中子,降低散射中子占比,影锥法不适用于小尺寸中子参考辐射中对散射中子的修正;ARNR中的散射中子更少、占比更低,影锥法所得散射中子占比与理论值基本一致。

Monte Carlo simulation research on reference neutron radiation of 241Am-Be radionuclide

This paper presents the study on the 241Am-Be radionuclide sources reference neutron radiation field metrology characteristics for calibrating area neutron dose monitoring instruments. The Monte Carlo method was used to simulate the neutron ambient dose equivalent rate, scattering neutron proportion and neutron energy spectrum distribution at different points of test in the air free-field reference neutron radiation (FRNR), the minimum size of standard reference neutron radiation (SRNR) specified in GB/T 14055 series standards and the actual reference neutron radiation (ARNR). The results show that air has little effect on the dose rate and energy spectrum distribution in FRNR, which is approximately an ideal reference neutron radiation; the minimum size SRNR shielded by polyethylene containing 5% boron can decrease thermal neutrons and reduce the proportion of scattered neutrons. The shadow-cone method is not suitable for the correction of scattered neutrons in small-sized reference neutron radiation; scattering neutrons in ARNR are fewer and have a lower proportion, and the proportion of scattered neutrons obtained by shadow-cone method is basically consistent with the theoretical values.