钍射气室中钍射气子体未结合态份额和活度粒径分布的调控方法

More attention should be paid to the radiation dose caused by exposure of thoron and its progeny in China for rich thorium in the soil. Due to the unstable and inhomogeneous space distribution of thoron equilibrium factor, direct measurement of thoron progeny is the only method for assessment of the risk of thoron progeny exposure. The measurement should conclude activity concentration and size distribution of thoron progeny. Some thoron chambers have been established in China, but efficient methods of control unattached fraction and activity size distribution of thoron progeny have not been developed. In order to realize the stable and homogeneous control of unattached fraction and activity size distribution for thoron progeny, this project focuses to controlling concentration and size of carrier aerosol, unattached fraction and activity size distribution of thoron progeny in thoron chambers. This research can meet the need of the calibration of thoron progeny measurement. Futhermore, the test of measurement instruments of artificial radioactive aerosols should conclude the verification of the effectiveness of thoron progeny compensation, which also cann’t do without this study.

我国是高钍背景地区，不可忽视钍射气及其子体暴露危害。但因钍射气平衡因子空间分布的不稳定性和极不均匀性，评价钍射气子体危害只能依靠对钍射气子体的直接测量，且要测量的应是钍射气子体活度浓度与粒径分布。我国已建立了钍射气室，但没有实现对钍射气子体活度浓度与粒径分布的稳定调控。本项目通过对钍射气室载体气溶胶的调控，建立钍射气子体未结合态份额和活度粒径分布调控方法，实现对钍射气子体未结合态份额与活度粒径分布的稳定均匀调控，满足我国钍射气子体测量刻度的需要。此外，人工放射性气溶胶测量仪的测试必须包括对钍射气子体补偿有效性的检验，也同样需要开展本项目研究工作。

我国是高钍背景地区，不可忽视钍射气及其子体暴露危害。但因钍射气平衡因子空间分布的不稳定性和极不均匀性，评价钍射气子体危害只能依靠对钍射气子体的直接测量，且要测量的应是钍射气子体活度浓度与粒径分布。我国已建立了钍射气室，但没有实现对钍射气子体活度浓度与粒径分布的稳定调控。在核安全领域，我国多家单位已开发生产或正在研发用于核设施场所的人工放射性气溶胶测量仪，这类测量仪测试必须包括对钍射气子体补偿有效性的检验。本项目构建了钍射气室载体气溶胶浓度和粒径、钍射气子体未结合态份额和活度粒径的测量方法和调控方法以及相应的装置，实现了钍射气室钍射气子体未结合态份额在0.01～0.99范围内调控，钍射气子体活度粒径分布可控制在1～400nm范围内调控，钍射气子体未结合态份额和活度中值粒径能稳定均匀控制。研究结果表明钍射气室具备了模拟典型环境条件下钍射气子体分布状态特征的能力，可满足我国钍射气子体未结合态与活度粒径分布测量仪器的测试检验和人工放射性气溶胶测量仪器氡子体补偿有效性检验的需要，提升了我国钍射气子体计量水平和我国放射性气溶胶监测水平，为准确评价我国钍射气子体所致公众剂量和危害提供了技术支撑和条件保障。