In-vivo lung monitoring is an important technique for the assessment of internal dose of radiation workers handling actinides. At BARC, counting efficiencies (CEs) of detection systems used for estimation of natural uranium in the lungs are evaluated using realistic thorax physical phantoms or computational voxel phantoms. The quantification of ²³⁸U and ²³⁵U in lungs is done using CEs determined at 63.3 keV and 185.7 keV photon energies respectively. These CEs can also be used for assessment of enriched uranium in the lungs of the workers. In this study, spectra are generated for HPGe array detectors using Monte Carlo simulations of various enriched uranium compositions distributed in the lungs of thorax voxel phantom. A methodology is developed to predict the ²³⁵U enrichment from lung spectrum analysis using the ratio of net counts in 185.7 keV and 63.3 keV energy regions. It is possible to estimate enrichments in the range of 2%–30% using the developed method with less than ±9% error. Finally, effect of ²³⁵U enrichment on dose assessment using lung monitoring method is studied.

体内肺监测是评估辐射工作人员处理锕系元素内部剂量的一项重要技术。在 BARC，用于估计肺部天然铀的检测系统的计数效率 (CE) 使用真实的胸部物理模型或计算体素模型进行评估。肺中²³⁸ U 和²³⁵ U的量化是使用分别在 63.3 keV 和 185.7 keV 光子能量下确定的 CE 完成的。这些 CE 还可用于评估工人肺部的浓缩铀。在这项研究中，使用分布在胸部体素幻影肺部的各种浓缩铀成分的蒙特卡罗模拟，为 HPGe 阵列探测器生成了光谱。开发了一种方法来预测²³⁵使用 185.7 keV 和 63.3 keV 能量区域的净计数比率从肺光谱分析中富集 U。使用开发的方法可以估计 2%–30% 范围内的富集，误差小于 ±9%。最后，研究了²³⁵ U 富集对使用肺监测方法进行剂量评估的影响。