Inhalation of uranium aerosols is a concern in nuclear fuel fabrication. Determination of committed effective doses and lung equivalent doses following inhalation intake requires knowledge about aerosol characteristics; e.g., the activity median aerodynamic diameter (AMAD). Cascade impactor sampling of uranium aerosols in the breathing zone of nuclear operators was carried out at a nuclear fuel fabrication plant producing uranium dioxide via ammonium uranyl carbonate. Complementary static sampling was carried out at key process steps. Uranium on impaction substrates was measured using gross alpha counting and alpha spectrometry. Activity size distributions were evaluated for both unimodal and bimodal distributions. When a unimodal distribution was assumed, the average AMAD in the operator breathing zone at the workshops was 12.9-19.3 μm, which is larger than found in previous studies. Certain sampling occasions showed variable isotope ratios (U/U) at different impactor stages, indicating more than one population of particles; i.e., a multimodal activity size distribution. When a bimodal distribution (coarse and fine fraction) was assumed, 75-88% of the activity was associated with an AMAD of 15.2-18.9 μm (coarse fraction). Quantification of the AMAD of the fine fraction was associated with large uncertainties. Values of 1.7-7.1 μm were obtained. Static sampling at key process steps in the workshops showed AMADs of 4.9-17.2 μm, generally lower than obtained by breathing zone sampling, when a unimodal distribution was assumed. When a bimodal distribution was assumed, a smaller fraction of the activity was associated with the coarse fraction compared to breathing zone sampling. This might be due to impactor positioning during sampling and sedimentation of large particles. The average committed effective dose coefficient for breathing zone sampling and a bimodal distribution was 1.6-2.6 μSv Bq for U when Type M/S absorption parameters were assumed (5.0 μSv Bq for an AMAD of 5 μm). The corresponding lung equivalent dose coefficient was 3.6-10.7 μSv Bq (29.9 μSv Bq for an AMAD of 5 μm). The predicted urinary excretion level 100 d after inhalation intake was found to be 13-34% of that corresponding to an AMAD of 5 μm. Uranium aerosols generated at a nuclear fuel fabrication plant using ammonium uranyl carbonate route of conversion were associated with larger AMADs compared to previous work, especially when sampling of aerosols was carried out in the operator breathing zone. A bimodal activity size distribution can be used in calculations of committed effective doses and lung equivalent doses, but parameters associated with the fine fraction must be interpreted with care due to large uncertainties.

中文翻译：

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核燃料制造厂的铀气溶胶活动尺寸分布。


吸入铀气溶胶是核燃料制造中的一个问题。确定吸入后的承诺有效剂量和肺当量剂量需要了解气溶胶特性；例如，活动中值空气动力学直径（AMAD）。在通过碳酸铀酰铵生产二氧化铀的核燃料制造厂中，对核操作人员呼吸区的铀气溶胶进行了级联冲击采样。在关键工艺步骤中进行了补充静态采样。使用总α计数和α光谱测定法测量撞击基底上的铀。对单峰和双峰分布的活动规模分布进行了评估。当假设单峰分布时，车间操作员呼吸区的平均 AMAD 为 12.9-19.3 μm，这比以前的研究发现的要大。某些采样场合显示不同撞击阶段的同位素比 (U/U) 不同，表明存在不止一种粒子群；即，多模式活动规模分布。当假设双峰分布（粗颗粒和细颗粒）时，75-88% 的活性与 15.2-18.9 μm（粗颗粒）的 AMAD 相关。细粒级 AMAD 的量化存在很大的不确定性。获得1.7-7.1μm的值。车间关键工艺步骤的静态采样显示 AMAD 为 4.9-17.2 μm，通常低于假设单峰分布时通过呼吸区采样获得的结果。当假设双峰分布时，与呼吸区采样相比，较小部分的活动与粗部分相关。这可能是由于大颗粒采样和沉降过程中冲击器的定位所致。 当假设 M/S 型吸收参数时（5 μm AMAD 为 5.0 μSv Bq），呼吸区采样和双峰分布的平均承诺有效剂量系数为 1.6-2.6 μSv Bq。相应的肺当量剂量系数为3.6-10.7 μSv Bq（5 μm AMAD 为29.9 μSv Bq）。发现吸入摄入后 100 天的预测尿排泄水平为 5 μm AMAD 对应水平的 13-34%。与之前的工作相比，使用碳酸铀酰铵转化途径的核燃料制造厂产生的铀气溶胶与更大的 AMAD 相关，特别是在操作员呼吸区进行气溶胶采样时。双峰活性大小分布可用于计算承诺有效剂量和肺当量剂量，但由于存在很大的不确定性，必须谨慎解释与细分数相关的参数。