Button T M, Hamilton R G
Health Phys. 1982 Dec;43(6):853-7. doi: 10.1097/00004032-198212000-00007.
Regulatory agencies have recently placed emphasis upon quantification of 125I released to the environment during protein iodinations at radioiodination facilities. This necessitates air sampling in order to determine the concentration of 125I in the effluent. Air sample trapping mechanisms generally employed are activated charcoal filters. Difficulty arises in quantifying the activity of 125I trapped because of the attenuation of the 125I decay photons by the charcoal. Evaluation of the activity incident upon commercially available filters using a scintillation detector and large detector source separation is considered here. It is demonstrated that the activity in the filter may be treated as an exponential distribution within an attentuating matrix. This treatment essentially adds a constant correction factor to the counting efficiency of a given geometry for a filter-affluent flow rate combination. Finally, it is shown that an approximation assuming a uniform distribution of activity produces a large error in correction factor to the counting efficiency for the filters examined.
监管机构最近强调要对放射性碘化设施进行蛋白质碘化过程中释放到环境中的¹²⁵I进行量化。这就需要进行空气采样，以确定排放物中¹²⁵I的浓度。一般采用的空气样品捕集机制是活性炭过滤器。由于¹²⁵I衰变光子会被活性炭衰减，因此在量化捕获的¹²⁵I的活度时会出现困难。本文考虑使用闪烁探测器和大探测器源分离来评估入射到市售过滤器上的活度。结果表明，过滤器中的活度在衰减矩阵内可视为指数分布。这种处理本质上是为给定几何形状与过滤器 - 流出物流量组合的计数效率添加一个恒定的校正因子。最后，结果表明，假设活度均匀分布的近似方法会在所研究的过滤器的计数效率校正因子中产生很大误差。
