Abstract FASTSCAN (Canberra, Meriden, CT, USA), a standing-type whole-body counter with upper and lower NaI(Tl) detectors, has been mostly used to determine local residents’ level of internal contamination with 134/137Cs following the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster in 2011. In the present study, we performed Monte-Carlo simulations with age-specific mathematical human phantoms to investigate the counting efficiencies of the FASTSCAN counter for 131I thyroid measurements. As a result, although the lower detector had low sensitivity for 131I in the thyroids of the adult and 15 y phantoms as well as the 10 y phantom standing on a 30-cm-high stool, the response of this detector may be used as an indicator of surface contamination overlooked on a subject. The total counting efficiency investigated in this study was 0.017–0.018 (cps/Bq) among all age groups. Based on this sensitivity, the determination level for thyroid activity could be calculated to be ~300 Bq under the slightly elevated background radiation level observed after the FDNPP disaster.

中文翻译：

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用数学模型进行蒙特卡罗模拟，以研究全身计数器对甲状腺测量的有效性

摘要 FASTSCAN (Canberra, Meriden, CT, USA) 是一种带有上下 NaI(Tl) 探测器的立式全身计数器，主要用于确定福岛核事故后当地居民的 134/137C 内部污染水平。 2011 年第一核电站 (FDNPP) 灾难。在本研究中，我们使用特定年龄的数学人体模型进行蒙特卡罗模拟，以研究 FASTSCAN 计数器对 131I 甲状腺测量的计数效率。因此，虽然下探测器对成人甲状腺中的 131I 和 15 年体模以及站在 30 厘米高凳子上的 10 年体模的灵敏度较低，但该探测器的响应可用作被忽视的表面污染指标。本研究中调查的总计数效率为 0.017-0。018 (cps/Bq) 在所有年龄组中。基于这种敏感性，在 FDNPP 灾难后观察到的略微升高的背景辐射水平下，甲状腺活动的测定水平可以计算为~300 Bq。