Abstract A portable thyroid dose monitoring system has been developed at the Japan Atomic Energy Agency (JAEA) to assess the thyroid equivalent dose for workers and members of the public in a high dose rate environment. The background (B.G.) photon correction is required for an accurate measurement in a high dose rate environment at an early stage after a nuclear accident. The responses of the system to the B.G. photons were calculated with the simplified cylindrical phantoms made of PMMA or the voxel phantoms using the PHITS code. Then they were compared each other among the respective age groups. It was found that the cylindrical phantom with an appropriate size and properly arrangement can mimic the human body in the high dose rate caused by 131I sources. As such we successfully developed the B.G. photon correction method using the cylindrical phantoms; one of those is used as an effective way to calibrate the monitoring system by inserting a133Ba point source into it. As an additional phantom is not required, this method has a great advantage in the practical operation of the B.G. photon correction.

中文翻译：

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在高剂量率环境下使用 JAEA 开发的使用伽马射线光谱仪的便携式甲状腺剂量监测仪的背景校正方法

摘要 日本原子能开发署 (JAEA) 开发了一种便携式甲状腺剂量监测系统，用于评估高剂量率环境中工作人员和公众的甲状腺当量剂量。为了在核事故后的早期阶段在高剂量率环境中进行准确测量，需要进行背景（BG）光子校正。系统对 BG 光子的响应使用由 PMMA 制成的简化圆柱体模或使用 PHITS 代码的体素体模进行计算。然后他们在各自的年龄组之间相互比较。发现尺寸合适、排列合理的圆柱体模可以模拟131I源引起的高剂量率下的人体。因此，我们成功开发了 BG 使用圆柱体模的光子校正方法；其中之一是通过在其中插入a133Ba点源来校准监控系统的有效方法。由于不需要额外的体模，这种方法在BG光子校正的实际操作中具有很大的优势。