Developments of In-Situ Internal Dose Evaluation Method

本研究的目的是建立原位测定铯-137全身活度和内剂量的方法。便携式全身计数器（WBC）可以在核事故发生后的世界任何地方进行放射性人体污染的调查，即使在没有固定式全身计数器的地区也是如此。这种原位测量的新思路，有利于用单一的装置来研究土壤、食物和人之间的放射性食物链。研制了由φ76.2 × 76.2 mm NaI（Tl）闪烁体探测器、124ch小型多通道分析仪和笔记本电脑组成的新型便携式WBC系统。该探测器采用美国国家放射科学研究所（NIRS）的全身模型进行了全身铯-137测量校准。通过使用具有Ba-133和Cs-137活性的近红外甲状腺假体，也校准了甲状腺中I-131的测量。Cs-137 WBC的互比较结果良好，偏差小于10%。新型便携式白细胞白细胞系统已在世界上多个放射性危害中进行了人体和环境试验，如1954年美国比基尼核试验的朗格拉普岛，1986年白俄罗斯的科伊尼基雷杨，以及1949年以来车里雅宾斯克马亚克钚生产基地污染的车里雅宾斯克。在污染地区建立了一种重要的分析方法——本底减法。对地表和食物的测量也顺利进行，初步结果在调查结束后立即通知居民。从而达到了研究开发的目的。

The purpose of this study is to develop the technique to evaluate Cs-137 activity in the whole body and internal dose by in-situ measurement. The portable whole body counter(WBC)enables investigations of radioactive body-contamination even though in the area without the stationary WBC devise and at any place in the world after nuclear accident. This new idea on in-situ measurement has advantage to investigate radioactive food chain among soil, food and human with a single device.The new portable WBC system which has components of φ76.2 × 76.2 mm NaI(Tl)scintillator detector, a small size multi channel analyzer with 124ch and a notebook type computer, has been developed. The detector has been calibrated for measurement of Cs-137 in the whole-body by using whole-body phantom of National Institute of Radiological Sciences(NIRS). This has been calibrated also for measurement of I-131 in thyroid by using NIRS thyroid phantom with Ba-133 and Cs-137 activities. The intercomparison of Cs-137 WBC shows a good result with a bias less than 10%.The new portable WBC system has been tested for people and environment in several radiological hazards in the wortd, such Rongelap Island suffered from USA nuclear tests at Bikini 1954, Khoyniki Rayon Belarus suffered from Chernobyl accident 1986 and Chelyabinsk suffered from pollution of Mayak plutonium production complex since 1949. The important analytical method has been established such background subtraction in contaminated territory. The measurements on ground surface and food were also successfully carried out, and the preliminary results were informed to residents just after the investigations. Therefor the purpose of the research and development was achieved.