Developments of In-Situ Internal Dose Evaluation Method

本研究的目的是发展一种原位测量全身~（137）Cs活度和内照射剂量的技术。便携式全身计数器（WBC）可以在没有固定WBC装置的地区和核事故发生后的世界任何地方进行放射性人体污染调查。本文介绍了一种由φ76.2 × 76.2mmNaI（Tl）闪烁体探测器、124通道小型多道分析仪和笔记本电脑组成的便携式WBC系统。该探测器已被校准用于测量全身中的Cs-137，使用的全身体模的国立放射科学研究所（NIRS）。这也已被校准，用于通过使用具有Ba-133和Cs-137活性的NIRS甲状腺体模测量甲状腺中的I-131。Cs-137白细胞计数的比对结果表明，该仪器的误差小于10%。该仪器已在世界上几个放射性危害地区进行了人体和环境的检测，如1954年美国在比基尼岛进行核试验的朗格拉普岛，1986年，白俄罗斯的霍伊尼基区发生了切尔诺贝利事故，车里雅宾斯克自1949年以来一直受到玛雅克钚生产综合体的污染。背景扣除法已成为污染区的重要分析方法。地面和食物的测量也成功地进行了，初步结果在调查后立即通知了居民。从而达到了研究和开发的目的。

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.