阳江高本底地区居民器官剂量学研究

发布时间：2018-02-26 19:34

本文关键词： 高本底小剂量 γ能谱无源效率刻度器官剂量外照射　出处：《中国疾病预防控制中心》2012年硕士论文　论文类型：学位论文

【摘要】：为了研究长期小剂量、低剂量率电离辐射对人体健康的影响,特别是小剂量电离辐射对不同部位患癌危险度的影响,阳江天然高本底地区天然放射性高本底辐射与居民健康研究已经开展了近40年,辐射剂量学的研究伴随整个研究过程,也已取得较多的剂量学测量数据,本研究作为阳江天然高本底地区剂量学研究的延续,探寻外照射所致居民器官剂量学研究的新方法,以期对器官剂量进行较为准确的估算,以更好的分析剂量——效应关系。本研究使用ORTEC DETECTIVE-DX-100T型HPGe γ能谱仪对高本底地区和对照地区居民所处环境Y能谱的测量,根据照射的实际情况经过适当简化,建立适当的照射模型,模拟实际环境对居民的辐射照射情况,通过无源效率刻度的方法计算所建立的照射模型下γ能谱仪探头的探测效率刻度曲线,经过γ能谱解谱分析(能量刻度选择天然放射性核素6个能量点进行刻度,效率刻度使用无源效率刻度软件对所用照射模型下的刻度曲线进行计算),计算出该模型中核素的分布、构成以及各自活度。根据模型的空间结构和核素的活度计算出参考点(相对于模型中HPGeγ能谱仪晶体中心)处的空气比释动能率,最后根据照射的实际情况确定照射的几何条件,选用适当的单位空气比释动能到器官吸收剂量的转换系数计算出不同器官的吸收剂量。根据高本底地区剂量学调查中划分的高、中、低剂量组和对照组共4个剂量组,分组选取4个镇的1到2个村庄作为研究对象,对照地区选取高本底地区剂量学调查结果中年吸收剂量最低的村庄,高本底地区高、中、低剂量组选取年吸收剂量在该组中的最高的村庄,以尽量拉开各剂量组间的差别。每个剂量组选取建筑材料为土、石头、砖的住宅各4间分别进行测量(部分村庄由于实际条件限制土房和石头房不足4间),每个剂量组选取一个室外测量点进行测量。整个研究共对46个测量点进行了现场Y能谱的测量,其中高本底地区室内30个点、室外3个点,对照地区室内12个点、室外1个点。每个剂量组室外测量点进行土壤样品的采集并进行实验室γ能谱分析,确定土壤中天然放射性核素的构成。另外,所有的测量点均使用6150AD6/h+6150AD b/h型便携X/γ剂量率仪对测量点的剂量率进行了测量,测量结果与γ能谱方法计算结果进行验证。通过γ能谱方法所计算的空气比释动能率和X/γ剂量率仪所测得的剂量率归一到同一物理量进行统计分析,结果表明分析结果很好的符合了实际照射条件和所建立的照射模型的一致性,证实了对实际照射条件进行简化的可行性。本研究使用γ能谱方法,分析出圆柱形有底面源模型和圆面源模型中天然放射性核素的构成及活度,使用CRAM模型ROT照射几何条件的转换系数,结合以往流行病调查中的居民居室内居留因子(0.698),计算了外照射所致阳江高本底地区和对照地区各剂量组不同类型住宅的居民器官吸收剂量和全身有效剂量。
[Abstract]:In order to study the long-term small dose, low dose rate effects of ionizing radiation on human health, especially small doses of ionizing radiation effect on cancer risk in different parts of the Yangjiang natural high background area of high natural background radiation and health of residents has been carried out for nearly 40 years, the research of radiation dosimetry with the entire course of the study. It has been made more dosimetric measurement data, this study as a natural continuation of the high background of Yangjiang dosimetric study area, to explore a new method to study the dosimetric external irradiation caused by the residents, in order to estimate the organ dose for more accurate, to better analyze the dose effect relationship.
This study uses the ORTEC DETECTIVE-DX-100T type HPGe gamma spectrometer to measure the high background area and control area residents environment Y spectrum, according to the actual situation of irradiation after appropriate simplification, establish a proper model for simulation of radiation exposure, exposure to the residents of the actual environment, the detection efficiency calibration curve model established by irradiation method sourcelessefficiencycalibration calculated the gamma ray spectrometer probe, the gamma ray spectrum analysis (energy scale selection of natural radionuclide 6 energy points scale, efficiency calibration using passive efficiency calibration software for calibration curve is calculated under the irradiation model), calculate the distribution of radionuclide in the model. Composition and their activity. The calculated reference points according to the spatial structure and activity model of nuclide (relative to the model HPGe gamma spectrometer crystal center) at the air kerma rate, the most The geometric condition of irradiation is determined according to the actual situation of radiation. The absorbed dose of different organs is calculated by selecting the appropriate conversion coefficient of the unit air specific kinetic energy to the organ absorbed dose.
According to the high background area investigation division of the high dose, and low dose group and control group were 4 dose group, grouping and selecting 4 towns 1 to 2 villages as the research object, the control area from HBRA dosimetric survey results of middle-aged village lowest absorption dose, high background area. In the low dose group selected years absorbed dose in the group with the highest village, to try to pull the difference between each dose group. Each dose group selected building materials for soil, stone, brick houses of the 4 measured (part of the village due to lack of actual conditions and a 4 room stone house) each group selected a dose, the outdoor measurement spot. The research includes the measurement of Y spectrum of 46 measurement points, the high background area indoor 30 points, outdoor 3 points, 12 points control area indoor, outdoor 1 points. Each dose group of outdoor Spectrum analysis laboratory measurement points of soil samples collected and determine the composition of natural radionuclides in soil. In addition, all measurement points are used 6150AD6/h+6150AD b/h type portable X/ gamma dose rate instrument of measuring points were measured, the measurement results with the gamma spectrum method was validated.
By gamma spectrum method calculation of the air kerma rate and X/ dose rate meter measured the gamma dose rate was normalized to the same physical quantity statistical analysis, results show that the results fit well with the consistency of the actual conditions and the irradiation irradiation model, proved the feasibility of the actual conditions the irradiation was simplified.
This study uses the gamma spectrum analysis method, composition and activity of natural radionuclide bottomed cylindrical surface source model and the round surface source model, the conversion coefficient using the CRAM model ROT irradiation geometry conditions, combined with previous epidemiological survey of residents living within the residence factor (0.698), external radiation caused by the high background radiation area of Yangjiang and the control groups of different types of residential area residents organ absorbed dose and effective dose were calculated.

【学位授予单位】：中国疾病预防控制中心
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R144

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