中国传统房屋^(220)Rn平衡因子的研究

Study on ^(220)Rn Equilibrium Factor in China Traditional Dwellings

本文对中国传统土结构房屋中220Rn浓度(CTn)及其子体浓度(Cp,Tn)的空间分布与季节变化进行了测量。结果显示,CTn的空间分布有明显的浓度梯度变化,与发生源(裸露的墙面和地面)的距离呈指数衰减,同时存在较好线性关系和可重复性。CTn的季节变化是秋季高,冬春季低,季均值与年均值的相对偏差与222Rn接近。Cp,Tn的季节变化类似于CTn和Cp,Rn,其空间变化可忽略。固定220Rn的测量距离,CTn与Cp,Tn间有明确的关系。距墙2.5 cm和20 cm得到的220Rn的平衡因子(FTn)分别为0.003±0.001和0.017±0.014。经验证,Cp,Tn的实测结果与采用FTn的估算结果符合较好。相对于220Rn子体,220Rn浓度的测量更易实现,FTn的引用为室内220Rn剂量评价提供了一个简单可靠的方法。

The spatial distribution and seasonal variation of 220Rn concentration（CTn） and its progeny concentration（Cp,Tn） in China traditional dwellings constructed with soil were studied.The results show that the spatial distribution of CTn appears a significant concentration gradient,and decreases exponentially from the distance of source（bare walls or ground）,while there is a good linearity and repeatability.The seasonal variation of CTn displays maximum value in autumn and minimum value in winter.The seasonal variation of Cp,Tn comparing with CTn and Cp,Rn is similar,and its spatial variation can be ignored.Therefore,fixing the distance of 220Rn form source,there is a definite relationship between CTn and Cp,Tn.220Rn equilibrium factors FTn respectively are 0.003±0.001 and 0.017 ± 0.014 at the distances of 2.5 cm and 20 cm from wall.The Cp,Tn results of actual measurement in traditional houses are in good agreement with the calculated values by using FTn.The measurement to 220Rn gas is more easily achieved comparing with 220Rn progenies.The introduction of FTn provides a simple and reliable method for assessment of 220Rn exposure.