装饰装修用石材所致室内γ外照射剂量率的估算方法研究

Estimation of the indoor external γ-dose rate from decorative stones

目的 建立更加准确估算装饰装修用石材所致室内γ外照射剂量率的方法.方法 结合室内空间模型和装饰装修情况,基于Monte Carlo方法计算铺设不同面积和厚度石材后室内离地1 m中心处的外照射剂量率和剂量率转换系数,并开展实验测量验证;结合计算结果,进一步探讨装饰装修用石材的放射性含量限值.结果 在同一室内,随着石材铺设厚度或面积增加,石材中放射性核素所致室内γ剂量率随之增大.在相同铺设面积条件下,剂量率转换系数随铺设厚度近似线性增加;在相同铺设厚度条件下,剂量率转换系数随铺设面积增加而增加,但增加呈减缓趋势.在铺设相同石材情况下,房间越小,γ剂量率增加越大.模拟计算值与实测结果在±20％以内吻合.结论 装饰装修用石材所致室内γ外照射剂量率的增加不仅与石材中的放射性核素含量有关,而且还依赖于石材的铺设面积、厚度以及房间大小.本研究的计算方法可更加准确估算出装饰装修石材所致居民的附加外照射剂量,可为修订装饰装修材料中放射性核素含量限值标准提供理论依据.

Objective To establish an accurate method for estimating the indoor gamma dose rate from decorative stones.Methods Combining a room model with decorating conditions,the gamma dose rates and dose rate conversion factors （DCF） at 1 m above the floor in the room center were calculated with the Monte Carlo simulations,and the calculation results were verified through experiments.Based on the results,the limit of radionuclide contents in stone materials was further discussed.Results The DCF increases with the increase of area or thickness of decorative stones in the same room.The increase of DCF with the thickness of decorative stone is approximately linear.The DCF also increases with the area of decorative stones,but the increasing trend slows down.For the same decorative stones,the smaller the room,the larger the increase of gamma dose rate.Experimental results were consistent with the simulation results within ± 20％.Conclusions The increase of indoor gamma dose rate depends not only on the radionuclide contents,but also on the area and thickness of the decorative stones as well as the room size.The method used in this study can be used to estimate,more accurately than ever,the additional external exposure to residents due to decorative stones,and it provides a theoretical basis for revising the limit standard on radionuclide contents in decorative materials.