建筑材料致居民辐射剂量模型及氡射气系数快速测量方法研究

发布时间：2018-03-19 15:53

本文选题：建筑材料　切入点：居民辐射剂量模型　出处：《中国疾病预防控制中心》2014年博士论文　论文类型：学位论文

【摘要】：背景近年来,随着我国工业化和城镇化进程的不断加快,建材的需求量越来越大。此外,“节能减排、保护资源”等政策的实施,导致掺渣、多孔的新型建材迅速发展,并广泛应用于房屋建造。然而,由于制造工艺、生产原料等的巨大变化,新型建材的密度、厚度以及氡射气系数也与传统建材产生较大差别,可能导致利用传统的建材致居民辐射剂量模型估算的居民剂量负担产生一定的偏差,不利于有效保护居民健康,也可能阻碍新型建材的科学发展和工业废渣的合理利用。目的研究、分析建材的密度、厚度、类型以及居室内剂量参考点、氡射气系数等参数对估算建材致居民辐射剂量的影响,确定权重大的影响参数并探讨修正方法,统筹考虑内、外照射剂量,建立一种新的建材致居民辐射剂量模型,以更准确评价建材放射性危害。对引入模型中的氡射气系数,研究建立一种快速测量方法,以提高检测效率。研究加气混凝土砌块的氡射气系数随含水率、温度和湿度的变化规律。方法 (1)基于Monte Carlo方法,利用MCNPX程序,建立典型的居室结构(4m×5m×2.8m,带门窗),在居室4面墙、底和顶分别填充不同类型、密度和厚度的建材时,模拟计算居民比有效剂量率。利用非线性回归分析,拟合居民比有效剂量率与表面密度的关系函数,从而建立一种新的建材致居民外照射剂量模型,并通过现场测量验证可靠性。通过对建材中氡输运机理进行分析,获得室内氡浓度与建材氡射气系数、密度和厚度的函数关系,建立建材致居民内照射剂量估算模型。 (2)通过对氡射气在建材内部和密闭腔体中输运规律的分析,推导氡射气系数快速测量的数学方程。以加气混凝土砌块为研究对象,利用连续测氡仪、密闭腔体和真空封泥等,确定最优化测量时间、分析样品厚度的影响以及该方法的复现性。通过与标准的长时间累积测量法进行比对,验证快速测量方法的可靠性。 (3)根据建立的氡射气快速测量方法,测量加气混凝土砌块的氡射气系数在不同含水率(0%、2%、5%、10%、20%、25%、30%、35%、40%、45%、53%和60%)、温度(10、17、20、25、30、35和40℃)和相对湿度(12%、33%、60%、79%和95%)条件下的氡射气系数；并对氡射气系数的测量结果进行回归分析,探讨氡射气系数与含水率、温度和湿度的变化规律。结果 (1)建材的类型、室内剂量参考点位置对居民剂量无显著性影响。建材的厚度、密度和氡射气系数对居民辐射剂量影响较为显著,应进行修正。建材中40K、238U系和232Th系放射性核素致居民外照射比有效剂量率随着建材表面密度(密度与厚度的乘积)的增加呈对数型增长。 (2)统筹考虑建材致居民内、外照射剂量,引入厚度、密度、氡射气系数,建立了建材致居民辐射剂量模型：式中,E为建材致居民有效剂量率,nSv·h-1；Ck,CRa和CTh分别为建材中40K、238U系和232Th系放射性核素致居民比有效剂量率值,(nSv·h-1).(Bq·kg-1)-1； Ak、AR。和ATh分别为建材中40K、226Ra和232Th的比活度,Bq.kg-1;ε为建材氡射气系数；Ρ为建材密度,kg·m-3；d为建材厚度,m。其中,外照射剂量模型经现场测量验证,具有较好的可靠性。 (3)建材氡射气系数的快速测量研究中,24-60h的测量结果较稳定,可作为最优化测量时间。6次重复测量结果的平均值±标准偏差为0.153±0.007,变异系数为4.6%,表明具有较好的重复性。在样品厚度小于氡扩散长度的0.4倍时,不同厚度样品的测量结果没有显著性差异(P0.05)。氡射气系数的快速测量结果与标准累积测量结果没有显著性差异(P0.05)。 (4)加气混凝土砌块的氡射气系数随着其含水率的增加呈对数型增长：ε=0.096.1n(s+2.43)+0.037(R2=0.952)；加气混凝土砌块的氡射气系数随着其含水率的增加呈线性增长：ε=0.00245.T+0.0601(R2=0.987);不同湿度下,加气混凝土的氡射气系数测量结果无显著性差异(P0.05)。结论本课题通过分析建材厚度、密度和氡射气系数等对建材致居民辐射剂量模型的影响,确定权重大的影响参数并探讨修正方法,统筹考虑居民所受内、外照射剂量,建立一种新的建材致居民辐射剂量模型。所建剂量模型可更合理、准确估算建材致居民辐射剂量,为评价建材放射性危害提供剂量学基础；指导建材安全选用,为制、修订建材放射性危害评价与控制体系提供科学依据；在有效保护居民身体健康的同时,也可促进新型建筑材料的科学发展、工业废渣的合理利用。研究建立建材氡射气系数的快速测量方法,较大缩短测量时间。可提高检测效率、降低检测成本,在促进辐射防护检测技术发展的同时,也是新建剂量模型在实际中推广应用的一种有益补充。
[Abstract]:background
In recent years, with China's industrialization and urbanization continues to accelerate, more and more demand for building materials. In addition, the implementation of energy-saving emission reduction, resource conservation and other policies, lead slag, porous new building materials is developing rapidly, and is widely used in building construction. However, due to the manufacturing process, great changes in production raw materials, new building materials of the density, thickness and radon emanation coefficient have great difference with the traditional building materials, may lead to dose burden using traditional building materials to residents of radiation dose estimation model has certain deviation, is not conducive to the effective protection of the health of residents, rational use of new building materials may also hinder the development of science and industrial waste residue.
objective
Study on the analysis of building materials, density, thickness, type and room dose reference point, effect of radon emanation coefficient on the estimation of building materials to residents of the radiation dose, and to explore the correct method to determine the parameters of right significant impact on overall consideration, the dose of external irradiation, the establishment of a new residential building materials induced by radiation dose model. In order to more accurately evaluate the hazards of radioactive materials. The introduction of radon emanation coefficient in the model, study the establishment of a fast measurement method to improve the detection efficiency. The radon emanation coefficient of aerated concrete block with moisture content, temperature and humidity.
Method
(1) Monte Carlo based on the method of using the MCNPX program, a typical structure of the room (4m * 5m * 2.8m, with windows and doors), in room 4 wall, bottom and top are respectively filled with different types, density and thickness of materials, simulation of residents than the effective dose rate. By using nonlinear regression analysis, fitting residents than the relationship between the effective dose rate function and surface density, thus establishing a kind of new building materials to the residents of the external dose model, and through the field measurement reliability. Through the analysis of the mechanism of transport transport of radon in building materials, building materials for indoor radon and radon emanation coefficient, the function relationship between the density and thickness of the building, building materials the resident internal dose estimation model.
(2) based on the analysis of radon transport rule in building materials inside and in a sealed cavity, the mathematical equations are fast measurement of radon emanation coefficient. The aerated concrete block as the research object, using continuous radon measurement instrument, a sealed cavity and vacuum cement, determine the optimal measurement, analysis of influence of the thickness of the sample and the reproducibility of the method. By comparison with the standard long time cumulative measurement method, the reliability of rapid measurement method of verification.
(3) according to the rapid measurement method of radon establishment, radon emanation coefficient measurement of aerated concrete block in different water content (0%, 2%, 5%, 10%, 20%, 25%, 30%, 35%, 40%, 45%, 53% and 60% (10,17,20,25,30,35), temperature and relative humidity (40 DEG C) and 12% 33%, 60%, 79%, and 95%) radon emanation coefficient conditions; and the measurement results of radon emanation coefficient of regression analysis on coefficient of gas and water radon emission rate, temperature and humidity.
Result
(1) the type of building materials, indoor location dose reference point has no significant impact on the residents' dose. The thickness of building materials, and the density of radon emanation coefficient of residents radiation dose more significant effect, should be corrected. The building of 40K, 238U and 232Th radionuclide induced by external irradiation than residents effective dose rate with the density of building materials the surface (the product of density and thickness) showed a logarithmic growth.
(2) the radiation dose model of building materials is established by considering the dosage of building materials, the dose of external irradiation, and the introduction of thickness, density and radon ejection coefficient.
In the formula, E is building the resident effective dose rate, nSv, H-1; Ck, CRa and CTh respectively in building materials 40K, 238U and 232Th induced by radionuclide residents than the effective dose rate values (nSv, h-1). (Bq, kg-1) -1; Ak, AR. and ATh respectively in building materials 40K, 226Ra and 232Th than live, Bq.kg-1; E as building materials radon emanation coefficient; P for building density, kg, M-3; D for building materials thickness, M.
Among them, the external irradiation dose model is verified by field measurement, and it has good reliability.
(3) measurement of building materials radon emanation coefficient in the measurement results of 24-60h was stable, the average value can be used as optimal measuring time.6 repeated measurements. The standard deviation was 0.153 + 0.007, the coefficient of variation was 4.6%, show that it has good repeatability. At 0.4 times the thickness of the sample is less than the length of the radon diffusion when the measurement results of samples with different thickness had no significant difference (P0.05). The results of rapid measurement of radon emanation coefficient and cumulative measurement results of no significant difference (P0.05).
(4) the radon emanation coefficient of the aerated concrete block with the increase of water content in logarithm growth: epsilon =0.096.1n (s+2.43) +0.037 (R2=0.952); radon emanation coefficient of the aerated concrete block grows linearly with increase in moisture content: epsilon =0.00245.T+0.0601 (R2=0.987); under different humidity, no significant difference radon emanation coefficient measurement results of aerated concrete (P0.05).
conclusion
This paper analyzes the influence of building material thickness, density and radon emanation coefficient caused by the radiation dose model of building materials for the residents, and to explore the correct method to determine the parameters of the right to the major influence, residents and consider the internal and external exposure dose, the establishment of a new residential building materials induced by radiation dose model. The dose model more reasonable and accurate estimation of radiation dose to residents of building materials, building materials for the evaluation of radioactive damage dosimetric basis; safety guidance for selection of building materials, building materials, provide a scientific basis for the revision of radioactive hazard evaluation and control system; the effective protection of the health of residents at the same time, also can promote the scientific development of new building materials, reasonable utilization of industrial waste residue.
The rapid measurement method of radon emanation coefficient of building materials is studied, which can greatly shorten the measuring time. It can improve the detection efficiency and reduce the cost of detection, while promoting the development of radiation protection detection technology, and it is also a useful supplement to the application of the new dose model in practice.

【学位授予单位】：中国疾病预防控制中心
【学位级别】：博士
【学位授予年份】：2014
【分类号】：R144.1

【参考文献】