室内氡浓度的非线性分析

氡是一种天然放射性气体,其中室内氡与人类健康密切相关,室内氡浓度成为公众关注的问题之一。假定室内外空气中氡及氡子体均一混合的前提下,推导出一个关于室内氡浓度计算的模型,据此计算室内氡浓度。结果表明：室内氡浓度随时间和通风量系数的增加,趋向一个稳定的值,最终达到室内外氡浓度平衡。该模型计算出的室内氡浓度理论值（6.35～40 Bq/m 3）与任天山和王玫等的实测结果（6～50 Bq/m 3）一致,表明模型可靠。     

夏冬两季室内通风降氡能耗分析

通过对室内氡的来源及氡浓度平衡的分析,建立了室内氡浓度的估算模型。在此基础上,建立了通风降氡能耗与室内氡浓度之间的计算模型,对空调房间内冬夏两季通风降氡能耗和通风换气率进行模拟。通过通风换气率整合两个模型,模拟得出室内通风降氡能耗与室内氡浓度二者之间的关系。以湖南省衡阳市住房进行模拟分析,分析结果表明,室内通风降氡能耗随着室内氡浓度降呈指数类增长,当室内氡浓度值较低时,空调通风降氡能耗要高于高浓度时降低相同氡浓度时所需能耗。     

广州市室内氡浓度调查报告

我公司于2008～2009年承担了全国室内氡调查项目中广州地区的调查工作。本次调查中,按全国室内氡浓度调查方案的要求,按行政区、人口分布、建筑物和种类等分布了采样点,共布了146个采样盒,回收了135个。结果表明,广州市室内氡平均浓度为32.70Bq/m3,最大值156Bq/m3,最小值4Bq/m3。这次全国10个城市室内氡浓度调查结果的均值为34.9Bq/m3。在广州室内氡调查结果比较低的主要原因是人们长期开窗通风的生活习惯。与工程验收检测的氡浓度相差甚远,主要的原因是检测时的状态不同。     

广州新建住宅室内氡浓度调查

采用活性炭盒法测量广州地区新建住宅楼室内氡浓度,在对1796个样本进行统计后得到近年来新建住宅室内氡浓度平均值为84.2Bq/m~3,在检测房间中有3%的房间室内氡浓度大于200Bq/m~3。土壤氡浓度对高层住宅室内氡的影响不大。室内氡浓度检测时的状态不同,检测结果也完全不同。     

中国锦屏地下实验室空气氡浓度监测(2010—2011)

为评估中国锦屏地下实验室的氡本底辐射环境对稀有物理事件探测实验及极低本底伽玛能谱测量装置的影响,使用测氡仪对实验大厅的空气氡浓度进行了跨度为10个月(134d)的实时监测。监测数据显示:在无通风情况下,实验大厅空气氡浓度平均值为101Bq·m-3,波动范围为60~149Bq·m-3;在通风情况下,实验大厅空气氡浓度平均值为86Bq·m-3,波动范围为19~179Bq·m-3;与国际地下实验室相比,中国锦屏地下实验室的空气氡浓度处于平均水平,能够保证各低本底实验的正常运行。     

河北省遵化市居室内氡浓度调查

通过对河北省遵化市60个城镇居室内氡浓度测量表明：居室内氡浓度变化范围在15.5Bq/m3~180Bq/m3,平均52±25Bq/m3,比全国平均氡浓度高。居民所受氡照射剂量1.31mSv/a.     

夜间室内CO_2浓度与新风量关系的实测研究

本文以南京某住宅建筑为研究对象,进行卧室内睡眠和静坐条件下CO_2浓度与新风量关系实际测试。分析了稀释通风下新风量和人员状态对夜晚卧室CO_2浓度的影响。结果显示,稀释通风下,成年人睡眠时最小新风量应不低于20 m~3/(h·p),即换气次数应达到1.1次/h。静坐时,其最小新风量还应在此基础上增加20%。     

防辐射涂料

本涂料不仅具有屏蔽室内建材氡析出率、降低室内氡浓度的功能,而且具有装饰功能。因而它是净化、美化室内环境的新型涂料。1)主要性能指标防辐射性能:屏蔽氡的效率>90%;屏蔽241Amγ射线效率为9.3%;屏蔽室内γ射线的效率为1.3%。建筑性能:遮盖力250～280g/c。耐水性:自然水浸泡96h无变化。耐擦洗性:≥50次。白度>80。2)适用范围①建材中放射性物质镭-226,钍-232含量较高的建筑场所;②为节能保温长期关门窗的北方地区;③通风不良的地下旅馆、餐厅、娱乐场所。3)效益分析氡在美国是肺癌的第二位诱因,估计每年导致14000人死亡,美国鼓励采用降低…     

地下工程中氡及空气离子环境急待改善

通过对我国五个地区的37个地下工程的空气离子环境和氡水平的测试及试验研究表明;投入正常使用的地下工程,特别是人员较多的掩土工程空气离子环境较差,空气负离子浓度的均值只有201个/cm~3,单极性系数均值高达2.0。大气尘,水分子团等空气中悬浮的凝结核均是空气离子的消失因素,通风空调系统与设备也消耗大量的空气离子。地下工程中氧及其子体虽然是空气离子的产生因素,但由于较高的氡水平对人体有害,必须按“放射卫生标准”使之保持在一定的水平之下。文中给出了空气负离子浓度、氧浓度和含尘量间关系的回归曲线,提出了改善地下工程空气离子环境的有效措施是:降低空气中含尘量和湿度,并适当安装空气负离子发生器。地下工程中氧水平一般比地面室内高一个数量级以上,地下工程中工作人员因吸入氡子体所致剂量限值应为3msv,氡子体导出空气浓度应为93Bq/m~3,在所测使用地下工程中超出此标准的工程占54%,工作人员因吸入氡子体所致年有效剂量均值为3.92msv,是限值(3msv)的131%。地下工程中降低氡水平的经济有效措施是通风换气,文中给出了估算氡平均析出率和防氡通风率的简单、易行、实用的方法,并编制了地下工程防氡通风率估算表。     

夏热冬冷地区中小学绿色建筑通风设计探讨

中小学建筑作为青少年日常主要活动场所,其每天在教室停留的时间长达5个多小时。教室中室内污染物含量的高低直接影响着学生学习和身体状况。因此,建筑设计时应综合考虑各方面因素,确定合理有效的通风方式,当采用机械通风方式时,新风量应不小于22~28 m3/h·人,化学、物理教室换气系数不应低于3次/h;采用自然通风方式时,夏热冬冷地区应优先采用外走廊设计。     

Experiences in radon-safe building in Finland

A study was made of radon-safe buildings in 300 Finnish low-rise residential buildings using data obtained from a questionnaire study. The study also aims at finding the main defects in design and implementation and how the guidance given on radon-safe buildings in slab-on-grade houses has been followed. According to the guidelines, the prevention of the flow of radon-bearing air from the soil into the house is recommended to be carried out through installation of aluminised bitumen felt and use of elastic sealants. Second, as a precaution perforated piping should be installed in the subsoil of the floor slab. The median indoor radon concentration in the houses was 155 Bq/m3. This is 32% lower than the median of the estimated reference values. The action level of 200 Bq/m3 was still exceeded in 40% of the houses. In most houses with slab-on-grade the prevention was based only on the installation of a sub-slab depressurisation system. Sealing was performed in a low number of houses. In 80% of houses with a sub-slab piping connected to an operating fan, radon concentration was below the action level of 200 Bq/m3. In houses with piping but no fan, the corresponding fraction was only 45%. Sub-slab piping without a fan had no remarkable effect on radon concentration. In houses with crawl-space and edge-thickened slabs, radon concentrations were low. The choice of foundation system thus significantly affects the indoor radon concentration. The importance of complete and careful sealing work should be stressed in advice and guides concerning radon prevention.     

Indoor radon concentrations caused by construction materials in 23 workplaces

The aim of this study was to compare the measured and the calculated concentrations of indoor radon caused by building materials at 23 workplaces. The measured concentrations of radon were clearly higher than the calculated radon concentrations from the building materials, which indicated that the main source of indoor radon was the soil under and around the buildings. The highest means of continuously (933 Bq m(-3)) and integrated (169 Bq m(-3)) measured and calculated (from 70 to 169 Bq m(-3)) concentrations of radon were found in hillside locations. On the other hand, the median (27 and 43 Bq m(-3)) and maximum (626 and 1002 Bq m(-3)) values of calculated indoor radon concentrations exhaled from construction materials were the highest at the ground level places. On average, only 7-19% of the radon seemed to originate from the construction materials.     

Correlations between radon concentration and indoor gamma dose rate, soil permeability and dwelling substructure and ventilation

Correlations between radon concentration and indoor gamma dose rate, soil permeability and dwelling substructure and ventilation were studied using data from 84 low rise residential houses collected in an area of enhanced indoor radon concentration. The radon concentrations varied from 30 to > 5000 Bq m(-3). Cross-tabulation, comparisons of means and multiplicative models were used to test the significance of the effects. In this study a quite high percentage of explained variation R2 (68%) was found. It was found that the most important factors were the substructure and the permeability of the soil. Due to the rather small sample size and moderate variation in the uranium content of the bedrock of the area, the effect of the indoor gamma dose rate was not so prominent. The effects of ventilation habits and sleeping with open windows were not detected in this study.     

Ventilation and radon transport in Dutch dwellings: computer modelling and field measurements

In 1995 and 1996 radon concentrations and effective air flows were measured in approximately 1500 Dutch dwellings built between 1985 and 1993. The goal of this investigation was to describe the trend in the average radon concentration by supplementing the first survey on dwellings built up to 1984 and to quantify the contributions of the most important sources of radon. In the living room of new dwellings the average radon concentration was 28 Bq m(-3), which is 50% higher than in dwellings built before 1970. Measurements of effective air flows showed the most important source of radon in the living room of new dwellings to be the building materials, with an average contribution of 70%. The other 30% comprised outside air and air from the crawl space in equal quantities. The long-term increase in the indoor radon concentration is mainly due to improvements in insulation since 1970, resulting in a fourfold decrease in infiltration through the building shell. Model calculations, supplementing the field measurements, confirmed the dominant effect of increasing airtightness of dwellings compared to effects of the observed trend in the use of building materials.     

Radon and Natural Ventilation in Newer Danish Single-Family Houses

Abstract To investigate the effect of ventilation on indoor radon (²²²Rn), simultaneous measurements of radon concentrations and air change rates were made in 117 Danish naturally ventilated slab-on-grade houses built during the period 1984–1989. Radon measurements (based on CR-39 alpha-track detectors) and air change rate measurements (based on the perfluorocarbon tracer technique; PFT) were in the ranges 12–620 Bq m^?3 and 0.16?0.96 h^?1, respectively. Estimates of radon entry rates on the basis of such time-averaged results are presented and the associated uncertainty is discussed. It was found that differences in radon concentrations from one house to another are primarily caused by differences in radon entry rates whereas differences in air change rates are much less important (accounting for only 80,0% of the house-to-house variation). In spite of the large house-to-house variability of radon entry rates it was demonstrated, however, that natural ventilation does have a significant effect on the indoor radon concentration. Most importantly, it was found that the group of houses with an air change rate above the required level of 0.5 h^?1 on average had an indoor radon concentration that was only 50% (0.5±0.1) of that of the group of houses with air change rates below 0.5 h^?1. The reducing effect of increased natural ventilation on the indoor radon concentration was found to be due mainly to dilution of indoor air. No effect could be seen regarding reduced radon entry rates.     

Indoor radon levels in selected hot spring hotels in Guangdong, China

Guangdong is one of the provinces that have most hot springs in China, and many hotels have been set up near hot springs, with spring water introduced into the bath inside each hotel room for hot spring bathing to attract tourists. In the present study, we measured radon in indoor and outdoor air, as well as in hot spring waters, in four hot spring hotels in Guangdong by using NR-667A (III) continuous radon detector. Radon concentrations ranged 53.4-292.5 Bq L(-1) in the hot spring water and 17.2-190.9 Bq m(-3) in outdoor air. Soil gas intrusion, indoor hot spring water use and inefficient ventilation all contributed to the elevated indoor radon levels in the hotel rooms. From the variation of radon levels in closed unoccupied hotel rooms, soil gas intrusion was found to be a very important source of indoor radon in hotel rooms with floors in contact with soils. When there was spring water bathing in the bathes, average radon levels were 10.9-813% higher in the hotel rooms and 13.8-489% higher in bathes compared to their corresponding average levels when there was no spring water use. Spring water use in the hotel rooms had radon transfer coefficients from 1.6x10(-4) to 5.0x10(-3). Radon in some hotel rooms maintained in concentrations much higher than guideline levels might thus have potential health risks to the hotel workers, and technical and management measures should be taken to lower their exposure of radon through inhalation.     

An empirical radon emanation model for residential premises

Based on an averaging technique, a methodology has been established to estimate an effective radon emanation factor M for residential premises. The model shows that the new term M and the ventilation rate are the essential parameters in estimating the level of indoor radon. M includes two components: the radon emanation rates of internal surface materials and the ratio of surface areas of applicable materials to premises volume. The value of M can be determined from on-site measurements. Different ventilation modes of a sampled residential unit during daytime and nighttime, with air conditioner on, window-open, and window-closed were included in site measurements. Each ventilation mode was measured twice during daytime and twice at night. During the investigation, air exchange rate, and indoor and outdoor radon levels were monitored simultaneously. The results of measurements were then used to verify the model. The value of M was found to be 31.7 Bq m⁻³ h⁻¹. The model is valid if the air exchange rate is larger than 0.2 h⁻¹.     

Investigations in Special “High Radon Areas” In Germany

The main source of high radon concentration indoors is the exhalation of radon from the soil. In the western part of Germany, two interesting regions, “Eifel” and “Hunsrück”, are selected for these radon investigations. The first region is an area with silt and sandstone of low uranium content but with tectonic fractures caused by postvolcanic activity, whereas in the part of the “Hunsrück” under consideration, the uranium concentration in the ground formerly allowed the extraction of uranium ores. An electrostatic deposit of the first radon daughter (Polonium-218-ion) onto a surface barrier detector and the subsequent analysis of the measured alpha spectra enables the determination of the concentration of radon in dwellings, its diffusion through and its exhalation rate from the soil. A maximum indoor concentration of radon of 8 kBq★m^?3 in a bedroom and approximately 35 kBq★m^?3 in a cellar room were determined in a house built in 1976. The daily variation between the minimum and the maximum concentration indoors amounts to a factor of ten. In these regions the radon concentration outdoors varies between 20 and 150 Bq★m^?3. The exhalation rates of radon from the soil are found to range from 0.002 to 1 Bq★m^?2★S^?1 The effects of sealing the ground slab with polyurethane and removing the air under the ground slab by suction will be presented.