Contribution from thoron on the response of passive radon detectors

In order to evaluate the reliability of measured values of radon concentration, a thoron sensitivity test for passive radon detectors was carried out. To do this test, a thoron chamber system was first set up. The system consists of four parts: an exposure chamber, a gas generator, an environmental monitor, and a measuring device. Five types of radon detectors were examined using the chamber system. After connecting the exposure chamber with the gas generator through an external pump, thoron gas was circulated through the system. The detectors were exposed to thoron-rich air for several days. The mean ratio between thoron and radon concentrations throughout the exposure period was 10:1. Some of the detectors provided values different from the actual radon concentration. Although the presence of thoron can be negligible in most cases, it is necessary to check the thoron contribution to the detector response with the proposed or similar test before practical use.     

Application of pylon radon daughter standard for calibration of radiometers

Radiometers for measurements of radon daughter potential energy used in the surveillance of the work environment need a systematic calibration. This paper presents how a commercially available device produced by the Pylon Company can be applied. This device allows to produce, simply and directly, standard sources of radon daughters, corresponding with the energy, geometry and properties of radiation originated from an air sample. The calibration yielded the results that proved to be in agreement with those obtained previously by means of radon chamber.     

Passive, integrated measurement of indoor radon using activated carbon

Activated carbon canisters were tested to determine their adsorption and retention characteristics for radon. Our tests conducted indoors under typical conditions of temperature and relative humidity indicate that simple, inexpensive and maintenance-free passive devices containing 150-200 g of activated carbon can measure radon conveniently and adequately. The amount of radon absorbed in the collector is determined by counting the gamma rays from the decay products of radon. The lower limit of detection for radon is 0.2 pCi/l. for an exposure of 72 hr. Greater sensitivity can be obtained with larger counting systems and devices containing carbon with more surface area. Tests in a residential building and in a test chamber indicate that the measured radon in the canister is proportional to the mean concentration of radon during the period of exposure when correction for relative humidity is made. For practical situations encountered indoors, the device yields results accurate to within +/- 20%. Results from field measurements indicate that the use of the device is feasible.     

大气压强对介质表面氡析出率的影响

目的 了解介质表面氡析出率在1天中受大气压强变化的影响。方法 利用双室开环平衡法测量氡析出率,在氡析出率参考标准装置上,测量1天中每30分钟氡析出率的数值,绘制氡析出率在1天中的变化曲线,与大气压强在1天中的变化规律作比较,分析介质表面氡析出率受大气压强的影响。结果 被测介质表面氡析出率测量值在1天中随气压的变化在（1.591 2~1.950 9）Bq·m^-2·s^-1之间波动;氡析出率的高值出现在气压低值范围内。结论 介质表面氡析出率值随大气压强降低而明显升高,但压强升高时,氡析出率值降低不明显。     

Indoor radon and well water radon in Virginia and Maryland

The domestic use of radioactive water has long been a cause for concern, but only a few studies have examined prolonged exposure to radionuclide concentrations found in natural settings. This paper reports on the indoor radon concentrations from 1,500 homes in northern Virginia and southern Maryland and well water radon from 700 homes in the same area. Indoor radon concentrations are almost all between 1 and about 40 pCi/L. The winter season shows the highest values with about 40% of the homes over the US EPA action level of 4.0 pCi/L. The summer season shows the lowest values with about 25% of the homes over this level. This seasonal variation is related to home ventilation. Waterborne radon in homes with private well ranges from about 100 pCi/L to about 8,000 pCi/L. In small homes, indoor radon can be significantly increased by outgassing of the home water supply, even at water radon levels of less than 10,000 pCi/L.     

Optimistic biases in public perceptions of the risk from radon.

Survey data were obtained from a random sample of 657 homeowners in New Jersey and also from 141 homeowners who had already monitored their homes for radon. People who had not tested tended to believe that they were less at risk than their neighbors, and they interpreted ambiguous predictors of home radon levels in ways that supported their beliefs of below-average risk. Residents who had already tested their homes were relatively accurate about the probability of health effects. In both groups less than half of those who knew that radon can cause lung cancer were willing to admit that it would be serious if they suffered health effects from this source. The optimistic biases of the public may hamper attempts to encourage home radon monitoring and to promote appropriate mitigation measures in homes with elevated radon concentrations.     

Spatial and temporal indoor radon variations.

This paper examines the ability of standard radon measurement protocols to predict long-term radon concentrations in houses located in the upper Midwest. It was observed that: (1) significant radon variations can occur on a spatial scale as small as a single floor; (2) radon measurements that integrate for periods less than 3 mo are reliable only to within a factor of 2 or more; and (3) contemporary, short-term measurements within existing structures may not accurately reflect past radon concentrations. Two-hundred forty-three occupied houses located in 40 towns were monitored for at least 1 y using alpha-track detectors. If lifetime radon exposure estimates need to be determined accurately, then long-term, integrating radon detectors should be placed in several rooms of each house. In radon atmospheres that may not be stable for long periods of time, it is suggested that multiple, year-long measurements or surface alpha activity measurements in combination with year-long alpha-track measurements are needed for an accurate lifetime radon assessment.     

Dynamic adsorption of radon by activated carbon

The adsorption of radon on activated carbon has been used in or considered for a number of applications, including in situ decay beds, cyclic decontamination systems, and diffusive samplers. And although there are numerous measurements of the adsorption coefficients of specific activated carbons for radon, each of these applications depends on knowing, in addition to the adsorption coefficient for radon, the mass transfer factors describing its dynamic adsorption. Here we used a standard procedure in gas chromatography and chemical engineering, the spreading of a pulse as it passes through a bed of adsorbent, to determine these mass transfer factors. For this application, this procedure is developed further to correct the radon adsorption data for distortions caused by the decay of radon and by the presence of radon decay products in the detector. The results from eight activated carbons show a wide variation in the mass transfer coefficients for radon, which could affect significantly the suitability of adsorbents, as demonstrated here by the effect that mass transfer has on the performance of in situ decay beds.     

Investigation of atmospheric, mechanical and other pressure effects influencing the levels of radon and radon progeny in buildings.

Real-time data measurement and analysis have identified a number of influences affecting the variability and accumulation of radon and its progeny in indoor air. Observed cycles in radon concentrations were shown to be related to the influence of air-conditioning and water-heated central heating systems. The cyclical pattern, related to operation of the air-condition system, showed radon levels almost four times lower during the period when the system was switched On than when it was Off. When the heating system was switched On the radon and radon progeny levels were 40% lower than when it was switched Off. Under both regimes, it was possible to establish the over-riding influence of meteorological factors by separating the recurring cyclical component from the relevant data set. The general or trend level of indoor radon was determined substantially by the prevailing atmospheric conditions.     

Occupational doses from radon in Spanish spas

Recent international recommendations have included exposure to natural radiation as one of the sources to monitor in certain occupationally exposed groups. Among those mentioned are workers in thermal spas, who may be exposed to high radiation doses due to the high concentration of radon in the indoor air of the spa. This paper presents the methodology and the results of an evaluation of radiation doses to the staff in different thermal spas in Spain. Different series of samples were collected and measurements made for the radon concentrations in water in 54 spas and in air in 20 spas. In six of the latter group, the air radon concentration was studied in different working areas occupied by the employees. The radon concentrations in water were between <2 and 775 x 10(3) Bq m(-3). The radon concentrations in air were between <10 and 5,200 Bq m(-3). The latter were used to estimate the dose received by each occupational group in the spa by taking into account the radon concentration in their main working area. By means of an exposure-dose conversion factor of 1.43 Sv per J h m(-3), the estimated effective doses were found to lie between 1 and 44 mSv y(-1). This upper limit is higher than the recommended annual limit of 20 mSv y(-1) for an occupational dose.     

Effect of sorption barriers on the radon fluence rate from soil.

The fluence rate of radon from soil as affected by active sorption barriers [activated carbon (AC) and mordenite], soil moisture content, and temperature was measured over a period of 964 d. (To limit the level of radon in indoor environments, an active sorption barrier potentially could be mixed with soil placed adjacent to the substructures of buildings.) AC, mixed with the top layer of soil in columns, markedly reduced the fluence rate of radon from soil over the entire time of the experiment and at all moisture contents and temperatures examined. Mordenite, on the other hand, was not effective in decreasing the fluence rate. AC also has a relatively high sorption capacity for aqueous lead species. (Stable lead isotopes are end-products in the uranium and thorium decay series of which radon isotopes are members.) Thus, the long-term (decades) efficacy of AC in sorbing radon in a soil environment will not be compromised by the blocking of its sorption sites by lead.     

Site characterization for radon supply potential: a progress review.

"Radon-resistant" house foundations were developed by 1981, but additional construction costs made it undesirable to require them unless necessary. The survey methods used then were labor-intensive and cost so much that it was impractical to identify "radon-prone" areas by nationwide surveys. A cheaper method was required to show where radon-resistant foundations were needed. Information available in 1981 suggested that unusual soil conditions were needed to produce high radon concentrations in houses. If these conditions could be identified, elevated radon concentration levels could be predicted from soil measurements at a lower cost than a radon-in-housing survey. Recent radon surveys show that near-surface bedrock or clay soils, which cover most of the continent, are radon-prone. The measurement methods cannot be used in these soils. The cost of radon surveys has been greatly reduced over the past 10 y. Radon-prone areas can now be identified by radon surveys at a lower cost than soil measurements, and the cost of radon-resistant foundations has been reduced. These developments have removed most of the financial incentive for developing soil-based site classification methods. The priority task now is to encourage the adoption of radon-resistant foundations in radon-prone areas.     

Doses to organs and tissues from radon and its decay products.

This paper discusses the doses from radon and from its short-lived decay products to a number of organs and tissues and to the foetus. The aim is to put all these doses into context rather than concentrating only on the largest contributions. There is also a brief discussion of the evidence from epidemiology on the risks of exposure to radon and its decay products. As is well known, under normal circumstances the greatest hazard is to the respiratory tract from inhalation of radon decay products. Radon decay products may also give substantial doses to skin. Under some circumstances it seems likely that ingested radon could give significant doses to the stomach. Other risks appear to be smaller; the results given here allow them to be compared.     

降氡方法在室内氡污染治理中的应用与分析

目的 探索降低住宅氡及其子体浓度水平的合适方法.方法 选取3个房间分别采取自然通风、空气净化器、密封屏蔽的措施后,使用EQF3120型氡及其子体测量仪测量室内氡及其子体浓度,α核径迹探测器测量室内氡浓度,并比较不同方法的降氡效果.结果 自然通风2～10 h后,房间内氡、结合态氡子体和未结合态氡子体浓度平均降低率分别为8...     

Mapping variation in radon potential both between and within geological units.

Previously, the potential for high radon levels in UK houses has been mapped either on the basis of grouping the results of radon measurements in houses by grid squares or by geological units. In both cases, lognormal modelling of the distribution of radon concentrations was applied to allow the estimated proportion of houses above the UK radon Action Level (AL, 200 Bq m(-3)) to be mapped. This paper describes a method of combining the grid square and geological mapping methods to give more accurate maps than either method can provide separately. The land area is first divided up using a combination of bedrock and superficial geological characteristics derived from digital geological map data. Each different combination of geological characteristics may appear at the land surface in many discontinuous locations across the country. HPA has a database of over 430,000 houses in which long-term measurements of radon concentration have been made, and whose locations are accurately known. Each of these measurements is allocated to the appropriate bedrock--superficial geological combination underlying it. Taking each geological combination in turn, the spatial variation of radon potential is mapped, treating the combination as if it were continuous over the land area. All of the maps of radon potential within different geological combinations are then combined to produce a map of variation in radon potential over the whole land surface.     

High radon exposure in a Brazilian underground coal mine.

The main source of radiation exposure in most underground mining operations is radon and radon decay products. The situation of radon exposure in underground mining in Brazil is still unknown, since there has been no national regulation regarding this exposure. A preliminary radiological survey in nonuranium mines in Brazil indicated that an underground coal mine in the south of Brazil had high radon concentration and needed to be better evaluated. This paper intends to present an assessment of radon and radon decay product exposure in the underground environment of this coal mining industry and to estimate the annual exposure to the workers. As a product of this assessment, it was found that average radon concentrations at all sampling campaign and excavation sites were above the action level range for workplaces of 500-1500 Bq m(-3) recommended by the International Commission on Radiological Protection--ICRP 65. The average effective dose estimated for the workers was almost 30 times higher than the world average dose for coal miners.     

Diffusive sampling of radon

Information required for the design and testing of diffusive samplers for radon is scattered across numerous disciplines, making it difficult to use. To aid future research, a multidisciplinary review is given addressing the following: 1) the differential equations describing mass transfer in a radon diffusive sampler; 2) mathematical procedures for solving these equations; 3) the physical parameters defining the adsorbent in the diffusive sampler; and 4) a standardized protocol for validating the performance of diffusive samplers for radon.     

Exposure to atmospheric radon.

We measured radon (222Rn) concentrations in Iowa and Minnesota and found that unusually high annual average radon concentrations occur outdoors in portions of central North America. In some areas, outdoor concentrations exceed the national average indoor radon concentration. The general spatial patterns of outdoor radon and indoor radon are similar to the spatial distribution of radon progeny in the soil. Outdoor radon exposure in this region can be a substantial fraction of an individual's total radon exposure and is highly variable across the population. Estimated lifetime effective dose equivalents for the women participants in a radon-related lung cancer study varied by a factor of two at the median dose, 8 mSv, and ranged up to 60 mSv (6 rem). Failure to include these doses can reduce the statistical power of epidemiologic studies that examine the lung cancer risk associated with residential radon exposure.     

EQF3120氡及其子体测量仪及应用

目的对EQF3120氡及其子体测量仪的测量效果进行验证和比较,以了解仪器性能与测量效果。方法仪器的校准在标准氡室进行,比对和应用选择典型房间,采用同类型仪器进行现场测量。结果在标准氡室选择的高、低氡（CRn）和氡子体潜能浓度（Cp）EQF3120对两者的校准系数分别为1.16,1.13和0.97,0.95;现场比对结果的比率在1.10,1.12和0.95,1.07。结论本测试结果表明,EQF3120氡及其子体测量仪可同时测量CRn、CpRn和CpRnDu等多项指标,所得结果与国内外同类探测器有较好的可比性。     

某铀矿退役治理工程竣工五年后氡析出率调查

目的 对广西某铀矿采冶退役治理工程竣工五年后有限制开放区域的氡析出率水平进行研究分析，评价潜在环境危害因素和安全隐患，为矿区今后长期监护提供科学依据。方法 对治理后达到有限制开放区域按网格布点法布设150个测点，利用氡测量仪器开展氡析出率测量，并对结果进行统计分析。结果 发现部分监测点位的氡析出率水平高于退役治理工程竣工环境保护验收监测时的水平，这些点位氡析出率水平的增高与边坡的位移、风蚀雨刷所致覆盖层有裂隙、厚度减少有关。结论 实施铀矿采冶工程退役后长期监护工作是极其重要的。