住宅内和工作场所中氡－222的防护

本文介绍住宅内和工作场所中氡的防护原则，论及了ＩＣＲＰ有关住宅内和工作场所中氡防护问题的若干建议，并简述降低建筑物内氡及其子体浓度的实用途径。最后，通过住宅内和工作场所中氡浓度现状举例提示氡的防护问题的重要性。     

隧道施工场所的氡浓度调查及防护建议

目的 调查隧道施工场所空气氡浓度水平。方法 采用PCMR-2连续测氡仪,在4个施工隧道作业场所进行空气氡浓度检测。结果 4个施工主洞最小氡浓度分别达到897Bq/m³、589Bq/m³、527Bq/m³和788Bq/m³,最大氡浓度分别到达2087Bq/m³、3764Bq/m³、2223Bq/m³和2480Bq/m³,介于工作场所氡浓度补救行动水平上限的2.1~3.7倍之间。结论 在隧道工作场所氡浓度水平可能超出国家相关标准,隧道施工人员的氡防护问题应该受到关注和重视。     

室内氡的水平与控制措施

目的 验证北京市室内氡水平的分布,提出控制室内氡浓度若干途径。方法 以清华大学工程物理系室内环境质量评价中心测量的室内氡浓度数据与中国疾病预防与控制中心辐射防护核安全医学所、北京东城区卫生防疫站环卫科等单位在北京的测量数据相互印证,分析了北京市室内氡浓度的大致范围。结果 上述三家单位的氡浓度测量数据一致性比较好。结论 我国制定的"室内氡浓度行动水平"与发达国家制定的标准基本相同。在国家综合实力许可的情况下,应降低干预室内氡的行动水平,把氡致肺癌危险度降到最优化水平。加强通风、降低氡的析出率和建材控制等是室内氡的水平的有效控制措施。     

住宅内和工作场氘中氡——222的防护

本文介绍住宅内和工作场所中氡的防护原则，论及ＩＣＲＰ有关住宅内和工作我中秘书科防护问题的若干建议，并简述降低建筑物内氡及其子体浓度的实用途径。最后，通过住宅内和工作场所中氡浓度现状举例提示氡的防护问题的重要性。     

雅安市水电地下工作场所放射性水平调查

目的调查雅安市水电地下工作场所放射性水平。方法采用直读式仪器与ATD固体径迹法测量空气氡浓度和γ射线剂量率。结果雅安市7个水电地下场所共监测30个作业点,平衡当量氡浓度水平在5.0~364.8 Bq/m3范围,γ剂量率在28.6~236.4μSv/h范围,符合《地下建筑氡及其子体控制标准》(GBZ 116-2002)等标准要求。结论所测点空气氡浓度符合标准要求,通风是降低氡浓度水平的有效措施。     

上海地下公共空间环境氡浓度调查

[目的]选择典型地铁站站台、地下商城(商业街)和地下停车库,对氡浓度现状进行调查与评价,为地下公共空间环境管理提供科学依据。[方法]地下场所空气氡浓度测定采用电子测氡仪(RAD-7)测定空气中的222Rn浓度来实施。[结果]①4个检测地铁站站台中,上海新客站站台的氡浓度水平较低,中山公园站其次,人民广场站和宜山路站较高;②4个检测点中,上海新客站和科技馆站地下商城/商业街的氡浓度水平较低,人民广场站和徐家汇站次之;③上海新客站和上海虹桥站地下停车库的氡浓度较低,而上海浦东国际机场地下车库次之,两者相差达6～10倍。[结论]同一类型地下场所空气氡浓度对比表明,三城市中,上海地下场所/商业街空气氡浓度最低;4城市中,上海地铁站站台空气氡浓度居中;上海地下停车库空气氡浓度低于我国部分城市均值。不同类型地下场所空气氡浓度对比表明,上海地下停车库低于地下商城/商业街,地下商城/商业街低于地铁站站台;上海地下场所空气氡浓度水平高于地面建筑物室内,远低于全国地下室,低于国家职业卫生控制标准。     

新疆某露天煤矿放射性水平调查及人员受照剂量评价

目的 对新疆某开采多年的伴生放射性大型露天煤矿的各场所γ剂量率水平和氡浓度水平进行调查和分析;并评价从业人员所受有效剂量。方法 采用便携式γ剂量率仪FH40G对矿区进行定点监测,利用连续测氡仪对场所内氡浓度水平进行24 h连续监测;并根据测量的γ剂量率和氡浓度估算人员受照剂量。结果 该露天煤矿γ剂量率范围为51.4～435.8 nGy/h,氡浓度24 h平均值为15～25 Bq/m³,人员年有效剂量范围为0.29～1.29 mSv/a。结论 各场所氡浓度水平较低,不需要采取补救行动;大部分场所人员受照剂量远远低于标准要求,排土场局部地区需要采取一定的防护措施。     

我国锡矿山的辐射水平和放射卫生防护对策研究

目的 探索辐射水平在我国锡矿山的分布情况,在此基础上提出放射卫生防护的建议,为保护锡矿山井下工人身体健康提供科学依据。方法 分析、应用文献资料和现场调查的测量结果,得到了锡矿山井下工作场所的辐射水平。结果 锡矿山井下环境中γ辐射空气吸收剂量率绝大部份属于正常本底辐射水平。早期,锡矿山井下工作场所空气中氡浓度及氡子体α潜能浓度浓典型值分别为3.12 kBq/m³和5.61μJ/m³。目前,绝大多数锡矿山井下工作场所空气中氡浓度及氡子体α潜能浓度,分别低于1 000 Bq/m³和3.57μJ/m³。结论 锡矿山工作人员中凡个人年有效剂量大于1mSv或物料中天然铀比活度大于1 Bq/g的锡矿山均应进行放射卫生防护的审管。锡矿山井下工作场所空气中氡及氡子体α潜能浓度和井下环境中γ辐射空气吸收剂量率管理限值分别为1 000 Bq/m³、3.57μJ/m³和1μGy/h。锡矿山井下矿工个人剂量管理目标值定为10mSv/a。工作人员总的年有效剂量超过10 mSv时,工作人员应视为放射工作人员。     

云南省某矿区氡浓度水平调查分析

目的 调查云南省某锡矿、铜矿及非矿区居室内空气中的氡浓度以及相应采样点自来水中氡浓度，估算人体受照剂量。方法 径迹法测量锡矿、铜矿井下、地上工作场所空气中的氡浓度，使用RAD7仪器连续测量法测得居室内空气中氡浓度、RAD7水氡测量系统测量自来水氡浓度。评估不同来源氡所致受照剂量的贡献。结果 锡矿的矿下、地上工作场所空气平均氡浓度分别为（7 473 ±3 105）Bq·m⁻³和（332 ±238）Bq·m⁻³，其所致年剂量贡献分别为（29.44 ±12.23）mSv和（2.50 ±1.79）mSv；铜矿井下、地上工作场所空气中氡浓度分别为（4 477 ±5 152）Bq·m⁻³和（110 ±32）Bq·m⁻³，其所致年剂量贡献分别为（17.64 ±20.30）mSv和（0.83 ±0.24）mSv；居室空气氡浓度（76 ±33）Bq·m⁻³及年剂量贡献（2.01 ±0.87）mSv。铜矿及锡矿的自来水氡浓度测量结果分别为（1.66 ±2.00）Bq·L⁻¹和（3.94 ±1.81）Bq·L⁻¹，高于市内32个采样点自来水氡浓度（0.39 ±0.21）Bq·L⁻¹。结论 目前所测区域水氡所致剂量贡献相对较小，锡矿、铜矿区井下工作场所空气氡浓度值得关注，应重视对矿工使用防护用具的宣传教育工作。     

某铀矿10年监测资料分析和井下氡及其子体浓度的分布

目的了解某铀矿井下氡及其子体在10年间不同年份、不同季节、不同场所的分布规律,以便有针对性地采取井下降氡措施。方法收集1995~2004年间某铀矿井下氡及其子体浓度资料,计算平衡当量氡浓度及平衡因子F。结果主要工作面(一类)的氡及其子体浓度均高于辅助工作面(二类)(P<0.01),未通风时的氡浓度明显高于通风时的浓度(P<0.01)。铀矿井下氡及其子体浓度在夏季、秋季比春季、冬季高,5月和9月的水平接近年平均水平。在出碴、出矿、打钻和支柱等主要作业面的作业点处氡及其子体浓度较高。导出铀矿井下空气中年平均氡浓度为2 977 Bq/m3,测定样品中超过年平均浓度的占26%,平均平衡因子F=0.34。结论通风是降低井下氡及其子体浓度主要的有效方法。5月和9月是调查铀矿井下氡及其子体平均辐射水平可考虑的最佳季节。     

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.     

Current status of programmes to measure and reduce radon exposure in Irish workplaces.

National legislation, which implements European Council Directive 96/29/EURATOM in Ireland, sets a reference level of 400 Bq m(-3) averaged over any 3 month period for radon exposure in the workplace and also empowers the Radiological Protection Institute of Ireland to direct employers to have radon measurements carried out. This legislation came into effect in May 2000. Radon measurements have already been completed in show caves and other underground workplaces. Between 1998 and 2001, over 33 800 individual radon measurements were carried out in all ground floor offices and classrooms in 3444 schools nationwide as part of a programme undertaken jointly with the Department of Education and Science. Where the average indoor radon concentration in one or more rooms exceeded 200 Bq m(-3), remedial measures were implemented. For concentrations up to 400 Bq m(-3) this involved increased ventilation while for higher concentrations an active sump was normally installed. The results of the survey, as well as the effectiveness of the different remedial strategies, are discussed. In the case of other above ground workplaces, different approaches have been adopted. As a first step, workplaces in two known high radon areas were directed to have radon measurements carried out. This programme had limited success because of problems in obtaining accurate workplace databases and a general lack of awareness on the part of employers of the issues involved. From a sample of 2610 employers directed to measure radon, only 408 actually completed measurements and 37 workplaces were identified as having average 3 month average radon concentrations above 400 Bq m(-3). A total of 1356 employers ignored all correspondence, some of which was sent by registered post and signed for on receipt. Current initiatives are focused on the provision of information and include newspaper advertising as well as publications aimed specifically at both employer and employee representative groups. The ability to provide accurate information that encourages both measurement and remediation is seen as central to an effective radon workplace programme.     

The concept of equivalent radon concentration for practical consideration of indoor exposure to thoron

To consider the total exposure to indoor radon and thoron, a concept of equivalent radon concentration for thoron is introduced, defined as the radon concentration that delivers the same annual effective dose as that resulting from the thoron concentration. The total indoor exposure to radon and thoron is then the sum of the radon concentration and the equivalent radon concentration for thoron. The total exposure should be compared to the radon guideline value, and if it exceeds the guideline value, appropriate remedial action is required. With this concept, a separate guideline for indoor thoron exposure is not necessary. For homes already tested for radon with radon detectors, Health Canada's recommendation of a 3-month radon test performed during the fall/winter heating season not only ensures a conservative estimate of the annual average radon concentration but also covers well any potentially missing contribution from thoron exposure. In addition, because the thoron concentration is much lower than the radon concentration in most homes in Canada, there is no real need to re-test homes for thoron.     

Radon—A regional electricity company approach to assessment and control

There are statutory limits on exposure to radon in workplaces in the United Kingdom [Health and Safety, The Ionizing Radiation Regulations, Statutory Instrument 1333. HMSO, London (1985)]. South Western Electricity plc (SWEB) employs approximately 5500 staff within the group in the area which stretches from the Isles of Scilly to Bristol and across into South Wales and Southern England (where it has retail outlets) in parts of which high concentrations of radon can be expected [Radiation doses—maps and magnitudes. NRPB, Didcot (1985)]. The Company's method of assessment and details of a successful remediation scheme installed in a large modern office are described.     

Radon action level for high-rise buildings

Radon and its progeny are the major contributors to the natural radiation dose received by human beings. Many countries and radiological authorities have recommended radon action levels to limit the indoor radon concentrations and, hence, the annual doses to the general public. Since the sources of indoor radon and the methods for reducing its concentration are different for different types of buildings, social and economic factors have to be considered when setting the action level. But so far no action levels are specifically recommended for cities that have dwellings and offices all housed in high-rise buildings. In this study, an optimization approach was used to determine an action level for high-rise buildings based on data obtained through previous territory-wide radon surveys. A protection cost of HK$0.044 per unit fresh air change rate per unit volume and a detriment cost of HK$120,000 per person-Sv were used, which gave a minimum total cost at an action level of 200 Bq m(-3). The optimization analyses were repeated for different simulated radon distributions and living environment, which resulted in quite significantly different action levels. Finally, an action level of 200 Bq m(-3) was recommended for existing buildings and 150 Bq m(-3) for newly built buildings.     

Do the UK workplace Radon Action Levels reflect the radiation dose received by the occupants?

In the UK, Action Levels for radon have been established at 400 Bq m(-3) for the workplace and 200 Bq m(-3) for the home. We have estimated the dose received by occupants of rooms with radon levels near or above the Action Level, using hourly radon readings, and a questionnaire to record occupancy. In the workplace, results for 73 staff suggest that doses are lower than expected, partly due to part-time working and partly due to the mobility of staff. The 75% quantile for the series, corrected to a 37 hour week, is 5.2 mSv at 400 Bq m(-3). Compared to the current annual limit for radiation workers, the Action Level could be increased, but the current Action Level is compatible with the recent EEC Directive requiring a lower dose limit. However, when raised radon levels in the workplace were reduced by remediation in the series we studied, the dose reduction to staff was consistently around half of the radon level reduction. Although it would be appropriate to study more locations, this suggests an Action Level for remediated workplaces of 200 Bq m(-3). Finally, in a limited series of dose assessments in domestic properties, we found that doses could considerably exceed 5 mSv at the 200 Bq m(-3) Action Level, primarily because the sample included an example of high occupancy, in our case several Asian wives in purdah, whose occupancy was almost total.