Report and comprehensive database containing information to radon progeny activity concentration and aerosols characteristic in selected workplaces

The main objective of this report is to provide an overview of existing exposure to radon in underground workplaces. It constitutes deliverable 2.3 or Radonorm project which received funding from the Euratom research and training programme
2019-2020 under grant agreement No 900009.
The first part of the reports contains an exhaustive description of the specific conditions present in underground workplaces that determine exposure routes. Differences between outdoor situation or workplaces located in above ground buildings and specific role of radon decay product in the contribution to the effective dose received by workers was underlined. All processes and mechanisms leading to the specific exposure to radon as well as thoron progeny were defined and described in detail. Possible methods of exposure monitoring and dose evaluation were discussed. Hazard evaluation based on radon gas measurement have been compared with the one based on measurements of radon and thoron decay products measurements. A review of available measuring devices for radon gas as well for decay products, important from pragmatic perspective, was provided and roughly verified in terms of specific conditions present in an active mine. All pros and cons of described approaches were discussed in terms of physical as well as pragmatic terms of target use.
At the end of this part, a review of general approaches to the monitoring of radon hazard in many countries was included that were developed in frame of required Radon Action Plans. The general conclusion from this review is that radon hazard monitoring system based on radon progeny activity concentration (or potential alpha energy concentration - PAEC) is very rare. Majority of systems is established based on radon gas activity concentration monitoring and assumed country specific radon gas activity concentration reference levels. In very few cases radon progenies are considered when a reference level is exceeded.
The second part is focused on collecting more precise data about situation in underground mines. A database was developed for this purpose based on the information collected in the first part. The database records cover or detail the needed information for the evaluation of the radiation hazard based on radon gas activity concentration as well as decay products activity concentration or PAEC. The availability of data are limited due to the lack of such monitoring system in non-uranium mines. Where such data exist, the access is limited due to its confidential nature. The industries having such data are very hesitant to disseminate such information, due to ownership (data were gathered in frame of commercial contracts) and the fact that the problems of NORM and radon in workplaces is not often precisely regulated to date. Real examples based on available data in underground coal mines, as well as in zinc and lead mines were used for the discussion. A review of situations in some other mines based on more generic data is also included. Besides active mines, some examples of tourist mines and caves were presented. The general conclusion from the analysed features of specific underground workplaces is that the systems based on monitoring of radon progeny, or equilibrium factor for the final effective dose calculation, if exists, are using theoretical values of the effective dose per exposure, locally established, or based on ICRP recommendation. Aerosols characteristics, especially radioactive ones, are rarely used for the definition of site-specific values of the effective dose per exposure, mainly due to the lack of appropriate measuring equipment (applicable in mines) as well as the lack of driving force mobilising to more accurate effective dose evaluation.
For pragmatic purposes as well as for an educational one a specific software was developed facilitating the understanding of radon hazard features under specific conditions present in underground workplaces. The Ventgraph system, developed in WP 5.4, is also presented, as a tool for simulation of radon and radon progeny distribution in a mine with mechanical ventilation. It can be used for developing either monitoring or mitigation of radon hazard as well as for educational purposes to know importance of main parameters determining radon hazard in an active mine.

本报告的主要目标是全面概述地下工作场所当前的氡（radon）暴露现状。本报告属于Radonorm项目的交付成果2.3，该项目获欧洲原子能共同体（Euratom）2019-2020年研究与培训计划资助，资助协议编号为900009。

报告第一部分详尽阐述了决定暴露途径的地下工作场所特定环境条件，明确区分了户外场景、地上建筑内工作场所与地下场景的差异，并着重强调了氡衰变子体在工作人员有效剂量贡献中的特殊作用。本部分详细定义并阐释了导致氡及钍射气（thoron）子体特异性暴露的全部过程与机制，探讨了暴露监测与剂量评估的可行方法，对比了基于氡气测量的危害评估与基于氡及钍射气衰变子体测量的危害评估结果。此外，本部分从实用视角出发，梳理了适用于氡气及衰变子体检测的现有测量设备，并结合活跃矿井的特定环境条件对其进行了初步验证，从物理特性与目标应用的实用维度，分析了上述各类方法的优劣。

本部分末尾，梳理了多国依据强制氡行动方案制定的氡危害通用监测方法。该梳理得出的总体结论为：基于氡衰变子体活度浓度（或潜在α能量浓度（PAEC））的氡危害监测系统极为稀缺。绝大多数监测系统均基于氡气活度浓度监测建立，并采用各国自行制定的氡气活度浓度参考限值。仅在极少数场景中，当氡气活度浓度超出参考限值时，才会考量氡衰变子体的影响。

报告第二部分聚焦于收集地下矿井的精准现场数据。基于第一部分收集的信息，本部分构建了专用数据库。该数据库收录并细化了基于氡气活度浓度、衰变子体活度浓度或潜在α能量浓度（PAEC）开展辐射危害评估所需的全部必要信息。由于非铀矿井普遍缺乏此类监测系统，相关数据的可获取性极为有限；即便存在此类数据，因其属于涉密信息，访问权限也受到严格限制。掌握此类数据的企业因数据所有权（相关数据系依据商业合同收集）以及当前工作场所天然放射性物质（Naturally Occurring Radioactive Materials）与氡问题尚未得到精准规范的现状，普遍不愿公开相关信息。本部分结合地下煤矿、锌矿及铅矿的现有实际数据展开讨论，并基于通用数据梳理了其他部分矿井的现场情况。除活跃矿井外，本部分还展示了旅游矿井与洞穴的相关案例。通过对地下工作场所特定特征的分析，本部分得出总体结论：若存在基于氡衰变子体监测或平衡因子计算最终有效剂量的系统，其要么采用当地制定的单位暴露有效剂量理论值，要么依据国际辐射防护委员会（International Commission on Radiological Protection，简称ICRP）的推荐标准。气溶胶特性（尤其是放射性气溶胶）极少用于定义单位暴露有效剂量的场地特异性数值，这主要是因为缺乏适用于矿井环境的专用测量设备，且缺乏推动开展更精准有效剂量评估的动力。

为满足实用与教育需求，本报告开发了一款专用软件，用于帮助理解地下工作场所特定环境下的氡危害特征。此外，本报告还介绍了在WP 5.4中开发的Ventgraph系统，该系统可模拟机械通风矿井内氡及氡衰变子体的分布情况，既可用于开发氡危害监测与缓解方案，也可用于教学演示，帮助理解活跃矿井中决定氡危害的核心参数的重要性。