PSI - Issue 22

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Author name / Structural Integrity Procedia 00 (2019) 000 – 000

António Curado et al. / Procedia Structural Integrity 22 (2019) 386–392 © 2019 The Authors. Published by Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the First International Symposium on Risk and Safety of Complex Structures and Components organizers

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Keywords: Radon risk assessment; radon remediation; radon risk mitigation; short-term monitoring

1. Introduction A traditional granite construction renovated over the last centuries, houses an administrative building with several offices, bureaus and help desks. The building retrofitting is the result of a series of annexations, renovations and additions, where the main refurbishment works took place by the end of the XIX century. The building is made of granite elements (walls, partitions and slabs) and its foundations are constructed on soils of granite and schist nature, quite prevalent in the geology of the North of Portugal. The administrative building located in an inner city in the North of Portugal was monitored in winter and summer 2018, in order to assess the risk of radon exposure, in a ground-floor office room extensively occupied. Additionally, it was monitored the indoor air temperature and relative humidity to check occupants´ thermal comfort. The radon risk analysis was based on data collected from short-term measurements, over a week, in the ground-floor office. The study included the manual register of all periods of office occupation. In short, the aim of this research is to study the effective radon risk in a ground-floor office occupied by 10 administrative employees working 7 hours a day, during a normal working week. In this risk analysis, the authors In order to study the effective radon risk, the author will use two different insights: the current Portuguese regulation towards radiological protection, in which is stipulated a so- called “reference level” regarding indoor radon concentration. This “reference level” must stay below 300 Bq.m -3 , and the insight advised by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), based on correct determination of Indoor Effective Dose (IED) on an annual basis, derived from radon exposure in indoor environments, according to WHO (2005) and WHO (2010). The compared analysis of both insights will be done by the authors in order to define which one is more suitable to implement a radon risk assessment for this ground-floor office. 2. The dosimetric analysis on radon evaluation The decomposition of the chemical element uranium, a metal found in deposits in granite massifs and rocks, leads to formation of the radon gas ( 222 Rn). Radon gas is radioactive and can be often detected in high concentrations in ground floor and basement levels. The accumulation of radon gas can be particularly harmful in buildings and indoor enclosures badly ventilated. The lack of ventilation in enclosed rooms will determine a radon concentration rise to a level that can negatively affect public health, cf. WHO (2005) and WHO (2010). Indeed, the aggregate effect of radon progeny and aerosol particles can increase notably the risk of lung cancer by inhalation. In the global ranking of lung cancer cause, WHO considers radon in buildings has the second major cause, immediately after tobacco smoking — WHO (2005) and WHO (2010). Due to its radioactive effect, the exposure to radon gas involves the absorption of a dose of radiation. The Radon concentration in the instrumented office was computed according to the metric presented. In (1) the referred metric is called ARC (Average Radon Concentration) and displayed in Bq.m -3 : defined the Office Occupation Schedule (OOC) according to:  11 months a year (mean value of working months a year)  4 weeks a month (mean value of working weeks a month)  5 days a week (mean value of working days a week)  7 hours a day (the occupancy period at the office a day)