Uncertainties in the evaluation of the dose coming from radon in tourist caves (original) (raw)
Related papers
Journal of Hazardous Materials, 2007
High concentrations of radon exist in several workplaces like tourist caves mainly because of the low ventilation rates existing at these enclosures. In this sense, in its 1990 publication, the ICRP recommended that high exposures of radon in workplaces should be considered as occupational exposure. In developed caves in which guides provide tours for the general public great care is needed for taking remedial actions concerning radon, because in some circumstances forced ventilation may alter the humidity inside the cave affecting some of the formations or paintings that attract tourists. Tourist guides can work about 1900 h per year, so the only option to protect them and other cave workers from radon exposure is to apply an appropriate system of radiation protection mainly based on limitation of exposure by restricting the amount of time spent in the cave. Because of the typical environmental conditions inside the caves, the application of these protecting actions requires to know some indoor air characteristics like particle concentration, as well as radon progeny behaviour in order to get more realistic effective dose values In this work the results of the first two set of radon measurements program carried out in 10 caves located in the region of Cantabria (Spain) are presented. 9 10 11 12 13 14 15 16 17
Radon continuous monitoring in Altamira Cave (northern Spain) to assess user's annual effective dose
Journal of Environmental Radioactivity, 2005
In this work, we present the values of radon concentration, measured by continuous monitoring during a complete annual cycle in the Polychromes Hall of Altamira Cave in order to undertake more precise calculations of annual effective dose for guides and visitors in tourist caves. The 222Rn levels monitored inside the cave ranges from 186 Bq m−3 to 7120 Bq m−3, with an annual average of 3562 Bq m−3. In order to more accurately estimate effective dose we use three scenarios with different equilibrium factors (F=0.5F=0.5, 0.7 and 1.0) together with different dose conversion factors proposed in the literature. Neither effective dose exceeds international recommendations. Moreover, with an automatic radon monitoring system the time remaining to reach the maximum annual dose recommended could be automatically updated.
2015
Copyright © 2015 by Hirosaki University. All rights reserved. The regulation of radiation exposure originating from radon has become strict during the past years; in 2014 the reference level was given to be 300 Bq/m3 in case of dwellings and other buildings with high occupancy factor by International Basic Safety Standards (IAEA BSS) – released by IAEA – or the maximum allowable value in non-radiation conditions (radiation workers)1). We had previously been surveying the changes of radon concentration in the tourist caveʼs air for 8 years, and had measured the radiation exposure of those working there for 11 years. The 8-year average of radon concentration was 7430 Bq/m3. Before the renovation works at the end of 2011 (removing previous coal slag filling) it was 8630 Bq/m3, while during the years 2012-2014 it was 5430 Bq/m3, however, it still considerably exceeds the current reference level of 1000 Bq/m3 (and that planned for the future as 300 Bq/m3). The workersʼ radiation exposure...
Radon levels in Romanian caves: an occupational exposure survey
Environmental Geochemistry and Health, 2016
A comprehensive radon survey has been carried out in seven caves located in the western half of Romania's most significant karst regions. Touristic and non-touristic caves were investigated with the aim to provide a reliable distribution of their radon levels and evaluate the occupational exposure and associated effective doses. Radon gas concentrations were measured with long-term diffusion-type detectors during two consecutive seasons (warm and cold). All investigated caves exceed the European Union reference level of radon gas at workplaces (300 Bq/m 3). The radon concentration in these caves ranges between 53 and 2866 Bq/m 3 , reflecting particular cave topography, season-related cave ventilation, and complex tectonic and geological settings surrounding each location. Relatively homogeneous high radon levels occur in all investigated touristic caves and in Tȃuşoare and Vântului along their main galleries. Except for Muierii, in all the other caves radon levels are higher during the warm season, compared to the cold one. This suggests that natural cave ventilation largely controls the underground accumulation of radon. The results reported here reveal that the occupational exposure in Urşilor, Vadu Crişului, Tȃuşoare, Vântului, and Muierii caves needs to be carefully monitored. The effective doses to workers vary between an average of 0.25 and 4.39 mSv/year depending on the measuring season. The highest values were recorded in show caves, ranging from 1.15 to 6.15 mSv/year, well above the European recommended limit, thus posing a potential health hazard upon cave guides, cavers, and scientists.
Variations in radon dosimetry under different assessment approaches in the Altamira Cave
Journal of Radiological Protection, 2020
Caves' atmosphere is a special environment where it is necessary taking into account some of its characteristics to assess the radon dose. Equilibrium factor between radon and its progeny and, especially its unattached fraction are key parameters in radon dose evaluation. In order to consider the specific features of the Altamira Cave atmosphere, the radon and particles concentration has been measured. The mean annual radon concentration inside the cave over the period 2013-2019 is around 3500 Bq m-3 with an standard deviation of 1833 Bq m-3 and exhibits seasonal variations. This value surpass all international (WHO, IAEA, ICRP) upper action and reference levels (occupational and non occupational). Dose rate levels expressed in µSv h-1 were estimated for four different equilibrium scenarios between radon and its progenies 218 Po, 214 Pb, 214 Bi and 214 Po. Newest dose conversion factors (DCF) have been used and the contribution made to the dose by the unattached fraction of radon progeny has been also assessed from the particle concentration. The results suggest that the mean annual dose levels show variations of up to 500% due to the range of the equilibrium factors (F), and the unattached fraction (fp) considered in this study. Given the high radon concentrations usually found in show caves, the best way to reduce this variability and its associated uncertainty in dose assessment is to conduct specific studies aimed to determine both the equilibrium factor and the unattached fraction of progenies.
Indoor radon levels in underground workplaces of Catalonia, Spain
Radiation Measurements, 2008
In Spain, according to the 96/29/EURATOM Directive of the European Commission, the regulations of protection against ionising radiation (Real Decreto 783/2001) establish for the first time the need of monitoring those workplaces that might have high radiation levels from natural radionuclides. In this context, a systematic survey has been carried out in Catalonia in which the annual-averaged radon concentration has been determined in 13 underground workplaces. Two sites have been identified as having radon levels higher than the 1500 Bq m −3 suggested by the ICRP as the maximum value for an action level. In two other sites a more detailed study is required to determine whether the dose received by the workers constitutes a significant increment of the exposure to natural radioactivity from the radiation protection point of view.
Two significant experiences related to radon in a high risk area in Spain
Radon is a natural radioactive gas and it is currently accepted as being responsible for lung cancer in some cases. One of the most important sources of indoor radon is from the soil. The radium content of soil is also a very important factor to be taken into account. The natural radiation map of Spain (MARNA) classifies the country into three regions with different levels of natural gamma radiation. There are some areas in Spain with high levels of natu- ral radiation one of those is the province of Salamanca. Western part of this province presents a population of 20 000 inhabitants and 7% of the houses have an indoor radon concentration above 400 Bq·m–3. In this high risk area, the village of Villar de la Yegua is of special interest: 11% of the houses in this village have an indoor radon level below 400 Bq·m–3, 89% have above 400 Bq·m–3 and 71% of the houses have a radon concentration above 1000 Bq·m–3. An old uranium mine site close to this village has been selected for the construction of an experimental pilot house. It is a two story house located in the place with a very high 226Ra concentration in soil. Radon in soil at 1 m depth has an average level of 250 kBq·m–3. We present in this work the characteristics of the experimental unit located in this high risk area and we describe the zone where one of the Spanish villages with the highest radon concentration is located. This is a very interesting place for further research on indoor radon concentration and it is a unique opportunity of testing radon monitors, radon passive detectors and remedial actions for the mitigation of radon in real conditions. It is common to carry out intercomparison exercises under laboratory conditions. Nonetheless, it is not so common to develop these exercises in real conditions as we have in the experimental unit we present here. We offer in this work the possibility for other research groups of testing their equipments in this unit and we also show the evolution of the works carried out in the locality of Villar de la Yegua.
Cave radon exposure, dose, dynamics and mitigation
2021
Many caves around the world have very high concentrations of naturally occurring 222Rn that may vary dramatically with seasonal and diurnal patterns. For most caves with a variable seasonal or diurnal pattern, 222Rn concentration is driven by bi-directional convective ventilation, which responds to external temperature contrast with cave temperature. Cavers and cave workers exposed to high 222Rn have an increased risk of contracting lung cancer. The International Commission on Radiological Protection (ICRP) has re-evaluated its estimates of lung cancer risk from inhalation of radon progeny (ICRP 115) and for cave workers the risk may now (ICRP 137) be 4–6 times higher than previously recognized. Cave Guides working underground in caves with annual average 222Rn activity 1,000 Bq m3 and default ICRP assumptions (2,000 workplace hours per year, equilibrium factor F 0.4, dose conversion factor DCF 14 μSv (kBq h m3)1 could now receive a dose of 20 mSv y1. Using multiple gas ...