A Preliminary Study of Radon Equilibrium Factor at a Tourist Cave in Okinawa, Japan (original) (raw)
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Uncertainties in the evaluation of the dose coming from radon in tourist caves
Indoor radon poses a health risk confirmed by a variety of studies. High concentrations of this gas can be found in closed enclosures depending on several factors like activity of source term, permeability of the source/indoor air inter-phase, as well as the interchange rate of external air. Low ventilation rates together with the presence of 226-Ra in rocks, make the tourist caves a place where medium and high radon concentrations can typically be found. With the incorporation of EURATOM basic standards for radiological protection, into the national European legislations radon have been recognised as a health risk to be controlled in workplaces. The transfer of EURATOM standards to the Spanish legislation came out on Title VII (BOE 178/2001) where radiation coming from natural sources has an analogous role as radiation emitted from artificial ones.
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
International Journal of Speleology, 2005
The physical characteristics of radon are reported as well as its sources,the transport in rock and its behaviour in caves. Then, the instruments,both active and passive, used for the measurement of radon concentration are discussed by taking into account their respective advantages and disadvantages for the use in the cave environment. Since in many countries radon is the object of regulations that were adopted for radiation protection purposes, this aspect is examined and the recommendations issued by international organisations and enforced in different countries are reported. Materials, methods and other remarks on the limits implementation are also listed with the aim of providing the managers of show caves with some instruments to comply with the domestic requirements with the most convenient solution.
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...
The Health Hazard Evaluation Program received a technical assistance request from the U.S. National Park Service because they were concerned about potential exposures to radon and radon decay products at a tourist cave and a connected building. What We Did • We measured radon gas concentrations inside the visitor's center and other buildings in the park. • We measured the amount of radon and radon decay products inside of two caves. • We released tracer gas to determine how radon was entering the visitor's center.
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.
Radon Survey and Exposure Assessment in Karaca and Çal Caves, Turkey
Water Air and Soil Pollution, 2011
Radon concentration and gamma activity concentration of naturally occurring radionuclides were determined and presented for two tourist caves (Karaca and Çal caves) in this study. These caves are reported to receive about 77,000 visitors during the summer season in 2007. It was seen that mean radon activity concentrations for the winter and summer seasons for the Karaca cave is 1,023 and 823 Bq/m3 and for the Çal cave is 264 and 473 Bq/m3. Mean 226Ra, 232Th, and 40K activity concentrations are found to be 43, 19, and 262 Bq/kg for the Karaca cave and 31, 27, and 460 Bq/kg for the Çal cave. Doses received by the cave guides due to radon were estimated to be 2.9 mSv/year for the winter season and 2.3 mSv/year for the summer season for the Karaca cave. Same values were estimated for the Çal cave, and the results were found to be 0.6 mSv/year for the winter season and 1.1 mSv/year for the summer season. Annual effective doses received by the visitors in both caves were estimated to be in the order of μSv/year because of the short exposure time comparing the cave guides. Although the reported values are below the recommended values, both groups are exposed to possible radiological risk during their stay inside the cave, since prolonged exposure to high radon concentration has been linked to lung cancer.
Dependence of radon levels in Postojna Cave on outside air
2011
Postojna Cave is the largest of 21 show caves in Slovenia. The radon concentration there was measured continuously in the Great Mountain hall from July 2005 to October 2009 and ranged from about 200 Bq m −3 in winter to about 3 kBq m −3 in summer. The observed seasonal pattern of radon concentration is governed by air movement due to the difference in external and internal air densities, controlled mainly by air temperature. The cave behaves as a large chimney and in the cold period, the warmer cave air is released vertically through cracks and fissures to the colder outside atmosphere, enabling the inflow of fresh air with low radon levels. In summer the ventilation is minimal or reversed and the air flows from the higher to the lower openings of the cave. Our calculations have shown that the effect of the difference between outside and cave air temperatures on radon concentration is delayed for four days, presumably because of the distance of the measurement point from the lower entrance (ca. 2 km). A model developed for predicting radon concentration on the basis of outside air temperature has been checked and found to be successful.
MONITORING OF RADON LEVELS IN SOME TOURISTIC UNDERGROUND ENVIRONMENTS FROM ROMANIA
The purpose of this research is to provide the distribution of radon levels in three underground environments of tourist interest from Romania (" Urşilor " Cave, " Muierilor " Cave and Turda Salt Mine). This study is of great interest since it identifies the values that could present a potential long-term health risk for the full-time staff (guides) spending extended periods conducting tours or carrying out maintenance within these underground environments and less for tourists. Furthermore, a possible relationship between the radon values and the local geology was disscused. Indoor radon concentrations were measured by using solid state CR-39 type RSKS nuclear track-etch detectors that were exposed from 3 to 6 months. The results reveal low radon levels in salt mine with the annual average concentration below the detection limit (around 8 Bq m-3), related to the salt plastic rock without fissures, fractures and consequently, without circulation pathways for radon into the salt mine chambers. This type of environment is proper to be used for speleotheraphy and spa tourism. " Muierilor cave " has relatively low radon concentration varying between 63 and 172 Bq m-3 , with only one value of 1184 Bq m-3 , as compared with " Urșilor " Cave, which values are in the range of 783-1795 Bq m-3 indicating the need of further long term monitoring by using both the passive and the active methods. Our results are comparable with radon concentration in different underground environments reported from other European surveys, lower than many of them. Geological background of these areas could sustain the measured values, on the one side due to the presence of granitic plutons and even the uraniferous mineralizations proximity, and on the other side due to the presence of limestone and its gneiss and mica-schist rocks basement that causes the low diffusion coefficient of radon.
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 ...