Equilibrium Equivalent Radon Concentration Research Articles

MEASUREMENT OF RADON, THORON AND THEIR PROGENY IN DIFFERENT TYPES OF DWELLING IN ALMORA DISTRICT OF KUMAUN HIMALAYAN REGION.

The indoor concentrations of radon (222Rn), thoron (220Rn) and their daughter products were measured in the dwellings of Almora district in Kumaun Himalaya, India using pin-hole dosemeters and deposition progeny sensors. The measurements were made in the residential houses built of mud, stone with cement plaster and cemented house during winter season. Average [geometric mean (GM) values] radon and thoron concentrations for all dwellings were found to be 99.82 and 79.70 Bq m-3, respectively, while average equilibrium equivalent radon concentration and equilibrium equivalent thoron concentration (measured for the first time for this region) were measured at 35.22 and 2.52 Bq m-3, respectively. Radon concentration (GM values) was found to be 110.73, 97.00 and 93.85 Bq m-3 for mud houses, stone with cemented plaster houses and cemented houses, respectively. On the other hand, thoron concentration values were 87.10, 75.79 and 75.68 Bq m-3 for cemented houses, mud houses and stone with cemented plaster houses, respectively. Interpretations have been made on the basis of measured radon/thoron and progeny concentration values with respect to the difference of construction material of the dwellings.

Indoor radon monitoring in the Mandi district of Himachal Pradesh, India, for health hazard assessment

In the present study, indoor radon equilibrium equivalent concentration monitoring was carried out using Solid-State Nuclear Track Detectors in some residential areas of the Mandi district, Himachal Pradesh, India. The average value of the indoor radon equilibrium equivalent concentration in the study area was found to be 94 Bq m -3 , with an annual effective dose of 1.61 mSv. The average value of the indoor radon equilibrium equivalent concentration in the studied areas was found to be higher than the world average indoor radon value of 40 Bq m -3 but lower than the value of the action level 300 Bq m -3 , except for two locations.

Long-term measurements of radon, thoron and their airborne progeny in 25 schools in Republic of Srpska

This article reports results of the first investigations on indoor radon, thoron and their decay products concentration in 25 primary schools of Banja Luka, capital city of Republic Srpska. The measurements have been carried out in the period from May 2011 to April 2012 using 3 types of commercially available nuclear track detectors, named: long-term radon monitor (GAMMA 1)- for radon concentration measurements (CRn); radon-thoron discriminative monitor (RADUET) for thoron concentration measurements (CTn); while equilibrium equivalent radon concentration (EERC) and equilibrium equivalent thoron concentrations (EETC) measured by Direct Radon Progeny Sensors/Direct Thoron Progeny Sensors (DRPS/DTPS) were exposed in the period November 2011 to April 2012. In each school the detectors were deployed at 10 cm distance from the wall. The obtained geometric mean concentrations were CRn = 99 Bq m−3 and CTn = 51 Bq m−3 for radon and thoron gases respectively. Those for equilibrium equivalent radon concentration (EERC) and equilibrium equivalent thoron concentrations (EETC) were 11.2 Bq m−3 and 0.4 Bq m−3, respectively. The correlation analyses showed weak relation only between CRn and CTn as well as between CTn and EETC. The influence of the school geographical locations and factors linked to buildings characteristic in relation to measured concentrations were tested. The geographical location and floor level significantly influence CRn while CTn depend only from building materials (ANOVA, p ≤ 0.05). The obtained geometric mean values of the equilibrium factors were 0.123 for radon and 0.008 for thoron.

Assessment of radiological parameters and radiation dose received by the miners in Jaduguda uranium mine, India

Monitoring of radiological parameters in underground uranium mines is essential to maintain the radiation levels within safe limits. In this study, the radiological parameters such as external gamma emitted from ore body, long-lived alpha activity associated with ore dust and radon concentration in an operating underground uranium mine located at Jaduguda, India were measured using different equipments such as micro-R radiation survey meter, personal air sampler and scintillation cell. The geometric mean values of external gamma radiation level, long-lived alpha activity, radon activity concentration and equilibrium equivalent radon (EER) concentration were found to be 2.39μGyh−1, 16.84mBqm−3, 872.89Bqm−3 and 436.44Bqm−3 respectively with their geometric standard deviations of 1.56, 3.21, 1.58 and 1.58. The total radiation dose received by the miners estimated from the radiological parameters was found to be well below the prescribed limit of 20mSvy−1 recommended by International Commission on Radiation Protection (ICRP), and hence, it may not pose significant health hazards to the Jaduguda miners.

Seasonal behavior of radon decay products in indoor air and resulting radiation dose to human respiratory tract

Most of radiation hazard of indoor radon is largely due to the radon progenies, which are inhaled and deposited in the human respiratory tract. It is essential to evaluate aerodynamic characteristics of the radon progenies, which are either attached or unattached to aerosol particles, because the dose is strongly dependent on the location of deposition in respiratory tract and hence on the aerodynamic characteristics of the aerosol particles. This paper presents the seasonal behavior of radon decay products in indoor air under domestic conditions at Nagoya University, Japan. A low pressure cascade impactor as an instrument for classifying aerosol sizes and imaging plate as a radiation detector have been employed to characterize the activity size distribution of short-lived radon decay products. In parallel, radon and its progenies concentrations were measured. Taking into account the progeny characteristics, the inhalation dose in the different seasons was also estimated based on a lung dose model with the structure that is related to the ICRP66 respiratory tract model. The result evident that, the highest dose 0.22 mSvy−1 was observed during the winter where the highest value of equilibrium equivalent concentration of radon (EEC) and lowest value of the activity median aerodynamic diameter (AMAD) were found in this season; whereas, the dose in spring appeared to be lowest 0.02 mSvy−1.

Evaluation of effect of ventilation on radon concentration and occupational exposure to radon daughters in low ore grade underground uranium mine

This study aims to evaluate the effect of various ventilation parameters on radon concentration and inhalation exposure of miners in underground uranium mines. The study carried out at Jaduguda mine revealed that the airflow rate plays a significant role in controlling the radon and its daughter concentrations in the mine. The equilibrium equivalent radon concentration in the mine stopes varied from 180 to 402 Bq m−3. Under existing ventilation condition of the mine, the average inhalation exposure of miners was estimated to be 0.42 WLM year−1, which is about 10 % of the current threshold limit of 4 WLM year−1.

Measurement of Radon Concentrations and Annual Dose Rate in some Regions of Baghdad City using LR-115 Nuclear Track Detector

In this work, LR-115 solid state nuclear track detector used to measure the indoor and outdoor radon concentrations, the annual absorbed dose rate and annual effective dose rate to the lung, were measured in nine houses at different places of Baghdad city, the observed values of indoor and outdoor radon concentrations was in range of 14.7-46.17 Bq/m 3 and 9.69–35.69 Bq/m 3 respectively. The resulting concentration of Short-lived radon daughters expressed in term of an equilibriumequivalent radon concentration (EEC), the minimum and maximum indoor results of (EEC) was 5.88-18.46 Bq/m 3 and the outdoor results was 6.78-24.98 Bq/m 3 . The Potential Alpha Energy (PAE) concentration expressed in Working Level (WL) units was in the range of 1.58-4.99 mWL in indoor and 1.8-6.75 mWL in outdoor regions. The annual effective dose calculated according to the radiation weighting (WR) factor for alpha particles and the tissue weighting (WT) factor and the annual absorbed dose rate, the present results confirmed that the radon gas concentrations in all the nine places of Baghdad city are lower than the International Commission Radiation Protection (ICRP) agency, recommended value (200Bq/m 3 ).

Results from time integrated measurements of indoor radon, thoron and their decay product concentrations in schools in the Republic of Macedonia.

As part of a survey on concentrations of radon, thoron and their decay products in different indoor environments of the Balkan region involving international collaboration, measurements were performed in 43 schools from 5 municipalities of the Republic of Macedonia. The time-integrated radon and thoron gas concentrations (CRn and CTn) were measured by CR-39 (placed in chambers with different diffusion barriers), whereas the equilibrium equivalent radon and thoron concentrations (EERC and EETC) were measured using direct radon-thoron progeny sensors consisting of LR-115 nuclear track detectors. The detectors were deployed at a distance of at least 0.5 m from the walls as well as far away from the windows and doors in order to obtain more representative samples of air from the breathing zone; detectors were exposed over a 3-month period (March-May 2012). The geometric mean (GM) values [and geometric standard deviations (GSDs)] of CRn, CTn, EERC and EETC were 76 (1.7), 12 (2.3), 27 (1.4) and 0.75 Bq m(-3) (2.5), respectively. The equilibrium factors between radon and its decay products (FRn) and thoron and its decay products (FTn (>0.5 m)) were evaluated: FRn ranged between 0.10 and 0.84 and FTn (>0.5 m) ranged between 0.003 and 0.998 with GMs (and GSDs) equal to 0.36 (1.7) and 0.07 (3.4), respectively.

Long-term simultaneous measurement of indoor concentration of radon and thoron progeny in the dwellings of Una and Hamirpur District of Himachal Pradesh

Long-term simultaneous measurement of indoor concentration of radon and thoron progeny is made using passive alpha track detectors in the dwellings of Una and Hamirpur district of Himachal Pradesh. The preliminary results of these measurements are reported, particularly regarding direct thoron progeny sensor (DTPS) and direct radon progeny sensor (DRPS) being set up in real field conditions for the first time in Himachal Pradesh. The concentrations of radon and thoron progenies (equilibrium equivalent radon and thoron concentration (EERC/EETC)) were measured for all the seasons of the year. A remarkable finding is the positive correlation between EERC and EETC (R2 = 0.79 in summer and R2 = 0.81 in winter). A comparison was made with the measurements of EERC/EETC in summer and winter season. The ratio of EETC/EERC was calculated and this agrees with worldwide range. This study contributes to the status of Himachal Pradesh in the mapping of radon in India.

Outdoor 222Rn-concentrations in Germany – part 1 – natural background

To determine the natural radiation exposure due to outdoor radon (222Rn) and its short-lived decay products in Germany, the Federal Office for Radiation Protection (BfS) conducted a measuring programme over three years. The annual mean radon concentration at 1.5 m above ground level was measured with solid-state track etch detectors at 173 measuring points in an even grid with a grid length of approx. 50 km. Furthermore, annual mean values of the equilibrium-equivalent radon concentration (EEC) and the equilibrium factor were estimated on the basis of the activity concentrations of 214Pb and 214Bi measured at 27 stations of the German Meteorological Service (DWD). Our study yielded a spatial mean outdoor radon concentration for Germany of 9 ± 1 Bq m−3 (median: 8 (−0.5/+1.0) Bq m−3), with regional means varying from 4.5 Bq m−3 in Hamburg to 14 Bq m−3 in Bavaria. The determined EEC are in a range from 1.4 to 11 Bq m−3.

Field experience on indoor radon, thoron and their progenies with solid-state detectors in a survey of Kosovo and Metohija (Balkan region)

Since 1996/97, indoor radon has been measured in scattered locations around Kosovo. In the most recent campaign, apart from radon, thoron and Rn and Tn progenies have also been measured. The current survey involves 48 houses, in which different detectors have been deployed side-by-side in one room, in order to measure indoor radon and thoron gas with RADUET devices based on CR-39 detectors (analysed by Japanese collaborators) and with direct thoron and radon progeny sensor (DTPS and DRPS) devices based on LR-115 detectors (analysed by collaborators from India). Estimated arithmetic mean values of concentrations in 48 houses are 122 Bq m(-3) for radon and 136 Bq m(-3) for thoron. Those for equilibrium equivalent radon concentration and equilibrium equivalent thoron concentration based on measurements in 48 houses are 40 and 2.1 Bq m(-3), respectively. The arithmetic mean value of the equilibrium factor is estimated to be 0.50 ± 0.23 for radon and 0.037 ± 0.041 for thoron. The preliminary results of these measurements are reported, particularly regarding DTPS and DRPS being set up in real field conditions for the first time in the Balkan region. The results are to be understood under the caveat of open questions related to measurement protocols which yield reproducible and representative results, and to quality assurance of Tn and Rn/Tn progeny measurements in general, some of which are discussed.

Lung dosimetry of inhaled radon progeny in mice

Biological response of exposure to radon progeny has long been investigated, but there are only few studies in which absorbed doses in lungs of laboratory animals were estimated. The present study is the first attempt to calculate the doses of inhaled radon progeny for mice. For reference, the doses for rats and humans were also computed with the corresponding models. Lung deposition of particles, their clearance, and energy deposition of alpha particles to sensitive tissues were systematically simulated. Absorbed doses to trachea and bronchi, bronchioles and terminal bronchioles, alveolar-interstitial regions, and whole lung were first provided as a function of monodisperse radon progeny particles with an equilibrium equivalent radon concentration of 1 Bq m(-3) (equilibrium factor, 0.4 and unattached fraction, 0.01). Based on the results, absorbed doses were then calculated for (1) a reference mine condition and (2) a condition previously used for animal experiments. It was found that the whole lung doses for mice, rats, and humans were 34.8, 20.7, and 10.7 nGy (Bq m(-3))(-1) h(-1) for the mine condition, respectively, while they were 16.9, 9.9, and 6.5 nGy (Bq m(-3))(-1) h(-1) for the animal experimental condition. In both cases, the values for mice are about 2 times higher than those for rats, and about 3 times higher than those for humans. Comparison of our data on rats and humans with those published in the literature shows an acceptable agreement, suggesting the validity of the present modeling for mice. In the future, a more sophisticated dosimetric study of inhaled radon progeny in mice would be desirable to demonstrate how anatomical, physiological, and environmental parameters can influence absorbed doses.

A new technique for measuring the concentrations of airborne radon progeny by using an imaging plate

A new technique was developed for measuring the concentrations of airborne radon progeny by using an imaging plate (IP). The concentrations of radon progeny collected on the sampling filter were measured with the IP at 2-5-, 6-20- and 21-30-min intervals after sampling, and the alpha disintegrations were automatically counted by a self-developed image analysis software. To reduce the overlapping impact on alpha counts, a plastic separator with a 0.5-mm thickness was set between the sampling filter and the IP. The lower limit of detection for the equilibrium equivalent concentration of radon was estimated to be ∼3.5 Bq m(-3) for a 10-min sampling at 10 l min(-1). Comparison experiments showed that results measured with the new technique were well consistent with those measured with the alpha spectrometer. It indicates that the new technique is a useful method for accurate measurements of airborne radon progeny concentrations.

Comparative dosimetry of radon and thoron

There is a well-known discrepancy between dosimetrically derived dose conversion factor (DCF) and epidemiologically derived DCF for radon. As the latter DCFs, International Commission on Radiological Protection (ICRP) recommends a value of ∼6.4 nSv (Bq h m(-3))(-1) and 7.9 nSv (Bq h m(-3))(-1) for radon decay products (RnDP) in dwellings and workplaces, respectively. On the other hand, the dosimetric calculations based on the ICRP-66 respiratory tract model derived a DCF of 13 nSv (Bq h m(-3))(-1) and 17 nSv (Bq h m(-3))(-1) for RnDP in dwellings and workplaces, respectively, and 83 nSv (Bq h m(-3))(-1) for thoron decay products (TnDP) in dwellings. In addition, the DCFs derived from both approaches and UNSCEAR were applied to comparative dosimetry for two thoron-enhanced areas (cave dwellings in China and dwellings at a spa town in Japan), where the equilibrium equivalent concentration of radon and equilibrium equivalent concentration of thoron have been measured. In the case of the spa town dwellings, the dose from TnDP was larger than the dose from RnDP.

5039 3D-CT lymphography guides the sentinel node biopsy after preoperative systemic chemotherapy

This article reports results of the first investigations on indoor radon, thoron and their decay products concentration in 25 primary schools of Banja Luka, capital city of Republic Srpska. The measurements have been carried out in the period from May 2011 to April 2012 using 3 types of commercially available nuclear track detectors, named: long-term radon monitor (GAMMA 1)- for radon concentration measurements (CRn); radon-thoron discriminative monitor (RADUET) for thoron concentration measurements (CTn); while equilibrium equivalent radon concentration (EERC) and equilibrium equivalent thoron concentrations (EETC) measured by Direct Radon Progeny Sensors/Direct Thoron Progeny Sensors (DRPS/DTPS) were exposed in the period November 2011 to April 2012. In each school the detectors were deployed at 10 cm distance from the wall. The obtained geometric mean concentrations were CRn = 99 Bq m−3 and CTn = 51 Bq m−3 for radon and thoron gases respectively. Those for equilibrium equivalent radon concentration (EERC) and equilibrium equivalent thoron concentrations (EETC) were 11.2 Bq m−3 and 0.4 Bq m−3, respectively. The correlation analyses showed weak relation only between CRn and CTn as well as between CTn and EETC. The influence of the school geographical locations and factors linked to buildings characteristic in relation to measured concentrations were tested. The geographical location and floor level significantly influence CRn while CTn depend only from building materials (ANOVA, p ≤ 0.05). The obtained geometric mean values of the equilibrium factors were 0.123 for radon and 0.008 for thoron.

Mitigation of the effective dose of radon decay products through the use of an air cleaner in a dwelling in Okinawa, Japan

Field measurements were conducted to assess the effects of an air cleaner on radon mitigation in a dwelling with a high radon concentration in Okinawa, Japan. The measurements included indoor radon concentration, individual radon progeny concentration, equilibrium equivalent concentration of radon (EECRn), unattached fraction, and size distribution of aerosol-attached radon progeny. These measurements were conducted in a 74 m 3 room with/without the use of an air cleaner. The results showed that the mean radon concentration during the measurement was quite high (301 Bq m −3). The operation of air cleaner decreased the radon progeny activity concentration, EECRn and equilibrium factor by 33%, 57% and 71%, respectively, whereas the unattached fraction increased by 174%. In addition, the activity concentration of attached radon progeny in the accumulation mode (50–2000 nm) was obviously deceased by 42%, when the air cleaner was operated. According to dosimetric calculations, the operation of air cleaner reduced the effective dose due to radon progeny by about 50%.

Radon mitigation using an air cleaner

Room experiments were conducted to investigate the effects of an air cleaner on radon mitigation. Radon concentration, equilibrium equivalent radon concentration and unattached fraction were measured during the experiments. Two types of filtration were tested using the air cleaner which has a high efficiency particulate air filter (HEPA-filter) and a deodorizing activated carbon (carbon-filter). One is the filtration with the HEPA-filter plus carbon-filter and the other is the filtration with only the HEPA-filter. The effective doses from radon progeny were significantly decreased. Both filtration methods were effective for the mitigation of effective dose due to radon progeny.

Monitoring radon and its progeny in the environment of the vertical 15 UD Pelletron accelerator facility

Environmental radioactivity due to radon and its progenies in the ambient air at the vertical 15 UD Pelletron accelerator facility of the Inter University Accelerator Centre, New Delhi, India was evaluated to calculate the annual effective dose to the workers and users. The radon activity was measured with an active monitor. The activity concentrations of the radon progenies were measured simultaneously using grab aerosol sampling and absolute beta counting. The effect of in situ meteorological parameters such as the temperature and relative humidity along the height of the Pelletron tower on the activity of radon and its progenies was studied. The measurements were carried out in the winter and rainy seasons. The values for the temperature, relative humidity (in percentage), radon activity concentration, radon Equilibrium Equivalent Concentration (EEC), annual exposure, annual inhalation and annual effective dose were recorded/calculated for locations with air conditioning and without air conditioning. Elements such as 218Po, 214Pb, 214Bi, radon and EEC activity concentrations were found to decrease with the height and relative humidity and increase with increasing temperatures. The dose levels observed in the facility were below the International Commission on Radiological Protection (ICRP) and United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) recommendations, even for the general public (1.2 mSv).

QA programme for radon and its short-lived progeny measuring instruments in NRPI Prague

To subserve the institutional research and tasks coming out from the Czech National Radon Programme, a new QA programme to calibrate all the known types of devices that measure radon and its short-lived progeny was developed at the Department of Radon mobile group of the National Radiation Protection Institute (NRPI) at Prague. The programme also included calibration of instruments measuring a unique quantity of unattached and attached fractions of short- lived radon progeny Generally, NRPI declares estimation of radon concentration during all routine calibration measurements with an overall uncertainty <5% (one sigma) and of equilibrium-equivalent radon concentration with an overall uncertainty <10% (one sigma). The results of the comparative measurements of the unattached and attached fractions of each short-lived radon progeny carried out with a comparing continuous monitor Fritra 4 in the German reference radon chamber at PTB Braunschweig indicated an acceptable level of agreement, up to 10%.

Variation of indoor radon progeny concentration and its role in dose assessment

Instantaneous measurements of equilibrium equivalent concentration of radon (EEC Rn) were taken over a period of 1 year in 2004 in a typical house at Amritsar city, located in the northwest part of India. A method based on absolute beta counting subsequent to grab aerosol sampling was used. During that year, EEC Rn varied between 1.56 Bq m −3 and 22.77 Bq m −3 with average value of 8.76 Bq m −3. EEC Rn decreased with the transition from winter to summer and vice versa, having a negative correlation with outdoor temperature. The use of mechanical ventilation, under normal living conditions during summer, caused an extra decrease in the concentrations. The variations with temperature and mechanical ventilation are discussed. Some major issues related to the uncertainties in dose calculations caused by the lack of knowledge of equilibrium factor and ignoring the effect of life style on the radon and its progeny concentrations are discussed.