Equilibrium Equivalent Concentration Research Articles

Variation of radon ( [formula omitted]Rn) progeny concentrations in outdoor air as a function of time, temperature and relative humidity

A sensitive grab sampling technique was used to measure the equilibrium equivalent concentration of radon ( 222 Rn) progeny, EEC Rn , outdoors at Bathinda, Punjab (India), over a period of 6 months. The method was based on the beta counting of aerosol samples collected on glass micro-fiber filters by drawing the air through the filters. Measurements, covering two of the three sessions of the day (morning, afternoon, evening), were performed two times per day at a fixed place at a height of 1.8 m above the ground surface. The total average value of EEC Rn was 5.62 Bq m - 3 , while the morning, afternoon and evening averages were 9.15, 2.85 and 5.33 Bq m - 3 , respectively. Negative correlation was observed for air temperature and EEC Rn , while positive correlation was found for relative humidity and EEC Rn , EEC Rn was higher in winter than in summer.

Radon and thoron exposures for cave residents in Shanxi and Shaanxi provinces.

Measurements of natural radiation were carried out in cave dwellings distributed in the Chinese loess plateau. Those dwellings are located in Shanxi and Shaanxi provinces. Radon and thoron gas concentrations were measured using a passive integrating radon-thoron discriminative detector. Concentrations of thoron decay products were estimated from measurements of their deposition rates. A detector was placed at the center of each dwelling for 6 months and replaced with a fresh one for another 6 months. Measurements were conducted in 202 dwellings from August 2001 through August 2002. A short-term measurement was conducted during the observation period. In addition, gamma-ray dose rates were measured both indoors and outdoors with an electronic pocket dosimeter. Radioactivities in soil were determined by gamma-ray spectrometry with a pure germanium detector. Among 193 dwellings, indoor radon concentrations ranged from 19 to 195 Bq m(-3) with a geometric mean (GM) of 57 Bq m(-3), indoor thoron concentrations ranged from 10 to 865 Bq m(-3) with a GM of 153 Bq m(-3), and indoor equilibrium equivalent thoron concentrations ranged from 0.3 to 4.9 Bq m(-3) with a GM of 1.6 Bq m(-3). Arithmetic means of the gamma-ray dose rates were estimated to be 140 nGy h(-1) indoors and 110 nGy h(-1) outdoors. The present study revealed that the presence of thoron is not negligible for accurate radon measurements and thus that special attention should be paid to thoron and its decay products for dose assessment in such an environment. More systematic studies are necessary for a better understanding of thoron and its decay products.

Using an Imaging Plate to Measure the Concentration of Radon Progeny in Air

A simple technique was developed for using an imaging plate (IP) to estimate the individual concentrations of radon progeny in the air. The objective of this technique is to survey concentrations in high-humidity environments, such as caves, utility mains, and underground facilities.An IP called BAS-III, which performs well in extremely humid environments, was selected. The sampling flow rate was 65 liters per minute by a 47 mm-dia. glass-fiber filter (GF/F), and the grab sampling time was determined to be 5-10 minutes. One minute after the air sampling, the surface of the filter was attached directly to the IP in a prepared cassette. This was repeated six times for 10 minutes, for a total exposure of 60 minutes. Six values of Photo-Stimulated Luminescence (PSL) indicating the decay curve of the radon progeny sampled on the filter were analyzed. In environments with extremely high concentrations of radon, more accurate measurements can be obtained by making a simple distinction between PSL values for α and β rays. The lower detection limit for the equilibrium equivalent concentration (EEC) of radon was estimated to be about 20 Bqm-3. This system can be successfully adopted in humid areas.

Concentrations of 222 Rn, Its Short-Lived Daughters And 212 Pb And Their Ratios Under Complex Atmospheric Conditions And Topography

Atmospheric activity concentrations of 212Pb and short-lived 222Rndaughters, together with meteorological elements, have been observed continuously atthree sites at Kamisaibara Village in Japan. In addition, atmospheric activity concentrationof 222Rn, equilibrium-equivalent concentration of 222Rn and conditionsof the lower atmosphere were observed for three intensive observation periods at Akawase,one of the three sites in Kamisaibara Village. The equilibrium-equivalent concentration of222Rn is almost the same as the atmospheric activity concentration of short-lived222Rn daughters.

Radon-222 in Brazil: an outline of indoor and outdoor measurements

This study discusses the methodology for measuring and assessing the radon concentration in indoor and outdoor environments. A research study was developed to investigate the long-term behavior of the diurnal and seasonal fluctuations of radon 222Rn EEC (Equilibrium-Equivalent Concentration) and the influence of temperature and other climatic aspects on this behavior. The study was performed by means of both integrated and instantaneous measurements of radon and its short-lived daughter products for a period of 1 year in an indoor environment in Rio de Janeiro city, Brazil (reference environment), with continuous measurement, using a radon monitor with an alpha spectrometry detector. For a single day, a variability of about 50% could be observed in the 222Rn EEC values measured on a hourly basis, with a maximum occurring early in the morning and a minimum in the afternoon. For the long-term period, seasonality is responsible for a two order of magnitude variability, with a maximum of 50 Bq.m −3 in winter (dry season) and a minimum of 0.5 Bq.m −3 in the summer months (wet season), outdoors. A negative correlation with temperature was observed. The conclusions of this experiment led to a survey of radon gas concentration in dwellings in Rio de Janeiro city, Brazil, in urban area with nearly 7 million inhabitants, through integrated sampling methods, using a Solid State Nuclear Track Detectors Technique (SSNTD). The study was conducted in different geomorphological locations in town. The radon gas concentration in Rio de Janeiro dwellings ranged from 5 Bq.m −3 to 200 Bq.m −3. A good correlation between indoor radon gas concentration and location of dwellings was observed. The seashore areas presented the lowest levels of indoor radon concentration, whereas the highest levels were found close to the mountains.

Temporal variation of radon progeny ratio in outdoor air.

This paper investigates the concentration ratio of radon progeny (218Po, 214Pb, and 214Bi) in outdoor air. From 1988 to 1998, alpha spectroscopy was used intermittently to collect progeny data outside the author's office located in the northeastern part of Japan. Let the quantity R(EEC) represent the ratio EEC(218Po)/[EEC(214Pb) + EEC(214Bi)], where, e.g., EEC(218Po) denotes the equilibrium equivalent radon concentration contributed by 218Po. The concentration ratio R(EEC) correlates with outdoor air stability. Statistical and time series analyses of R(EEC) indicate (1) outdoor air is more stable in the morning than in the afternoon, (2) outdoor air is more stable in summer/autumn than in winter/spring, and (3) in spite of no significant correlation between R(EEC) and wind speed, the power spectrum of R(EEC) appears similar to that of wind speed. This is probably due to the fact that near-surface mixing is not very sensitive to wind speed.

A Simple Measurement Technique of the Equilibrium Equivalent Thoron Concentration with a CR-39 Detector.

A simple alpha-track measurement technique for the equilibrium equivalent thoron concentration (hereafter called EETC) using a CR-39 detector was discussed. Detection properties of the CR-39 detector were examined with regard to detection efficiencies for incident energy and angles, respectively. Since more than 90% of the EETC is dominated by the 212Pb concentration, its practical evaluation can be achieved even though the 212Bi concentration is ignored. In this technique, the CR-39 detector is directly placed on a filter after an air sample is taken and an adequate time elapses (radon progeny completely decay). In order to confirm the reliability of measured values, the technique was compared with an alpha spectroscopic method. There was a relatively good agreement between the two.

Indoor radon level in the dwellings of the Rajshahi and Chuadanga regions of Bangladesh

The indoor radon level in terms of equilibrium equivalent concentration (EEC) has been measured for dwellings in the Rajshahi region of Bangladesh as well as its adjoining Chuadanga region. The data were obtained using the passive time integrated method employing LR-115 (Type II) solid state nuclear track detectors. The geometric mean value for the EEC in the dwellings located in the Rajshahi region was obtained as 32.4±7.1 Bq m −3 and for the dwellings in the Chuadanga region was obtained as 27.3±6.2 Bq m −3 . The data obtained in the present work are compared with indoor radon levels prescribed by the International Commission on Radiation Protection.

Diurnal and seasonal variation of the equilibrium state between short-lived radon decay products and radon gas in ground-level air.

To study seasonal and diurnal variations and the effect of meteorological parameters, the equilibrium factor F (i.e. the ratio of equilibrium equivalent radon daughter concentration and radon gas concentration) was determined as a result of measurements on a test field at Munich-Neuherberg, Germany, continuously from October 1995 through March 1997. On average, F was found to be 0.62+/-0.09 (95% confidence level). The time series of F showed no distinct seasonal variations. Nevertheless, typical diurnal variations as well as seasonal variations of the diurnal behaviour were observed. Generally, F was found to be increased in the early afternoon, i.e. under conditions of enhanced vertical mixing in the atmosphere. The daily differences between high and low values of F depended on the season. On average, low F values were characteristic for days with precipitation and high wind speed, i.e. under turbulent atmospheric conditions. Therefore, taking daily mean values into account, F was found to be positively correlated with the aerosol concentration, although a relationship between the diurnal behaviour of the aerosol concentration and that of F was not detectable.

Time Variation of the Radon Equilibrium Factor in a Reinforced Concrete Dwelling

The time variation of the F value (equilibrium factor) was estimated for one year in a typical Japanese apartment of reinforced concrete using the following equipment: a 300 ml flow-through scintillation flask for the hourly variation of radon concentration and a WL meter for the equilibrium equivalent concentration of radon (EEC Rn). These monitors operated for four to eight days at the end of each month, and the information obtained was assumed to be the representative value for each month. The annual mean of F = 0.43 ± 0.09 found for the dwelling agrees very well with the UNSCEAR value of 0.4 for indoors. In addition, it appears that the monthly F value in the dwelling varies over the range by a factor of 3. In addition the tendency of the seasonal variation in the other countries located at middle geographical latitudes is also observed in Japan. The variation of the F value in this case is mainly based on the changes in the life styles and activities of the inhabitants, especially the ventilation condition of the room due to opening/shutting of windows and air-conditioner operation. In seasons when windows were shut, the F value increased: when the windows were open or the air-conditioners were on, the F value decreased, especially when the EEC Rn decreased as a result of the filtration effect. If it is necessary to determine the radon effective dose over a shorter period than one year, the time variation of each physical or environmental parameter including F value should be taken into account.

Indoor Air as an Important Source for 210Pb Accumulation in Man

A pilot study was performed with measurements in a German, inhabited, two-family house, to obtain data on the correlation between the equilibrium equivalent radon concentration C eq and the 210 Pb concentration C Pb in indoor air. Aerosol samples were collected in various rooms of the house under conditions of low ventilation. The data indicate a linear correlation between C e and C Pb . A regression analysis, assuming such a relationship, resulted in the following equation: C Pb (in mBq.m -3 ) = 8.2 × 10 -3 C eq (in Bq.m -3 ) + 0.32. From this relationship it follows that in environments with enhanced radon concentrations direct inhalation of 210 Pb is an important source for 210 Pb accumulation in man. It was estimated that at an indoor 222 Rn concentration of 1000 Bq.m 3 , the 210 Pb uptake from inhalation amounts 32 mBq.d -1 of which 62% originates from the direct inhalation of 210 Pb. Only the remaining third can be attributed to inhaled short-lived radon progeny and to radon gas dissolved in body tissues. It is shown that, in addition to ingestion and even for elevated indoor radon concentrations, direct inhalation of indoor 210 Pb is a further important source of uncertainty, when in vivo measurements of the 210 Pb activity in the human body are used as a measure of cumulative radon exposure.

Environmental Radon and Thoron Progeny Concentrations in Fujan Province of China

Surveys of environmental radon and thoron progeny concentrations were carried out with the filter method in Fujian Province of China, where very high concentrations of 238 U and 232 Th in soil had been reported. The mean values of equilibrium-equivalent radon and thoron concentrations (EEC Rn and EEC Tn ) were 12.9 Bq.m -3 and 0.87 Bq.m -3 indoors, 9.7 Bq.m -3 and 0.39 Bq.m -3 outdoors in the general living environment. Very high concentrations of both radon and thoron progeny were observed in underground places and railway tunnels. The mean additional effective doses due to the inhalation of radon and thoron and their progeny were estimated to be 7.75 mSv.a -1 and 22.2 mSv.a -1 for workers in those places mentioned above. Furthermore, the diurnal/seasonal variations and height distributions of radon and thoron progeny were also studied.

Temporal variation of thoron decay product concentration in the atmosphere and comparison with radon decay product concentration.

Seasonal and long-term variation of the airborne 212Pb concentration, representative of the equilibrium equivalent concentration of thoron decay products (EECRn220), was investigated from 1989 through 1996 at a semi-natural location in southern Germany. Continuous measurement yielded a long-term average concentration of 0.082 Bq m-3, while daily mean concentrations varied from < or = 0.01 to 0.34 Bq m-3. An average annual effective dose of 1.4 mSv due to outdoor thoron progeny concentration was estimated. This is about 2% of the dose due to the average short-lived radon progeny concentration (EECRn222) of 8.4 Bq m-3 measured for this location in the same period. In most years the seasonal pattern of 212Pb activity concentration in the atmosphere is characterized by two maxima: the first in May and the second one in September. Low concentrations are observed from November through February of each year. This is in contrast to the behaviour of the short-lived 222Rn progeny which exhibit enhanced concentrations exactly during these months. The most probable reason for the different temporal behaviour of 212Pb is the extremely reduced flux of thoron gas from the ground during the winter months.

Selectivity comparison of neutral carrier-based ion-selective optical and potentiometric sensing schemes

The selectivities of analogous carrier-based potentiometric and optical sensors are directly compared. This is done on the basis of recent developments in both fields that allow for a thermodynamically founded description of selectivity. Extended equations are shown that allow for the interconversion of selectivity values obtained with different definitions. The response of optodes toward different ions should generally be reported with the overall ion-exchange constants, K exch, together with the assumed stoichiometry of the formed complexes in the optical film. In addition, the selectivities for both sensing schemes can principally be reported with two sets of selectivity coefficients, K IJ pot and k IJ Psel for ion-selective electrodes and K IJ opt and k IJ Osel for optodes. While K IJ pot and K IJ opt values refer to the Nicolskii and Nicolskii-like selectivity coefficients, k IJ Psel and k IJ Osel values are obtained graphically as the horizontal distance of the separately measured calibration curves on a logarithmic activity scale. With ion-selective electrodes, the reporting of Nicolskii coefficient is generally preferred since such data are sample independent for Nernstian response slopes to all measured ions. In contrast, ion optode selectivities are preferably reported as k IJ Osel values since the continuous concentration changes within the optical film during measurement make Nicolskii-like selectivity coefficients generally sample-dependent. Nonetheless, the reporting of Nicolskii-like selectivities is recommended to compare optode and ISE selectivities. Care must be taken to choose equivalent equilibrium concentration ratios of complex and free ionophore in the sensing film for such comparative experiments. The clear distinction in symbols and formalisms allows one to avoid confusion in future reports on carrier-based ion sensors. Possible reasons why experimental selectivities may still deviate significantly from each other are discussed, as well as why one type of sensor may in some cases be a superior choice over the other.

Radon Risk Assessment in Slovak Kindergartens and Basic Schools

The results are presented of long-term measurements obtained during the radon survey in schools of the Slovak Republic. Measurements of equilibrium equivalent radon concentrations (EER) were performed in 645 buildings. It was found that the action level of EER was exceeded in 16 schools. Consequently short-term radon measurements were instituted in a kindergarten in Roznava-Cucma, where the highest level of EER was measured. The analysis of the results contains the comparison of the long- and short-term measurements, the influence of the spring and summertime, the daily radon variations and the radon source localisation. From the results obtained the annual effective doses from radon exposure, estimated for pupils and teachers in the kindergarten, were 7 mSv and 10.5 mSv, respectively. It is concluded that the real values of annual effective doses, estimated for pupils and teachers in schools are about 5 times lower than doses estimated from the results of integral long-term measurements due to the ventilation regime.

Efficient adsorption of waterborne short-lived radon decay products by glass fiber filters.

Glass fiber filters of a certain brand were found to be very efficient (retention > 95%) for adsorption of short-lived radon decay products during filtration of water. Carrier-free samples are obtained in a convenient geometry for efficient gross beta counting. Adsorption of "hot atoms" is not disturbed by the presence of "cold" lead ions. Approximate radioactive equilibrium between radon and its short-lived decay products may or may not exist in water at the source, but does exist after 3 h in PET bottles. These bottles are shown to be gas-tight for radon. Calibration of activity concentration in Bq L(-1) (radon gas concentration approximately equilibrium equivalent radon concentration) was performed by several standard procedures. Limit of detection is 2 Bq L(-1) within 10 min (total time) or 10 Bq L(-1) within 5 min for a net signal of 5 times standard deviation.

Outdoor Concentrations of the Equilibrium-Equivalent Decay Products of 222Rn in the Netherlands and the Effect of Meteorological Variables

Airborne radioactivity monitors put up in a network as a warning system in case of nuclear accidents were used to gain insight in the temporal variations of 222Rn and its decay products. Average equilibrium equivalent decay product concentrations (EEDCs) over a period of five years for stations across the country range from 1 to 3 Bq.m-3. Hourly averaged concentrations show a diurnal variation at all stations. The amplitude of this variation is maximal in summer and minimal or non-existent in winter. Superimposed is a seasonal variation with a maximum in late autumn and a minimum in spring. Wind velocity appears to be the major variable controlling the variation in EEDC in the outdoor environment of the Netherlands. Humidity seems to be correlated with the EEDC of 222Rn, probably because, due to plateout, a better equilibrium between 222Rn and its decay products is installed. Reduced EEDC during and shortly after rainfall seems to indicate a dilution of 222Rn in ground surface air due to enhanced vertical mixing below the rain cloud.

A Dynamic Compensation Method for Natural Ambient Dose Rate Based on 6 Years Data from the Dutch Radioactivity Monitoring Network

The significant variations in time exhibited by background radiation hinders a sensitive recognition of human-induced factors. A comprehensive study in the Netherlands has examined the influence of the various natural processes on the natural background using six years data from the Dutch nuclear emergency network. Results presented concentrate on temporal variations in ambient dose-equivalent rate, H*(10), and have led to simple expressions to model the ambient dose rate using a limited set of readily available parameters, i.e. air pressure, deposition rate and equilibrium equivalent decay product concentration of 222 Rn, EEDC. Best values and uncertainty ranges of the applied parameters are reported. Remaining variations, e.g. due to variations in the cosmic radiation intensity and the radon soil profile, are shown to be small in the Netherlands, with one exception when the cosmogenic dose rate at sea level was decreased for a period of months due to a global deflection of the earth's magnetic field in the summer of 1991. The resulting compensation method for the natural ambient dose rate enables sensitive detection of anomalies, supporting the surveillance of nuclear installations and the management of nuclear emergency networks.

Indoor radon concentrations in the town of Podgorica-Montenegro

Indoor radon survey in the town of Podgorica, capital of Montenegro, was performed in winter season 1994–1995. The town houses were classified on the basis of their construction materials and techniques in 4 distinct types. Radon was measured in 110 dwellings, selected with respect to the types and locations of houses. Measurements were carried out by cellulose nitrate track detectors, exposed for 90 days in living-rooms on ground floors. Equilibrium equivalent concentrations of radon are found to be in (4 – 453) Bq/m 3 range, with a median of 26.4 Bq/m 3. They belong to a log-normal distribution (geometric mean: 21.8 Bq/m 3, geometric standard deviation: 2.20 Bq/m 3). The detached houses built of bricks have the highest average indoor radon level, and the apartment houses made of concrete and bricks, with plaster on the walls, the lowest one.

Calculation procedure of potential alpha energy concentration with continuous air sampling.

A continuous potential alpha energy concentration monitor was developed to estimate the lung dose for inhalation of radon progeny. A silicon semiconductor detector was used as a detector. The build-up method was used and alpha particles emitted from 218Po, 214Po, 212Bi, and 212Po were detected. As 218Po and 212Bi have alpha particles of nearly the same energy, three detecting channels were set up. Counts corresponding to each nuclide were sent to a printer every 30 min. For the purpose of determining the potential alpha energy concentration of radon progeny continuously, a proper calculation procedure was investigated in detail. With this method, 218Po concentration and potential alpha energy concentration of radon progeny could be continuously obtained. The potential alpha energy concentration based on this procedure agreed well with that calculated from individual radon progeny concentration. When the measurement was done at 30-min intervals, the minimum detectable concentrations of 218Po concentration and equilibrium equivalent radon concentration were 0.3 Bq m(-3) and 0.15 Bq m(-3), respectively. The monitor can be used not only to estimate the lung dose but also to analyze environmental behavior of radon progeny.