Decay Product Concentrations Research Articles

Estimation of surface concentration of radon decay products from gamma dose rate change after rain

A method to estimate the surface concentration of radon decay products 214 Pb and 214 Bi from gamma dose rate changes due to rainfall has been developed. The conversion from the dose rate to surface concentration was performed by a dose rate model considering geometric conditions such as buildings and ground undulations around each monitoring station (MS). This method of calculating dose rate increase (DRI) was successful in reproducing the difference in the shape of the DRI decrease due to differences in the initial 214 Bi/ 214 Pb. The estimated concentration exhibited differences among the MSs despite uniform depositions. This difference was considered to have been caused by surface run-off and infiltration of radionuclides.

Realization of radioactive equilibrium in the KRISS radon chamber

The maintenance of radioactive equilibrium between radon and its decay products in a radon chamber is necessary to calibrate radon decay product monitors. In this study, the activity concentrations of radon decay products have been measured, and mosquito-repellent incense has been used to produce aerosol particles in the chamber. Filter papers with 8 μm pore size were used to collect aerosol in the chamber. The activity concentrations of radon decay products have been evaluated by the Modified Tsivoglou Method. The correction factors due to the differences in counting time requirements of the Modified Tsivoglou Method and the time delay between consecutive measurements have been determined. Finally, the radioactive equilibrium has been confirmed by applying the Bateman equation.

Variation of activity concentration of radon decay products in the Curonian Spit

Variation of radon decay products activity concentration on the ground level of the atmosphere has been researched in the Curonian Spit. The influence of meteorological parameters on variation in these pollutants has been estimated. During the measurement period, activities concentration of radon short-lived decay products varied from 2 to 16 Bq/m3 and values of activity concentration measured during day and night varied from 5 to 7 times. The investigation data showed that meteorological parameters as temperature, relative humidity, wind speed and direction had great influence on radon decay products activity concentration. Negative corelation (–0.77) between radon decay products activity concentration and the temperature and positive correlation (0.8) with the relative humidity was determined. It has been observed that variations of activity concentration of radon decay products were influenced by the periodically varying wind direction – breeze, a phenomenon which rarely occurs in the region of the Baltic Sea.

Variation in ozone concentration and volumetric activities of radon progeny on the Curonian Spit

This paper presents the study of variation in ozone concentration and volumetric activities of radon decay products as well as their relationship at the ground level of the atmosphere on the Curonian Spit. The simulta neous measurements of the ground-level ozone concentration and volumetric activity of radon progeny gave a possibility to identify the presence of a breeze phenomenon on the Curonian Spit during an extreme weather event in summer when ozone concentration exceeded the target value of 120 µg m −3 that can have a negative impact on human health. The evident influence of wind direction on ozone concentration and volumetric ac tivity of radon progeny was estimated.

Variation in ozone concentration and volumetric activities of radon progeny on the Curonian Spit

This paper presents the study of variation in ozone concentration and volumetric activities of radon decay products as well as their relationship at the ground level of the atmosphere on the Curonian Spit. The simultaneous measurements of the ground-level ozone concentration and volumetric activity of radon progeny gave a possibility to identify the presence of a breeze phenomenon on the Curonian Spit during an extreme weather event in summer when ozone concentration exceeded the target value of 120 µg m−3 that can have a negative impact on human health. The evident influence of wind direction on ozone concentration and volumetric activity of radon progeny was estimated.

Evaluating the potential alpha energy of radon progeny

Potential alpha energy concentration of radon progeny can be measured using the alpha-spectroscopy with the silicon semiconductors detectors and the gross-counting attached with the ZnS detectors. The decay method was applied where the alpha particles emitted from the 218Po to 214Po were detected. In the case of the decay products, the amount and aerodynamic behavior of radioactivity are important, and also need to be measured. During the experiment, the radon gas was supplied and evaluated from the experimental room with constant concentration. Then the air sample was used as the known volume and the grab sampling technique was developed for estimating the concentration of radon decay products. However the proper calculation was applied for estimating the potential alpha energy of radon progeny through of 218Po, 214Pb and 214Bi.

Mitigation of thoron exposure by application of wallpaper as a diffusion barrier

Increasing attention has been paid in recent years to the radioactive gas thoron ((220)Rn), which can cause a significant exposure and increase of lung cancer risk in some regions worldwide. Some experiments were designed to examine whether different types of wall decoration in the room, from ordinary newsprint to commercial wallpaper, can mitigate the concentrations of indoor thoron decay products. Decoration with coated paper was very effective in decreasing the thoron decay products concentration, thus reducing the effective dose by 90 %, while newsprint decoration, which is common in many rural parts of the world, was found to have a smaller but still significant effect in reducing the thoron decay products concentration when applied to the same house.

Mitigation of radon and thoron decay products by filtration

Inhalation of indoor radon ( 222Rn) and thoron ( 220Rn) decay products is the most important source of exposure to ionizing radiation for the human respiratory tract. Decreasing ventilation rates due to energy saving reasons in new buildings suggest additional active mitigation techniques to reduce the exposure in homes with high radon and thoron concentrations but poor ventilation. Filtration techniques with HEPA filters and simple surgical mask material have been tested for their potential to reduce the indoor exposure in terms of the total effective dose for mixed radon and thoron indoor atmospheres. The tests were performed inside an experimental room providing stable conditions. Filtration (at filtration rates of 0.2 h −1 and larger) removes attached radon and thoron decay products effectively but indoor aerosol as well. Therefore the concentration of unattached decay products (which have a higher dose coefficient) may increase. The decrease of the attached decay product concentrations could be theoretically described by a slowly decreasing exponential process. For attached radon decay products, it exhibited a faster but weaker removal process compared to attached thoron decay products (− 70% for attached radon decay products and − 80% for attached thoron decay products at a filtration rate of 0.5 h −1 with an HEPA filter). The concentration of unattached thoron decay products increased distinctly during the filtration process (+ 300%) while that of unattached radon decay products rose only slightly though at a much higher level (+ 17%). In the theoretical description these observed differences could be attributed to the different half-lives of the nuclides. Considering both effects, reduced attached and increased unattached decay product concentrations, filtration could significantly decrease the total effective dose from thoron whereas the overall effect on radon dose is small. A permanent filtration is recommended because of the slow decrease of the thoron decay product concentrations.

A setup for monitoring radon in air by aerosol filters

A new method for monitoring radon concentrations in air, which is based on measuring the γ activity of aerosol filters, through which air is uninterruptedly circulated, is described. In this case, the equilibrium concentration of decay products on the filter is proportional to the radon concentration in air. The use of a large (20 (diameter) - 20 cm) NaI(Tl) crystal with a well for realizing a 4π-geometry ensures a 15-to 20% error of the method.

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.

Radioactive and stable elements’ concentration in medicinal plants from Brazil

Since the early days of mankind, plants have been used as food and for medicinal purposes. Still, little information exists in literature about the activity concentration of 238U and 232Th decay products, as well as stable element concentrations in Brazilian plants. Activity concentrations of 226Ra, 228Ra and 210Pb, and chemical concentrations of As, Ba, Br, Cs, Co, Cr, Cu, Eu, Fe, Hf, La, Lu, Rb, Sb, Sc, Sm, Ta, Tb, Yb, Zn and Zr were determined in ten samples commonly used in Brazilian medicinal plants.

Verification of a Fissile Material Cutoff Treaty: The case of enrichment facilities and the role of ultra-trace level isotope ratio analysis

One challenge to a potential verification regime for a Fissile Material Cutoff Treaty (FMCT) would be to assure that enrichment plants are not producing highly enriched uranium (HEU) for weapons purposes. Namely in some older enrichment plants, operated in nuclear weapon states, environmental sampling techniques might detect particles from historic HEU production. Determination of the age of these particles would be the most direct confirmation of treaty-compliance. While methods are available to determine the age of nuclear materials based on the concentrations of decay products, micron-sized uranium particles are particularly difficult to analyze. We will review the sensitivity requirements for age determination of HEU particles in an FMCT, and assess the potential of advanced measurement techniques available for this application.

UNCERTAINTY AND VARIABILITY IN HISTORICAL TIME-WEIGHTED AVERAGE EXPOSURE DATA

Beginning around 1940, private companies began processing of uranium and thorium ore, compounds, and metals for the Manhattan Engineer District and later the U.S. Atomic Energy Commission (AEC). Personnel from the AEC's Health and Safety Laboratory (HASL) visited many of the plants to assess worker exposures to radiation and radioactive materials. They developed a time-and-task approach to estimating "daily weighted average" (DWA) concentrations of airborne uranium, thorium, radon, and radon decay products. While short-term exposures greater than 10(5) dpm m(-3) of uranium and greater than 10(5) pCi L(-1) of radon were observed, DWA concentrations were much lower. The HASL-reported DWA values may be used as inputs for dose reconstruction in support of compensation decisions, but they have no numerical uncertainties associated with them. In this work, Monte Carlo methods are used retrospectively to assess the uncertainty and variability in the DWA values for 63 job titles from five different facilities that processed U, U ore, Th, or 226Ra-222Rn between 1948 and 1955. Most groups of repeated air samples are well described by lognormal distributions. Combining samples associated with different tasks often results in a reduction of the geometric standard deviation (GSD) of the DWA to less than those GSD values typical of individual tasks. Results support the assumption of a GSD value of 5 when information on uncertainty in DWA exposures is unavailable. Blunders involving arithmetic, transposition, and transcription are found in many of the HASL reports. In 5 out of the 63 cases, these mistakes result in overestimates of DWA values by a factor of 2 to 2.5, and in 2 cases DWA values are underestimated by factors of 3 to 10.

Nanosize radon short-lived decay products in the air of the Postojna Cave

At two points in the Postojna Cave, short-term monitoring in summer and in winter of air concentrations of radon and radon decay products, equilibrium factor, unattached fraction of radon decay products ( f un), barometric pressure, relative air humidity in the cave and air temperature in the cave and outdoor has been carried out, with the emphasis on f un. Dose conversion factors, calculated on the basis of f un values obtained (ranging from 0.09 to 0.65) exceed 5 mSv WLM − 1 , by a factor of 11.5–14.0 in summer and of 3.0–4.0 in winter for mouth breathing, and 3.1–3.5 in summer and 1.5–1.7 in winter for nasal breathing.

Radon gas distribution in natural gas processing facilities and workplace air environment

Evaluation was made of the distribution of radon gas and radiation exposure rates in the four main natural gas treatment facilities in Syria. The results showed that radiation exposure rates at contact of all equipment were within the natural levels (0.09–0.1 μSv h −1) except for the reflex pumps where a dose rate value of 3 μSv h −1 was recorded. Radon concentrations in Syrian natural gas varied between 15.4 Bq m −3 and 1141 Bq m −3; natural gas associated with oil production was found to contain higher concentrations than the non-associated natural gas. In addition, radon concentrations were higher in the central processing facilities than the wellheads; these high levels are due to pressurizing and concentrating processes that enhance radon gas and its decay products. Moreover, the lowest 222Rn concentration was in the natural gas fraction used for producing sulfur; a value of 80 Bq m −3 was observed. On the other hand, maximum radon gas and its decay product concentrations in workplace air environments were found to be relatively high in the gas analysis laboratories; a value of 458 Bq m −3 was observed. However, all reported levels in the workplaces in the four main stations were below the action level set by IAEA for chronic exposure situations involving radon, which is 1000 Bq m −3.

Nano-size radon short-lived progeny aerosols in Slovenian kindergartens in wintertime

Indoor air concentrations of radon and radon short-lived decay products, equilibrium factors, unattached fractions of radon short-lived decay products ( f un), relative humidity, and temperature have been measured in 29 rooms of 13 Slovenian kindergartens, with an emphasis on f un as a crucial parameter in dose assessment. Dose conversion factors, based on the measured f un values were compared to epidemiology-based value of 5 mSv WLM −1.

The Influence of the Concentration of Atmospheric Radon Decay Products on the Environmental Radiation Dose Rate

It has been occasionally found from an area monitoring data obtained at an atomic power station that the daily periodical change of the environmental radiation dose rate appeared near the ground surface. It is suggested that the variation has resulted from the change of atmospheric radon concentration and that it has also depended on the geographical features of the observation point. The change component has been estimated to be up to nearly 30 percent of the environmental radiation dose rate from monitoring data. To investigate precisely the phenomena, observation was performed near a monitoring station and at other area in Fukui Prefecture during the summer. The dose rate from terrestrial radiation was 42nGy/h at the Natasho in Ooi Town and was 30nGy/h at the Kaminaka in Wakasa Town. The concentration of radon decay products in the air was 0.5-30Bq/m3 at the Natasho site and was 1-10Bq/m3 at the Kaminaka site. From the concentration of radon decay products in the atmosphere, the dose rate was respectively estimated to be 0-7.0nGy/h at the Natasho site, and to be 0-5.5nGy/h at the Kaminaka site. Furthermore, 0.26 (nGy/h)/(Bq/m3) and 0.56(nGy/h)/(Bq/m3) were estimated as the dose rate conversion factor of radon concentration in the air at the Natasho site and at the Kaminaka site, respectively.

Effective doses in schools based on nanosize radon progeny aerosols

Indoor air concentrations of radon and radon short-lived decay products, equilibrium factors, unattached fractions of radon short-lived decay products ( f un), relative humidity and temperature have been measured in Slovenian schools, with an emphasis on f un as the crucial parameter in dose assessment. The following geometric mean and geometric standard deviation values, respectively, were obtained: C Rn: 700 Bq m −3 and 3.29; C RnDP: 441 Bq m −3 and 3.07; F: 0.59 and 1.30; and f un: 0.12 and 1.43. Dose conversion factors, based on the measured f un values were compared to epidemiology based value of 5 mSv/WLM.

A study of indoor 220rn and 222rn decay product concentrations in the uk

In order to gain a better understanding of the risk of human exposure to 220Rn indoors, measurements of 220Rn decay products have been performed in a number of houses in England. The study focused mainly on areas where above-average indoor 220Rn concentrations were to be expected because of geological or other factors. Thoron (220Rn) in room air comes mainly from the building materials, with an additional contribution from soil gas; therefore, 220Rn concentrations were examined in relation to building materials as well as location. Measurements were carried out in 23 houses. The mean equilibrium equivalent 220Rn (EET) concentration found was 0.39 Bq m-3 and the mean equilibrium equivalent 222Rn (EER) concentration was 17.8 Bq m-3. The 220Rn concentration values and EET/EER ratios found in this investigation correspond well with other published results. Values imply that the 220Rn concentrations in English dwellings are a far less important problem than 222Rn concentrations.

An intercomparison between gross α counting and gross β counting for grab-sampling determination of airborne radon progeny and thoron progeny

The instantaneous values of the airborne activity concentrations of radon progeny and thoron progeny have been determined 34 times in a closed and windowless room in a cellar using two independent grab-sampling methods in order to compare the performance of the methods. The activity concentration of radon ( 222Rn) was also measured and it varied between 200 and 650 Bq m −3. Two samples of radon and thoron progeny were collected simultaneously from roughly the same air volume by filtering. For the first method, the isotopes were collected on membrane filter and gross α counting was applied over several successive time intervals. This method was a slightly improved version of the methods that are applied generally for this reason for decades. For the second method, the isotopes were collected on glass-fibre filter and gross β counts were registered over several time intervals. This other method was developed a few years ago and the above series of measurements was the first opportunity to make an intercomparison between it and another similar method based on α counting. Individual radon progeny and thoron progeny activity concentrations (for the isotopes 218Po, 214Pb, 214Bi and 212Pb) were evaluated by both methods. The detailed investigation of the results showed that the systematic deviation of the methods is small but significant and isotope-dependent. The weighted averages of the β/α activity concentration ratios for 218Po, 214Pb, 214Bi, EEDC 222 (Equilibrium-Equivalent Decay-product Concentration of radon progeny) and 212Pb were 0.99±0.03, 0.90±0.02, 1.03±0.02, 0.96±0.02 and 0.80±0.03, respectively. The source of the systematic deviation is probably the inaccurate knowledge of the counting efficiencies mainly in the case of the α-counting method. A significant random-type difference between the results obtained with the two methods has also been revealed. For example, the β/α ratio for EEDC 222 varied between 0.81±0.01 and 1.22±0.03, where the errors derive from the random errors of the independent β and α results. The detailed investigation of the results showed that the α method is responsible for the overwhelming part of this random deviation that was caused mainly by the lower accuracy, stability and reliability of this method. The performance of the β method proved to be better mainly because of its higher accuracy, stability and reliability.