Mitigation effects of radon decay products by air cleaner

One of the most effective methods for reducing exposure is the use of air cleaners. In this study, a dose mitigation of a commonly-used Japanese air cleaner under conditions in which aerosols are continuously supplied was investigated. Although the values of the EERC during an operation of air cleaner decreased, values of the f _p increased with the use of air cleaner. An effective dose was calculated on the basis of our experimental results, resulting in the dose mitigation of about 40 % by the air cleaner. Air cleaners can be regarded as an effective tool for the dose mitigation under with conditions in which aerosols are continuously supplied.     

Measurements of radon,thoron and their progeny in Gifu prefecture,Japan

Summary Due to the rocky neighborhood, consisting of mostly granite with high radium content, an elevated radon concentration was found in a territory of Gifu prefecture situated in the middle of Japan. Radon concentrations in water were measured and were found to be considerably high. Since indoor radon and radon progeny concentrations might be relatively high, their concentrations were also analyzed. Besides the radon and radon progeny, thoron and thoron progeny concentrations were also investigated. Dose estimations for radon and thoron in indoor air are discussed.     

Superheavy nuclei and hypernuclei: extending the limits of the nuclear chart

In this study, a tubular radon removal device and a movable one were prepared and investigated. The tubular radon removal device in an air conditioning return air system reduced the radon progeny by more than 84%. The radon progeny concentration reached equilibrium after 4 h when it was used only for a ventilation at the rate of 10 h⁻¹. Radon progeny removal efficiency was above 95% for the movable radon removal device, when the ventilation rate was 17 h⁻¹. The results showed that the radon removal devices can effectively remove the radon progeny in the air.

     

Concentrations of radon,thoron and their decay products measured in natural caves and ancient mines by using solid state nuclear track detectors and resulting radiation dose to the members of the public

Alpha- and beta-activities per unit volume of air due to radon (²²²Rn), thoron (²²⁰Rn) and their progenies were measured in the air of natural caves and ancient mines as well as inside different reference atmospheres by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). In addition, the radon concentration was continuously measured inside one of the studied caves by using the SSNTDs’ method and AlphaGuard counter. Equilibrium factors between radon and its daughters and between thoron and its progeny were evaluated in the studied atmospheres. Alpha-activities due to ²¹⁸Po and ²¹⁴Po short-lived radon decay products were determined in different compartments of the respiratory tract of members of the public. The committed equivalent doses due to the ²¹⁸Po and ²¹⁴Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of the visitors of the considered caves and ancient mines. Annual effective doses due to radon progeny from the inhalation of air by the visitors of the studied caves and ancient mines were evaluated.     

Radon and thoron progeny levels in air samples at Udagamandalam region of Nilgiris in India

Measurement of concentration of radon and thoron daughter products in various indoor environment covering four seasons of a year in Udagamandalam Taluk of Nilgiris biosphere has been carried out using a high volume air sampler to asses the inhalation dose to the population which delivers higher dose than the radon and thoron gas alone. The potential alpha-energy concentrations of the radon and thoron progeny ranged from 0.97 to 12.72 mWL and from 1.63 to 15.83 mWL with a geometric mean of 6.02 and 7.89 mWL, respectively, taking all seasons into account. These measurements have yielded a wealth of data on the variation among the indoor radon and thoron progeny in various places during different seasons. The radon and thoron progeny levels are higher in winter seasons and are less in summer season with autumn and spring data lie in between winter and summer. Using the dose conversion factor for indoor exposures given in UNSCEAR 93 report the internal equivalent dose to the inhalation of radon progeny is evaluated to be 1357 mSv^.y^–1 and the corresponding annual effective dose equivalent value has been found to be 2.13 mSv^.y^–1. It can be observed that the mean value of radon is higher than the Indian average. Also it is found the radon and thoron progeny levels are higher in the case of houses built with rock and granite and in tiled type houses of nearly 100 years old. The levels are less in the case of houses built with brick and cement. The observed results for different types of houses and seasons are discussed in this paper.     

A method for the mg scale separation of curium(III) from americium(III) by HPLC using a SCX column

Radon, thoron and their progeny are responsible for more than 50% of the total ionizing radiation dose received by human population. In the present work, radon, thoron and their progeny concentration measurements have been carried out in 150 dwellings in different villages of Faridabad district of Haryana, India. Pin-holes based twin cup dosimeter containing LR-115 type-II film (solid state nuclear track detectors) has been used for the time-integrated passive measurement of radon and thoron concentrations. The dosimeters were deployed for three seasons each having 4 months of exposure period. For measurement of radon and thoron progeny concentration (EERC/EETC), deposition based direct radon/thoron progeny sensors (DRPS/DTPS) were deployed with dosimeters. Based on the gamma exposure rate in different villages during preliminary survey and type of houses available in the regions, numbers of dwellings of different categories have been selected. Radon, thoron and their progeny concentration and total annual effective inhalation dose were calculated and compared with the recommended limits by UNSCEAR, ICRP and WHO.

     

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.     

Characterization of airborne radon released by domestic showering and the use of a washing machine

Water originated from groundwater systems can have relatively high concentration of radon. In many situations, radon is released from the water and mixes with the indoor air. In the present study, laboratory experiments were conducted to characterize the airborne radon released by showering and the use of a washing machine. The followings were discussed: (1) a comparison between the loss of waterborne radon and the increase of airborne radon, (2) time-related changes in airborne radon after the water use, (3) changes in the equilibrium factor, and (4) the relationship between radon concentration and the distance from the source of radon release.     

Study of radon,thoron and their progeny levels in indoor environment of Firozabad city in U.P., India

Twin cup pin-hole dosimeters having LR-115 as the detector were used to measure the concentration of radon and thoron in the dwellings of Firozabad city of Uttar Pradesh State in India. The mean values of radon, thoron, radon progeny and thoron progeny concentrations were found to be 37.4 Bqm^?3, 13.7 Bqm^?3, 4.0 and 1.5 mWL respectively. The average value of annual effective dose equivalent to the inhabitants of Firozabad city was found to be 1.1 mSv and is below the action level as recommended by the ICRP.     

Continuous measurements of radon and radon progeny as a basis for management of radon as a hazard in a tourist cave

A six month survey of radon, radon progeny and condensation nuclei (CN) has been conducted in an Australian tourist cave. The measurements have been made continuously at two sites within the cave: one a small chamber with a high air exchange rate close to one entrance and connected to several other entrances by complex passages; the other a large chamber with a low air exchange rate 1 km from the nearest entrance. The measurements form a basis for evaluation of the accuracy with which dose due to radon can be determined for different monitoring strategies. It is shown that the estimate of dose based on the measurement of radon concentration and recommendations in ICPR-65, is low by a factor of 1.3 at the well ventilated site and 1.5 at the site with a low air exchange rate and low CN. At each site the weekly average equilibrium factor and unattached fraction were steady, leading to the possibility of establishing a cave system average of these factors. However, given the technical diffuculties involved, it may not be practicable to make enough unattached fraction measurements to fully represent the cave system. Therefore it may be necessary to use a conservative approach to the dosimetry and add 50% to values determined by the ICRP-65 conversion convention.     

Assessment of radon concentration and external gamma radiation level in the environs of Narwapahar uranium mine,India and its radiological significance

In the environs of uranium mining, milling and processing facilities and in the uranium mineralized terrain, a little higher ambient radon concentration and gamma radiation level may be expected in comparison with natural background. The present study gives a brief account of atmospheric radon concentration, gamma absorbed dose rate and radiation dose received by the members of public in the vicinity of Narwapahar uranium mine. The ambient radon concentration in the air in the study area was found to vary from 5 to 107 Bq m⁻³ with geometric mean of 24 Bq m⁻³ and geometric standard deviation of 1.74 Bq m⁻³. The measured gamma absorbed dose rate in air at 1 m above the ground ranged from 87 to 220 nGy h⁻¹ with an overall arithmetic mean of 128 ± 18.5 nGy h⁻¹. The mean annual effective dose received by the members of public from inhalation of radon and its progeny and external gamma exposure was estimated to be 0.32 mSv year⁻¹, which is comparable to other reported values elsewhere.     

Influence of the building material and ventilation rate on the concentration of radon, thoron and their progenies in dwelling rooms using SSNTD and Monte Carlo simulation

A new Monte Carlo computer code was developed for determining the detection efficiencies of the CR-39 and LR-115 II solid state nuclear track detectors (SSNTD) for a-particles emitted by radon (²²²Rn) and thoron (²²⁰Rn) series inside the atmosphere of dwelling rooms. Alpha-activities due to radon, thoron and their decay products, were evaluated for the determination of the detection efficiencies of the SSNTD utilized for the emitted a-particles by measuring the corresponding track densities. The influence of the ventilation rate and building material on the concentration of radon, thoron and their progenies was investigated. Equilibrium factors between radon and its progeny and between thoron and its daughters have been evaluated in the air of the rooms.     

Measurement of radon and thoron progeny size distributions and dose assessments at the mineral treatment industry in Thailand

A new portable type cascade impactor has been developed to determine the activity size distribution of radon and thoron progeny in a natural environment more efficiently. The modified impactor consists of 4 stages with a back up filter stage for the collection of aerosol samples. The aerosol cut points in the impactor are set for 10, 2.5, 1 and 0.5 μm at a flow rate of 4 L min^?1. Five CR-39 chips were used as alpha detectors for each stage. In order to separate α particles emitted from radon and thoron progeny, CR-39 detectors are covered with aluminum-vaporized Mylar films. The thickness of each film is adjusted to allow α particles emitted from radon and thoron progeny to reach the CR-39 detectors. The technique has been successfully tested in field studies, particularly inside a mineral treatment industry in Thailand to estimate doses in the working environment. The dose calculations by lung dose evaluation program showed that activity median aerodynamic diameters played a significant role in determining the particle size distributions of the attached radon and thoron progeny. The dose conversion factor determined from short term measurements due to exposure from the inhalation of thoron and its progeny was found to be 4 times higher than comparable values for radon and its progeny. The effective dose for workers exposed to radon is about 4–6 times higher than thoron.     

Modeling of the radon exhalation from water to air by a hybrid electrical circuit

A new model based on electric circuit theory has been introduced for modeling the radon exhalation from water to air in a sample bottle. Comparing the differential equations for radon exhalation from water to air and a hybrid electrical circuit shown that the volume of water or air, radon concentration, radon flux and solubility coefficient (dependent on temperature of water) are equivalent with capacitance, voltage across of capacitor, current and voltage gain, respectively. Then by using a hybrid electrical model total radon transfer velocity from water to air and time variation of water radon concentration in our experimental setup has been obtained. Also the variations of air radon concentration with temperature, volume of water and volume of air is obtained. The results show a good agreement with those in literatures.     

Absolute Determination of Radon in me Marine Troposphere

Abstract

A method for the direct determination of radon in the atmosphere was developed to measure radon mixing ratio with high precision at the low levels found in the marine troposphere away from continental air mass contamination. Developed for the DYCOMS atmospheric dynamic and chemical measurement experiment over the eastern Pacific Ocean during July and August, l985 it combines scintillation cell counting with the collection of large volume air samples using low flying aircraft. An equation that combines the growth and decay of radon and radon progeny was written for a microcomputer and is used to compare alpha activity in the cell with the number of radon atoms in a sample. Radon mixing ratios as low as 12 atoms per liter of air have been measured using this method.     

Field measurement of the <Superscript>218</Superscript>Po, <Superscript>214</Superscript>Pb and <Superscript>214</Superscript>Bi concentrations in typical indoor and outdoor environments in Beijing

The activity concentrations of ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi [i.e. C(²¹⁸Po), C(²¹⁴Pb), and C(²¹⁴Bi)] and the calculated concentration ratios [i.e. 1:C(²¹⁴Pb)/C(²¹⁸Po):C(²¹⁴Bi)/C(²¹⁸Po)] are necessary for assessing radon and its progenies exposure. In this study, a measurement method of radon progenies concentrations with both high sensitivity and low uncertainty, was developed based on the Kerr method. The field measurement results of radon progeny concentrations and calculated concentration ratios in both typical indoor and outdoor environments in Beijing, China, were reported. The effects of air exchange rate on concentration ratios of radon progenies in indoor environments were discussed.     

Radon concentration of outdoor air: measured by an ionization chamber for radioisotope monitoring system at radioisotope institute

Gas-flow ionization chambers for radioisotope (RI) monitoring systems at RI institutes throughout Japan are commonly used to measure RIs which leak from the RI institutes. Before the Japan’s 2011 Tohoku earthquake [11 March 2011, moment magnitude (M _w) 9.0], ionization current data measured with a gas-flow ionization chamber at the RI institute of Fukushima Medical University were found to change. The question we must raise is whether the variation ionization current can be considered to the variation of outdoor radon concentration. The conversion factors (from ionization current to radon concentration in air) of the gas-flow ionization chamber can be obtained by measuring four levels of radon concentration (outdoor air, indoor air, high level and radon-free gas) with an AlphaGUARD monitor and the chamber itself. The two gas-flow ionization chambers consist of the air intake and terminal exhaust duct of the RI institute. It was found that the radon concentration in the exhaust air was the same as that in the air intake. This study provided evidence that variations of outdoor radon concentration could be determined using gas-flow ionization chambers for RI monitoring systems.     

Determination of plutonium in ground-level air aerosols collected on Petrianov filters

Determination of plutonium in air filters as modification of the procedure applied to soil samples is presented. The Petrianov filter with collected air aerosol and dust was submitted to direct leaching with 6M HCl. Co-precipitation with Fe(OH)₃ and calcium oxalate, anion exchange separation and electrodeposition, and finally alpha spectrometry was used to determine the plutonium concentration in the samples. Mean activity of ^239,240Pu in the air was 9.1 nBq/m³ (in 1998 and 1999). The problem of the radon progeny, ²¹⁰Po, appearing on the alpha plutonium spectra is discussed. The correlation of plutonium concentration with mass of the collected dust was better than with an air volume passed through the filter.     

Investigation of radon and thoron concentrations in a landmark skyscraper in Tokyo

The temporal variation of the radon concentration, and the radon and thoron concentrations every 3 months for a year were measured using two types of devices in a landmark skyscraper, the Tokyo Metropolitan Government Daiichi Building. In the measurement of temporal variation of the radon concentration using a pulse type ionization chamber, the average radon concentration was 21 ± 13 Bq m^?3 (2–68 Bq m^?3). The measured indoor radon concentration had a strong relationship with the operation of the mechanical ventilation system and the activities of the office workers. The radon concentration also increased together with temperature. Other environmental parameters, such as air pressure and relative humidity, were not related to the radon concentration. In the long-term measurements using a passive radon and thoron discriminative monitor, no seasonal variation was observed. The annual average concentrations of radon and thoron were 16 ± 8 and 16 ± 7 Bq m^?3, respectively. There was also no relationship between the two concentrations. The annual average effective dose for office workers in this skyscraper was estimated to be 0.08 mSv y^?1 for 2000 working hours per year. When considering the indoor radon exposure received from their residential dwellings using the annual mean radon concentration indoors in Japan (15.5 Bq m^?3), the annual average effective dose was estimated to be 0.37 mSv y^?1. This value was 31 % of the worldwide average annual effective dose.     

Rapid determination of radon progeny concentration based on artificial neural networks

Journal of Radioanalytical and Nuclear Chemistry - The rapid measurement of radon progeny concentration is of great significance for improving the efficiency of radon exposure dose evaluation in a...