Radon, thoron and their progenies measured in different dwelling rooms and reference atmospheres by using CR-39 and LR-115 SSNTD.

Detection efficiencies of the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD) for alpha-particles emitted by radon, thoron and their decay products inside the air of different dwelling rooms and in various reference atmospheres were determined by using a Monte Carlo computer code. Alpha- and beta-activities per unit volume of air due to radon, thoron and their progenies were measured in the studied atmospheres by exploiting data obtained for the detection efficiencies of the SSNTD and measuring the resulting track density rates. Equilibrium factors between radon and its progeny and thoron and its daughters were evaluated in the studied atmospheres.     

Use of three new SSNTD methods for evaluating thorium contents in different building materials and measuring thoron and its progeny concentrations inside dwellings.

Three new methods based on using CR-39 and LR- 115 type II solid state nuclear track detectors (SSNTD) were used for measuring thorium concentrations (in 10(-6)g/g (ppm)) inside different building materials and evaluating the resulting concentrations of thoron and its progenies in dwellings built by the studied materials. The first technique consists of determining the probabilities for alpha-particles emitted by the uranium and thorium series inside the building materials or by the radon and thoron groups inside the dwelling atmosphere to reach and be registered as tracks on the SSNTD utilized and exploiting the resulting track density rates. The second method consists of evaluating the mean critical angles of etching of the CR-39 and LR-115 II SSNTD and measuring the resulting track densities registered on the detectors utilized. The third technique is based on calculating the detection efficiencies of the CR-39 and LR-115 II SSNTD for a-particles emitted by the uranium and thorium series in the building materials or by the radon and thoron groups in air and measuring track density rates registered on these detectors. The influence of the building material's nature and ventilation rate on the thoron and its decay products inside the dwelling rooms studied has been investigated.     

Characterization of the Oum Er Rbia (Morocco) high basin karstic water sources by using solid state nuclear track detectors and radon as a natural tracer

Uranium and thorium contents as well as radon -activities per unit volume were evaluated inside different water samples by using a method based on calculating the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs) detection efficiencies for the emitted -particles and measuring the resulting track density rates. The validity of the SSNTD technique utilized was checked by analysing uranyl nitrate (UO₂(NO₃)₂6H₂O) standard solutions. A relationship between water radon concentration and water transmission of different water sources belonging to two regions of the Middle Atlas (Morocco) water reservoir was found. The influence of the water flow rate as well as the permeability and fracture system of the host rocks of the sources studied was investigated.     

Comparison between different methodologies for detecting radon in soil along an active fault: The case of the Pernicana fault system,Mt. Etna (Italy)

Three different methodologies were used to measure Radon (²²²Rn) in soil, based on both passive and active detection system. The first technique consisted of solid-state nuclear track detectors (SSNTD), CR-39 type, and allowed integrated measurements. The second one consisted of a portable device for short time measurements. The last consisted of a continuous measurement device for extended monitoring, placed in selected sites. Soil ²²²Rn activity was measured together with soil Thoron (²²⁰Rn) and soil carbon dioxide (CO₂) efflux, and it was compared with the content of radionuclides in the rocks. Two different soil–gas horizontal transects were investigated across the Pernicana fault system (NE flank of Mount Etna), from November 2006 to April 2007. The results obtained with the three methodologies are in a general agreement with each other and reflect the tectonic settings of the investigated study area. The lowest ²²²Rn values were recorded just on the fault plane, and relatively higher values were recorded a few tens of meters from the fault axis on both of its sides. This pattern could be explained as a dilution effect resulting from high rates of soil CO₂ efflux. Time variations of ²²²Rn activity were mostly linked to atmospheric influences, whereas no significant correlation with the volcanic activity was observed. In order to further investigate regional radon distributions, spot measurements were made to identify sites having high Rn emissions that could subsequently be monitored for temporal radon variations. SSNTD measurements allow for extended-duration monitoring of a relatively large number of sites, although with some loss of temporal resolution due to their long integration time. Continuous monitoring probes are optimal for detailed time monitoring, but because of their expense, they can best be used to complement the information acquired with SSNTD in a network of monitored sites.     

Measurements of the half-life of 214Po and 218Rn using digital electronics

The half-lives of (214)Po and (218)Rn have been measured. The radionuclides were produced in the decay of a (230)U source and the emitted alpha-particles were measured in nearly-2π geometry with an ion-implanted planar silicon detector. The data acquisition was performed with a digitiser operated in list mode, saving the energy and time of detection (10 ns precision timestamp) of each event. The half-lives were deduced from the time differences between the alpha-decays populating the nuclide of interest and those corresponding to its decay. Different methods were applied, based on delayed coincidence counting and time-interval distribution analysis. The resulting half-lives are 33.75 (15) ms for (218)Rn and 164.2 (6) μs for (214)Po, both in agreement with some of the literature values, and obtained with higher precision in this work.     

High-resolution alpha-particle spectrometry of the 230U decay series

High-resolution alpha-particle spectrometry was performed on the (230)U decay series. A (230)U source was prepared on a stainless steel disc by electrodeposition in an ammonium nitrate solution. Spectrometry of the alpha-particle energy spectrum was performed with ion-implanted planar silicon detectors in vacuum. A set of alpha emission probabilities is presented for (230)U and (226)Th. The measured peak intensities were corrected mathematically for coincidental detection of alpha-particles and conversion electrons emitted in the same decay. A good agreement with literature data was observed. The uncertainty budget and the correlation matrix are presented. The validity of the alpha-particle energies was tested and could be confirmed for most peaks within a few keV, but discrepancies were found for the 2nd peak of (226)Th and the main peak of (218)Rn.     

Impact of fluoride and other aquatic parameters on radon concentration in natural waters.

Radon (222Rn) accumulation in water in relation to stable elements was studied for the purpose of determining factors influencing the transfer of 222Rn to and from water. In 72 groundwater samples, 222Rn and about 70 analytical parameters were analysed using radiometric and ICP-MS techniques. Using multivariate statistics (partial least squares), it was observed that 222Rn has a positive correlation with fluoride and uranium. The correlation with fluoride was further investigated by a laboratory time-scale experiment to measure the emanation of 222Rn from water as a function of fluoride, pH and carbonate. The transfer of 222Rn from water was measured by continuous monitoring in air in a closed loop set-up. It was observed that fluoride in water adhere or trap 222Rn preferably in acidic water (pH 3). It is suspected that natural physical processes (such as diffusion and microbubble phenomenon) are less effective to transport 222Rn in the presence of fluoride.     

Natural radioactivity and radon exhalation rate of soil in southern Egypt

The level of natural radioactivity in soil of 30 mining samples collected from six locations in southern Egypt was measured. Concentrations of radionuclides in samples were determined by γ-ray spectrometer using HPGe detector with a specially designed shield. The obtained results of uranium and thorium series as well as potassium (K-40) are discussed. The present data were compared with data obtained from different areas in Egypt.

Also, a solid state nuclear track detector SSNTD (Cr-39) was used to measure the radon concentration as well as exhalation rate for these samples. The radon concentrations were found to vary from 1.54 to 5.37 Bq/kg. The exhalation rates were found to vary from 338.81 to 1426.47 Bq/m²d. The values of the radon exhalation rate are found to correspond with the uranium concentration values measured by the germanium detector in the corresponding soil samples.     

Radiation effect on positronium formation in solid state nuclear track detector.

The effect of alpha-particles on CR-39, a material used in solid state nuclear track detectors (SSNTDs), has been investigated using the positron annihilation lifetime (PAL) technique. The samples were irradiated using a (238)Pu alpha-source of energy ranging from 1 to 5 MeV and with different doses ranging from 0 to 57.87 mGy. The ortho-positronium (o-Ps) lifetime, tau(3), shows a slight increase as the irradiation dose increases, while a rapid change in the o-Ps intensity, I(3) at 10 mGy was found. In addition, the PAL parameters (tau(3), I(3)) have been studied as a function of the energy of alpha-particles. The obtained results indicate that the o-Ps lifetime increases slightly with increasing energy of the alpha-particle. On the other hand, the o-Ps intensity decreases exponentially with increasing alpha-particle energy, plateaus, and finally increases. The data show that the track diameter increases with decreasing energy of the alpha-particle, while the track density increases with increasing the irradiation dose. A correlation between the track diameter and the o-Ps hole diameter was observed.     

Effect of americium-241 alpha-particles on the dose-response of chromosome aberrations in human lymphocytes analysed by fluorescence in situ hybridization

PURPOSE: To evaluate by the fluorescent in-situ hybridization (FISH) technique the dose-response and intercellular distribution of alpha-particle-induced chromosome aberrations. In particular, the validity of using the yield of characteristic types of chromosome abnormalities in stable cells as quantitative indicators for retrospective dose reconstruction has been evaluated. MATERIAL AND METHODS: Monolayers of human peripheral lymphocytes were exposed at doses from 0.02 to 1 Gy to alpha-particles emitted from a source of americium-241. The most probable energy of the alpha-particles entering the cells was 2.7 MeV. FISH painting was performed using DNA probes for chromosomes 2, 4 and 8 in combination with a pan-centromeric probe. In complete first-division cells, identified by harlequin staining, aberrations involving painted target chromosomal material were recorded as well as aberrations involving only unpainted chromosomal material. RESULTS: In total, the percentage of complex aberrations was about 35% and no dose dependence was observed. When complex-type exchanges were reduced to simple base types, the different cell distributions were clearly over-dispersed, and the linear coefficients of the dose-effect curves for translocations were significantly higher than for dicentrics. For past dose reconstruction, only a few complex aberrations were in stable cells. The linear coefficient obtained for transmissible aberrations in stable cells was more than seven times lower than that obtained in all analysed cells, i.e. including unstable cells. CONCLUSION: FISH-based analysis of complex rearrangements allows discrimination between partial-body exposures to low-linear energy transfer radiation and high-linear energy transfer exposures. In assessing past or chronic exposure to alpha-particles, the use of a dose-effect curve obtained by FISH-based translocation data, which had not excluded data determined in unstable cells, would underestimate the dose. Insertions are ineffective biomarkers because their frequency is too low.     

固体径迹图像分析法测量环境空气中氡浓度的研究

作者利用计算机图像识别技术，建立了测量环境空气中氧浓度测定的固体径迹图像分析方法，并在营房、坑道的氡水平调查中得到了应用．该方法与国家二级计量站标准氡室的比对结果为１０６．８±３．４Ｂｑ·ｍ￣（－３），和后期告知的标准氧暴露量１１５．６±４．３Ｂｑ·ｍ￣（－３），相对误差约为７．６％。测量速度较显微镜目测法有很大的提高，适合环境空气中氡浓度的测定和大规模氡水平调查。     

Response of cultured human airway epithelial cells to X-rays and energetic alpha-particles

Radon and its progeny, which emit alpha-particles during decay, may play an important role in inducing human lung cancer. To gain a better understanding of the biological effects of alpha-particles in human lung we studied the response of cultured human airway epithelial cells to X-rays and monoenergetic helium ions. Our experimental results indicated that the radiation response of primary cultures was similar to that for airway epithelial cells that were transformed with a plasmid containing an origin-defective SV40 virus. The RBE for cell inactivation determined by the ratio of D0 for X-rays to that for 8 MeV helium ions was 1.8-2.2. The cross-section for helium ions, calculated from the D0 value, was about 24 microm 2 for cells of the primary culture. This cross-section is significantly smaller than the average geometric nuclear area (approximately 180 microms 2), suggesting that an average of 7.5 alpha-particles (8 MeV helium ions) per cell nucleus are needed to induce a lethal lesion.     

Performance test for radon measuring instruments using radon chamber at PTB

An intercomparison on radon ((222)Rn) measuring instruments was carried out at the Physikalisch Technische Bundesanstalt, Germany (PTB). Two types of alpha track detectors based on a passive (222)Rn-thoron ((220)Rn) discriminative measurement technique were used: these were the commercially available Raduet and Radopot detectors that were developed and calibrated by the National Institute of Radiological Sciences, Japan (NIRS). The (222)Rn grab sampling and continuous measurement methods were also compared using the PTB pulse ionization chamber. The results using the passive detectors showed that there was a good agreement between the time-integrated (222)Rn concentrations obtained from the Raduet detectors and the PTB pulse ionization chamber, as in the case with the Radopot detectors. In the grab sampling measurements, the agreement between the (222)Rn concentrations measured using the NIRS gas storage ionization chamber and the PTB pulse ionization chamber was within 5% as in the case with the NIRS scintillation cell measurement. Similar to the measurements of the passive detectors and grab sampling, little distinct difference in the (222)Rn concentration was observed for the NIRS continuous electrostatic collection monitor.     

Absorbed fraction of radon progeny in human bronchial airways with bifurcation geometry

PURPOSE: The absorbed fraction, defined as the portion of the initial particle energy which is absorbed in the tissue of interest, was calculated, under bifurcation geometry of the airway tubes, for alpha-particles emitted from radon progeny in the human respiratory tract. The results are given for all branching generations and compared with the data obtained for the commonly used infinite straight cylinders adopted by the International Commission on Radiological Protection (ICRP) Report 66. MATERIALS AND METHODS: A model was created to calculate the absorbed fraction of alpha-particle energy in the human lung using bifurcation geometry. Monte Carlo simulations of alpha-particle propagation in tissue and air were performed. The stopping powers of alpha-particles were adopted from the International Commission of Radiation Units and Measurements (ICRU) Report 49. RESULTS: The absorbed fractions for the bifurcation geometry are given for the 15 generations in the tracheobronchial tree for alpha-particle energies of 6 and 7.69 MeV. The sources were assumed to be the fast and slow moving mucus. CONCLUSIONS: Comparisons with ICRP66 data reveal that the assumption of long, straight cylinders was appropriate in some cases, but not in all. Adoption of the absorbed fractions obtained from the bifurcation model instead of the ICRP66 data caused 'redistribution' of doses in the bronchial (BB) and bronchiolar (bb) regions.     

Inactivation of C3H 10T1/2 cells by monoenergetic high LET alpha-particles.

Inactivation of mouse C3H 10T1/2 cells in plateau-phase (7.8 x 10(4) cells/cm2) was studied by using alpha-particles from the irradiation facility installed for radiobiological experiments at the 3 MV Tandem accelerator, University of Naples. Silicon detectors and CR39 plastic track detectors were employed for dosimetric purposes. The cells were exposed to high LET monoenergetic alpha-particles (energy of 1.8 MeV at the centre of the cell nucleus, track-averaged LET of 177 keV/micron and dose-rate of 1.1 Gy/min) and low-LET 80 kVp X-rays. The X-ray survival curve showed a significant shoulder (alpha/beta = 9 Gy) while the survival curve for alpha-particles was close to exponential. The mean lethal dose of alpha-particles was 0.77 +/- 0.02 Gy and the RBE was 5.2 at 80% survival and 3.0 at 5% survival. Survival of exponentially growing cells (2 x 10(4) cells/cm2) following irradiation with the alpha-particle beam is also reported. The nuclear areas of 10T1/2 cells were measured as 299 +/- 9 micron 2 and 250 +/- 8 micron 2 for cells in log phase and plateau phase, respectively. The inactivation cross-section, obtained from the mean lethal dose, was 34 micron 2 and 37 micron 2 for cells in log phase and plateau phase, respectively. These values appear to be the maximum measured values for the inactivation cross-section of 10T1/2 cells as a function of the alpha-particle LET. This saturation cross-section is very similar to the saturation values reported in the literature for other mammalian cell lines.     

单个α—粒子的细胞效应

为研究生物学上的单粒子效应 ,阐明空间带电粒子生物效应的机理 ,采用一台小型α-放射源微束装置和CN核径迹探测器 ,以双倍体酵母菌作为真核细胞试验体系 ,通过电荷耦合摄像系统 ,得到细胞失活与α-粒子 -细胞碰撞参数之间的关系。结果表明 ,1 .1 3MeV/uα -粒子在细胞 -琼脂混合物中失活范围可达 5.5μm ,大于离子径迹晕半径与酵母细胞半径之和 (约 3 .1 μm)。细胞失活率在 0 .3 6～ 0 .3 3之间。提示 :细胞要由失活到致死 ,需要多次击中 ,然而在未击中情况下 ,失活几率在一定碰撞参数下未必为零。     

The natural radioactivity in Guarani aquifer groundwater, Brazil.

The measurements of gross alpha and gross beta radioactivity in groundwater samples from Guarani aquifer in Brazil are reported in this paper together with the activity concentration of the natural dissolved radionuclides (40)K, (238)U, (234)U, (226)Ra, (222)Rn, (210)Po, (210)Pb, (232)Th, (228Th), and (228)Ra. Most of the gross alpha radioactivity values were below the critical level of detection corresponding to 1mBq/L, however, the whole data set for the gross beta radioactivity and radionuclides (40)K, (238)U, (234)U, (226)Ra, (222)Rn, (210)Po, (210)Pb, and (228)Ra was submitted to a statistical treatment, considering class intervals arranged in geometric progression, because of the great variability of the activity. The analysis indicated lognormal distribution of the data, as usually observed in samples taken from the natural context. An inverse relationship between the gross alpha and gross beta activity has been identified and is related to an increase in the K content in the water. The mobility coefficient has been estimated for (238)U, (226)Ra, (232)Th and (228)Ra in Guarani aquifer and the results indicated that the radioelement solubility in the studied system varies according to the following order: radium>uranium>thorium. The implications of the data obtained in terms of standards established for defining the drinking water quality have also been discussed.     

Yields of SSB and DSB induced in DNA by Al(K) ultrasoft X-rays and alpha-particles: comparison of experimental and simulated yields.

PURPOSE: To compare experimental yields of single strand breaks (SSB) and double strand breaks (DSB) induced in plasmid DNA in aqueous solution by alpha-particles and Al(K) ultrasoft X-rays (USX) with the corresponding yields, generated via computer simulations, for a range of mean diffusion distances of the hydroxyl radical (*OH). MATERIALS AND METHODS: Aerobic, aqueous solutions of plasmid DNA were irradiated at 277K with 238Pu alpha-particles or USX in the presence of 10(-4) to 0.33 mol dm(-3) Tris and the yields of SSB and DSB determined by gel electrophoresis. Computer simulations, using Monte Carlo track-structure codes for 1.5keV electrons (CPA100) and 3.2MeV alpha-particle track segments (PITS), were used to obtain yields of DNA SSB and DSB at different *OH scavenger conditions. RESULTS: The experimental yield of SSB and DSB induced by AlK USX and SSB induced by alpha-particles and the dependences on the mean diffusion distance of the *OH are in reasonable agreement with the corresponding simulated yields and their corresponding dependences. However, for DSB induced by alpha-particles, a significant systematic difference exists between the simulated and experimental yields over the full *OH scavenging range, with the simulated yields being a factor of two to three greater than the experimental values. CONCLUSION: That the simulated yields of strand breaks are generally in reasonable agreement with those determined experimentally over a wide range of *OH scavenging capacities, increases confidence in the use of these simulations as a valuable source of quantitative, mechanistic information on DNA damage induced at very low radiation doses.     

Absorbed fraction of radon progeny in human bronchial airways with bifurcation geometry

Purpose : The absorbed fraction, defined as the portion of the initial particle energy which is absorbed in the tissue of interest, was calculated, under bifurcation geometry of the airway tubes, for alpha-particles emitted from radon progeny in the human respiratory tract. The results are given for all branching generations and compared with the data obtained for the commonly used infinite straight cylinders adopted by the International Commission on Radiological Protection (ICRP) Report 66. Materials and methods : A model was created to calculate the absorbed fraction of alpha-particle energy in the human lung using bifurcation geometry. Monte Carlo simulations of alpha-particle propagation in tissue and air were performed. The stopping powers of alpha-particles were adopted from the International Commission of Radiation Units and Measurements (ICRU) Report 49. Results : The absorbed fractions for the bifurcation geometry are given for the 15 generations in the tracheobronchial tree for alpha-particle energies of 6 and 7.69 MeV. The sources were assumed to be the fast and slow moving mucus. Conclusions : Comparisons with ICRP66 data reveal that the assumption of long, straight cylinders was appropriate in some cases, but not in all. Adoption of the absorbed fractions obtained from the bifurcation model instead of the ICRP66 data caused 'redistribution' of doses in the bronchial (BB) and bronchiolar (bb) regions.     

Uranium distribution and radon exhalation from Brazilian dimension stones

This paper provides evaluations of the radiometric behavior and exhalation patterns of radon gas in decorative and dimension stones explored in the Brazilian states of Minas Gerais and Espírito Santo, given the importance of determining radon gas concentrations in human-inhabited environments. A total of 10 silicate rock types were studied, featuring different petrographic/petrophysical characteristics given by seven magmatic rocks (three of which are granitic pegmatites) and three metamorphic rocks. The study, comprising radiometric data of U and monitoring of ²²²Rn gas exhalation, shows a strong correlation between petrographic parameters and the physical properties of rocks. U levels ranged between 2.9 and 37 ppm, revealing a good coherence between the presence and the absence of radioactive element-bearing accessory minerals for each rock type. The rate of radon exhalation from the stones is related to the petrographic/petrophysical features of each material. By comparing the ²²²Rn level generated by a rock to the amount effectively emanated by it, the rate of emanated gas proves to be insignificant; also, a rock that produces more Rn will not always emanate more. Simulations performed to estimate the radon levels inside residences or any given indoor environment showed that nine samples attained values below the 4 pCi/L EPA limit, whereas one was above that limit.