Radon Emanation in a Limestone Cave Using CR-39 and LR-115 Solid State Nuclear Track Detectors

Radon alpha-activities were evaluated in different places of a quaternary cave, by using solid state nuclear track detectors (SSNTD). The maximum activity was detected in the place more moved back of the studied cave. The ventilation phenomenon has been investigated. The radon alpha activity and uranium content according to the growth of stalagmite and stalactite samples from the cave were evaluated. A positive correlation has been shown between the uranium distribution (radon) and the stratigraphic order of the stalagmite (and stalactite) samples.     

Radon Mapping of Soils in St. Elizabeth, Jamaica

Soil gas measurements of radon were made in St. Elizabeth, Jamaica using nuclear track etch detectors. The results were compared to gamma-ray spectroscopy measurements made in the laboratory on soil samples collected at the radon measurement sites. An assessment of the degree of disequilibrium of uranium and thorium was also made by comparison with neutron activation analysis, delayed neutron counting and equivalent uranium and thorium measurements. The results to date for equivalent uranium and radon show a strong correlation and indicate the possibility of soil radon mapping in Jamaica using gamma-ray spectroscopy. Three anomalous sites have been identified.     

238U and 222Rn activity concentrations and total radioactivity levels in lake waters

The concentrations and distributions of natural radioactivity, uranium and radon in lake waters from around Van, Turkey were investigated with an aim of evaluating the environmental radioactivity. Fourteen lake waters were collected from different six lakes around Van (Turkey) to determine ²³⁸U, ²²²Rn and total alpha and total beta distributions in 2009. The total α and total β activities were counted by using α/β counter of the multi-detector low background system (PIC-MPC-9604) and the ²³⁸U concentrations were determined by inductively coupled plasma-mass spectrometry (Thermo Scientific Element 2) and radon concentrations were measured with the solid state nuclear track detector technique. The activity concentrations ranging from ND to 0.039 Bq L^?1 and from 0.026 to 3.728 Bq L^?1 for total alpha and beta, respectively, and uranium concentrations ranging from 0.083 to 3.078 μg L^?1, and radon concentrations varying between 47.80 and 354.86 Bq m^?3 were observed in the lake waters.     

The influence of the lithology and granulation on radon emanation in a sedimentary phosphatic deposit using solid state nuclear track detectors

Samples have been collected from different layers in a sedimentary phosphatic deposit and sieved. Different granulometric fractions have been selected. The uranium and thorium contents have been determined in each phosphate sample and its corresponding selected fractions. Radon (²²²Rn) α-activities per unit volume have been evaluated inside and outside each phosphate sample and its corresponding selected fractions by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD). The radon emanation coefficient in each phosphate layer has been determined and the global radon alpha activity outside a parallelepipedic block of the layers studied was evaluated. The influence of the lithology and granulation on the radon emanation has been studied.     

Use of radiometric emanation method in the characterization of anthropogenic glass analogue for vitrification of nuclear waste

Anthropogenic analogues can be used as one of the sources of information about long-term behaviour of engineered barriers, used for geological disposal of radioactive waste. The radiometric emanation method, based on the measurement of radon release from the solid samples, was used in the study of the alteration of anthropogenic glass analogues for radioactive vitrified waste. The samples were labeled at their surface by a solution containing ²²⁸Th and ²²⁴Ra,serving as source of ²²⁰Rn nuclides. The radon ²²⁰Rn nuclides were introduced in the uranium glass samples due to the recoil energy of the α-decay of ²²⁸Th and ²²⁴Ra nuclides. The man-made uranium glass samples from a locality in the Czech Republic were used. The measurement, based on the release of radon atoms from the samples, was applied to characterize the radon diffusion permeability and microstructure changes of weathered and non-weathered uranium glass samples during heat treatments. The radon diffusion characteristics and microstructure stability of the uranium glass analogue samples were evaluated by using a mathematical model.     

Possible correlation between uranium content in host rocks and radon and daughters concentration in air for two Italian ZnS-PbS mines

Research was carried out to evaluate the possible correlation between the uranium content in host rocks and the Rn and daughters concentration in air for two Italian ZnS-PbS mines. As a great variability had been ascertained for²²²Rn and daughters concentration in the different areas, it appeared of some interest to verify whether this fact was due to a different uranium concentration in the host dolomitic rocks or simply to a ventilation problem. Some rock samples were collected in several places where also radon and daughters were drawn; uranium was determined by fluorimetry and by alpha spectrometry after a chemical separation with a Microthene-TOPO column.²²²Rn was measured by the scintillation cell method, while the decay products were determined by the Markov and Tsivoglou methods. No correlation could be found between uranium content and radon concentration, but a good linearity was detected between the uranium content and the concentration of Rn decay products (alpha potential energy).     

Combined application of alpha-track and fission-track techniques for detection of plutonium particles in environmental samples prior to isotopic measurement using thermo-ionization mass spectrometry

The fission track technique is a sensitive detection method for particles which contain radio-nuclides like ²³⁵U or ²³⁹Pu. However, when the sample is a mixture of plutonium and uranium, discrimination between uranium particles and plutonium particles is difficult using this technique. In this study, we developed a method for detecting plutonium particles in a sample mixture of plutonium and uranium particles using alpha track and fission track techniques. The specific radioactivity (Bq/g) for alpha decay of plutonium is several orders of magnitude higher than that of uranium, indicating that the formation of the alpha track due to alpha decay of uranium can be disregarded under suitable conditions. While alpha tracks in addition to fission tracks were detected in a plutonium particle, only fission tracks were detected in a uranium particle, thereby making the alpha tracks an indicator for detecting particles containing plutonium. In addition, it was confirmed that there is a linear relationship between the numbers of alpha tracks produced by plutonium particles made of plutonium certified standard material and the ion intensities of the various plutonium isotopes measured by thermo-ionization mass spectrometry. Using this correlation, the accuracy in isotope ratios, signal intensity and measurement errors is presumable from the number of alpha tracks prior to the isotope ratio measurements by thermal ionization mass spectrometry. It is expected that this method will become an effective tool for plutonium particle analysis. The particles used in this study had sizes between 0.3 and 2.0 μm.     

Uranium Content Measurements in Building Materials Using Track Detection

In order to use the wood building materials in dwelling construction, uranium content measurements were performed by one of the alpha or fission track methods. The investigated samples were tree and rush samples, collected from different Romanian sites, situated in the vicinity of zones with human radioactive activities, such as: Sapantza, Izvorul Izei (North Romania), Omer and Periprava (Danube River Delta). We have examined the U atom distributions in these samples in order to detect any U contamination due to radioactivity. For each analysed sample, two U track micromappings were obtained in the two track detectors which were put in intimate contact with the sample during reactor neutron irradiations. The obtained track micromappings were studied by optical microscopy. The U distribution and content measurement results are presented and interpreted according to the present norms referring to maximum permissible values of U in building materials in Romania.     

Determination of the radon diffusion coefficient and radon exhalation rate in Moroccan quaternary samples using the SSNTD technique

Measurements have been made of radon (²²²Rn), release from diverse quaternary samples collected from different sediment deposits in the Errachidia and Beni-Mellal areas (Morocco). The radon diffusion coefficient as one of some important parameters of radon transport in the soil has been measured using solid state nuclear track detectors (SSNTD). Radon -activity, uranium content and radon exhalation rate have been determined in the studied samples. Uranium concentrations were found to vary from 0.14 to 9.52 ppm whereas the radon exhalation rate varied from 0.003 to 0.145 Bq^.m^-2.h^-1. A positive correlation has been found between radon exhalation rate and uranium content in the studied samples. The average radon diffusion coefficients were found to vary from (1.26±0.09)^.10^-6 m^2.s^-1 to (4.3±0.36)^.10^-6 m^2.s^-1. Furthermore, the correlation between ²²²Rn diffusion coefficient and porosity are also discussed.     

Peculiar radon spot in Hungary

For the public, indoor radon is the main source of exposure from ionizing radiation. Radon gas originates from the radioactive decay chain of uranium deposited in rocks or in building materials. In the reviews mostly a rather steady radon exhalation has been assumed. In a village of North-East Hungary, however, high radon concentrations have been measured, differing strongly in neighbouring houses and varying in time, due to the interplay of several geochemical phenomena.     

An automated system for track measurement for the employment of CR-39 as alpha spectrometer in radon and its daughters monitoring

In this work we studied an automated analysis of alpha particle tracks in CR-39, by employing a MITAKA photo-microdensitometer with a C1522 HAMAMATSU Image Analysis System. This system can be used to measure track diameters (with a nominal precision of 0.8 m), superficial track density, and track darkness. This information can be used to determine the alpha particle energies and also their incidence angles (azimuthal and zenithal). The performance of such an automated system, to analyze CR-39 samples which were exposed to alpha particles of known energies, was studied, comparing its response with measurements performed manually by experienced microscopists. The experimental results indicate that the MITAKA/HAMAMATSU system is very reliable for alpha track analysis in CR-39, making possible its use to perform time-consuming measurements in microscopy, as in the case of radon and its daughters surveys.     

Assessment of the natural radioactivity using two techniques for the measurement of radionuclide concentration in building materials used in Japan

The specific activities of ²³⁸U, ²³²Th, and ⁴⁰K in selected building materials used in Japan were measured using a high-purity germanium detector. The uranium and thorium concentrations were determined from same samples using inductively coupled plasma mass spectrometry. There was a good agreement between the measurement of uranium and thorium with both methods (R ² = 0.94, and 0.97, respectively). Based on the specific activities, we have estimated some hazard indexes such as radium equivalent activities (Ra _eq), external hazard index (H _ex), internal hazard index (H _in), annual gonadal equivalent dose (AGED), internal alpha dose, mass exhalation rate and emanation coefficient of radon.     

The influence of the lithology and depth on water recharge of wells in two Moroccan Atlantic coastal regions by using solid state nuclear track detectors and radon as a natural tracer

Uranium and thorium contents as well as radon and thoron -activity concentrations were evaluated inside different underground 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 uranium nitrate standard solutions. A relationship between water radon concentration and recharge of wells dug in two Moroccan Atlantic coastal regions, for a given lithology, was found. The influence of the lithology and depth on radon concentration and salinity of well waters studied was investigated.     

Radioxenon net count calculations revisited

To obtain the relationship between radon solubility and temperature, salinity, and pH of radon-bearing water in in situ leaching uranium mines, an experimental device for measuring the radon solubility in water was designed and manufactured. According to the range of temperature range, salinity, and pH of radon-containing radioactive water from in situ leaching mines in China, aqueous radon solubilities at different temperatures and salinities were determined using an orthogonal design and, concurrently, radon solubilities at different pH also determined. An empirical equation for estimating the radon solubility in radioactive water containing radon in uranium mining and metallurgy is proposed.

     

Estimation of indoor radon and the annual effective dose from building materials by ionization chamber measurement

Indoor radon and its annual effective dose from the building materials commonly used in Thailand were reported. Radon emission from samples collected in the closed chamber was measured by an ionization chamber. Indoor radon and the annual effective dose were calculated from radon concentration in the closed chamber. Granite yields the highest annual effective dose. Three samples of granite shown the annual effective dose higher than the annual exposure limit for the general public of 1 mSv year^?1 recommended by the International Commission on Radiological Protection. Applying appropriate surface coating, the radon emission from some building materials has decreased substantially.     

Measurements of222Rn migration in soil

The concentration of radon (²²²Rn) was measured in the soil near the ground surface, using CR/39 solid state nuclear track detectors. The measurements were carried out in PVC tubes at 0.25 m intervals up to 1.25 m. The detectors were etched in 7N NaOH solutions at 80°C. The -tracks from radon's decay were counted using a microscope. A microscope-camera-computer system developed for automatic counting was also used. The results provide evidence for the non-diffusive transport of radon in soils. A transport length of (46.9±3.2) cm was estimated for radon transport near ground surface. Also the variation of soil's radon concentration was correlate to humidity and atmospheric pressure.     

Nuclear analytical techniques for quantification of uranium for its recovery from seawater

Nuclear analytical techniques namely fission track technique using solid state nuclear track detector (SSNTD) and instrumental neutron activation analysis (INAA) have been standardized and applied for quantification of low uranium concentrations in liquid samples such as feed, elute and brine and solid sorbent samples respectively. The quantification of uranium is required for its recovery study from seawater, which is one of the potential sources of uranium. The uranium concentration of a liquid sample obtained by SSNTD method was compared with the other well established conventional techniques like ICP-MS, ICP-AES, adsorptive stripping voltametry and alpha spectrometry. INAA was applied for uranium concentration determination in the radiation grafted polyamidoxime sorbent samples.     

Elemental analysis of fertilizers using X-ray fluorescence and their impact on alpha radioactivity of plants

The fertilizers used for plantation contain different elements including some natural radionuclides with their daughter decay products. The radiological impact of the use of fertilizers may be due to internal irradiation of the lung by the alpha particles, short lived radon-thoron progeny and the external irradiation of the body by gamma ray emitted from the radionuclides. The aim of this study was to estimate the enhanced alpha radioactivity in different parts of plants due to fertilizers and to measure the concentration of different elements present in the fertilizers. A control study was carried out on round gourd plants using different fertilizers. Fertilizers were added to the soil just before the plantation of seeds in the pots. For the measurement of alpha track densities in different parts of plants we used α-sensitive LR-115 type II plastic track detectors. The alpha-track density (T cm^?2 days^?1) was measured in leaves of plants at different interval of time. The variation in alpha track densities was also observed in root, stem leaf and grain parts of the plants. In case of the plants grown using some phosphate fertilizers the alpha radioactivity was found to be more compared with others. A positive correlation between alpha track densities and mass exhalation rates of radon from different fertilizers has been observed. The concentration of major elements (Al, Si, P, S, Cl, K) along with other elements present in fertilizer samples was measured by X-ray fluorescence analysis.     

A new method for studying the influence of pollution and soil nature on the radon emanation from water samples by using solid state nuclear track detectors

Radon emanation from surface water and groundwater samples has been studied by using CR-39 and LR-115 solid state nuclear track detectors (SSNTD). A calibration method for determining the thoron and radon concentrations of the water samples studied has been developed. The effect of pollution due to coal fly ashes, cement and granite dusts on the radon emanation from water samples has been investigated. The influence of the radon source on the radon emanation rates from water samples has been studied.     

龙门山山前断裂带中氡活度浓度的检测

对龙门山山前断裂带两侧表土中氡活度浓度进行了检测.结果表明,不同地层中,由于铀、钍等放射性元素含量的不同,其土壤中氡浓度也存在着明显的差异;在第四纪地层中,氡活度浓度的变化视表土的干湿程度、空隙度等而论,其变化范围存在很大差异.