An investigation of radon exhalation rate and estimation of radiation doses in coal and fly ash samples.

Coal is a technologically important material used for power generation. Its cinder (fly ash) is used in the manufacturing of bricks, sheets, cement, land filling etc. Coal and its by-products often contain significant amounts of radionuclides, including uranium which is the ultimate source of the radioactive gas radon. Burning of coal and the subsequent atmospheric emission cause the redistribution of toxic radioactive trace elements in the environment. In the present study, radon exhalation rates in coal and fly ash samples from the thermal power plants at Kolaghat (W.B.) and Kasimpur (U.P.) have been measured using sealed Can technique having LR-115 type II detectors. The activity concentrations of 238U, 232Th, and 40K in the samples of Kolaghat power station are also measured. It is observed that the radon exhalation rate from fly ash samples from Kolaghat is higher than from coal samples and activity concentration of radionuclides in fly ash is enhanced after the combustion of coal. Fly ash samples from Kasimpur show no appreciable change in radon exhalation. Radiation doses from the fly ash samples have been estimated from radon exhalation rate and radionuclide concentrations.     

Radon exhalation and radiometric prospecting on rocks associated with Cu–U mineralizations in the Singhbhum shear zone, Bihar

The Singhbhum thrust belt is a 200 km long arcuate orogenic belt in Bihar, eastern India. The huge mineral resources, viz. copper, uranium, magnetite, apatite and molybdenite, etc., make it significant from an economic as well as a geological point of view. The belt hosts three types of mineralization: sulphides of copper and other metals, uranium oxides and apatite-magnetite. Several distinct geological episodes are responsible for the evolution of mineralization and the thrust zone itself. Extensive and reliable radiometric prospecting and assaying have been carried out by us for the past 5 years from Dhobani in the east to Turamdih in the west of the Singhbhum shear zone. The present work indicates uranium mineralization in the Pathargora–Rakha area presently being mined for copper and also within areas in the vicinity of Bhatin. Studies on radon emanation have also been undertaken in some parts of the shear zone which indicate reasonably high radon emanation of the soils and rocks studied. This suggests the need for regular monitoring and suitable controls on the mine environment (air quality) and its vicinity. Radon emanation studies coupled with gamma-ray spectrometry and the subsequent modelling of the radiometric and radon measurements will help in the application of radon as a geophysical tracer in exploration of radioactive ore bodies and in radon risk assessment as well as in delineating active and passive faults and even in petroleum exploration.     

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.     

INAA and DNAA for uranium determination in geological samples from Egypt

Uranium isotopes found in soil, rock, water, plants, air, etc., contribute to the natural radiation exposure of the population. U concentrations in some Egyptian environmental samples like Toshki soil, Aswan iron-ore, and phosphate samples from El-Sibayia in the Nile Valley and El-Quseir in the Red Sea coast were determined using instrumental neutron activation analysis (INAA) and delayed neutron activation analysis (DNAA) in the Mainz TRIGA research reactor. The results showed that the phosphate rocks are rich natural sources of uranium among the other minerals forming the earth crust.     

Procedures for the determination of 222Rn exhalation and effective 226Ra activity in soil samples.

Two methods for measuring 222Rn exhalation and effective 226Ra in soil samples were studied. In the first determination, the method employed was based on the adsorption of radon onto activated charcoal and subsequent measurement of the activity of its daughters with an HPGe (high-purity germanium) detector. In the second, vials containing an aqueous suspension of the sample, mixed with an insoluble high efficiency mineral oil scintillation cocktail, were measured using a low-level liquid scintillation counter. Studies of optimum sampling time, efficiency in both procedures, variation of 226Ra efficiency with quenching, as well as the effect of sample amount and granulometry upon the quenching parameter, were carried out. The two methods were applied to the determination of 222Rn exhalation and effective 226Ra in environmental samples.     

Procedures for the determination of Rn exhalation and effective Ra activity in soil samples

Two methods for measuring ²²²Rn exhalation and effective ²²⁶Ra in soil samples were studied. In the first determination, the method employed was based on the adsorption of radon onto activated charcoal and subsequent measurement of the activity of its daughters with an HPGe (high-purity germanium) detector. In the second, vials containing an aqueous suspension of the sample, mixed with an insoluble high efficiency mineral oil scintillation cocktail, were measured using a low-level liquid scintillation counter. Studies of optimum sampling time, efficiency in both procedures, variation of ²²⁶Ra efficiency with quenching, as well as the effect of sample amount and granulometry upon the quenching parameter, were carried out. The two methods were applied to the determination of ²²²Rn exhalation and effective ²²⁶Ra in environmental samples.     

Improved estimation of velocity and flow rate using regularized three-point phase-contrast velocimetry.

We improved the three-point phase-contrast method by regularization of MR velocity data after acquisition of a low velocity-to-noise ratio (VNR) velocity image and a high VNR aliased velocity image. The phase unwrapping algorithm is based on the assumed correlation of the velocity of adjacent flow voxels on the low VNR and the unaliased high VNR images. We used Fourier encoding with eight velocity-encoding gradient steps to obtain reference velocity images of the aorta from five subjects (274 images) and compared them with the phase-contrast and three-point phase-contrast images with and without regularization. The VNR of the regularized velocity image was improved by 9.1 dB and the VNR of the three-point phase-contrast velocity image was improved by 0.7 dB with respect to the low first moment velocity image. Corresponding improvements of 9 dB and 3.7 dB were obtained for the estimations of instantaneous flow rate. Magn Reson Med 44:122-128, 2000.     

Micro-column solid phase extraction to determine uranium and thorium in environmental samples.

Extraction chromatographic separation techniques based on U/TEVA and TEVA resins were utilized to separate uranium and thorium isotopes in complex matrices from environmental samples. This approach has the advantages of ease of quantitative analysis, small sample size, an absence of mixed waste solvents, complete separation of U/Th isotopes, acceptable chemical yields and good energy resolution in the alpha spectrum. The procedure for analyzing alpha-emitting isotopes of uranium and thorium in geothermal water from Peito, Taiwan, is illustrated in detail. It involves sample pre-concentration, filtration and separation by highly selective extraction chromatographic resins, followed by electroplating and alpha-spectroscopy. The analytical results show a chemical recovery exceeding 55% for U and 65% for Th, respectively, under optimized conditions. The efficient and cost-effective use of recyclable columns makes the analytical methods simple, accurate, rapid, reliable and robust.     

An improved radiochemical separation of uranium and thorium in environmental samples involving peroxide fusion.

A radiochemical procedure for the accurate determination of uranium and thorium using peroxide fusion followed by ion exchange and extraction chromatography is described. The method of extraction of the element from solid samples is the most important factor in the investigation. It is demonstrated, by measuring a number of reference materials, that fusion with Na(2)O(2) ensures a complete destruction of the mineral lattice and greatly improves the determination of the true activity of actinides.     

Study of the representativity of uranium and thorium assays in soil and sediment samples by alpha spectrometry.

The activity concentrations of soil and sediment samples are determined by alpha spectrometry with a sample size usually < 1 g. Hence, a systematic and careful procedure must be followed in the sampling and pre-treatment of the sample in order to ensure that the aliquot analysed represents the activity concentration of the entire sample. Statistical analyses of the activity concentrations of uranium and thorium isotopes in soil and sediment samples were performed to study the activity variation due to the lack of the representativity of the sample. These studies showed that, although some uncertainty in the determination of the sample activity concentration may be due to the lack of representativity (about 10%), the procedure followed for the pre-treatment of the sample can be considered adequate, providing an acceptable level of representativity.     

Investigation of the carbon dioxide distribution in cement bound wood samples using the radioisotope tracer technique

Cement bound wood bricks are widely used as building element for light construction buildings. Static characteristics of bricks can be considerably improved by treating the raw mixture of cement-wood-water with carbon dioxide during the bonding process. Distribution of the CO₂ among components and within the components is an important factor of the quality. Radioisotope tracer technique (RTT) was used for determining CO₂ uptake and distribution. Concentration of ¹⁴C-labelled carbon dioxide was measured by β-scintillation and liquid scintillation techniques and distribution of the CO₂ in the samples was visualized by autoradiography. RTT is more sensitive than the traditional analytical methods and is selective for the labelled CO₂ excluding the CO₂ present in the atmosphere.The physically bound CO₂ was determined after physical treatment (grinding and heating) of the samples. 79% of the CO₂ was bound physically. The chemically bound CO₂ was determined after a series of chemical treatments of the samples. The CO₂ bound in carbonate form was released from the samples by HCL and absorbed in KOH solution. 99.57% of the rest (CO₂ remained after physical treatment) was found in the carbonates. The CO₂ bound in the wood was determined by releasing the gas from the samples by H₂SO₄ and its rate was found to be 0.43%. No radioactivity was found in the silicates which remained after chemical treatments.As main parameters of the production technology, effect of the composition, treating time and CO₂ pressure on the CO₂ uptake was investigated by measuring some points of these relationships.     

An optimised and robust method for the determination of uranium and plutonium in aqueous samples

The paper describes a method for the separation of uranium and plutonium isotopes using anion exchange resin and UTEVA^™ resin in stacked sequential columns for routine analysis of river water and liquid effluent samples. The optimisation of the UTEVA^™ column for separation of U is described and compared with the conventional anion exchange technique for the separation of U from Fe. The stacked anion exchange and UTEVA^™ column configuration facilitates a more rapid and efficient separation of Pu and U and also reduces the quantity of reagents required for the separation.     

Radon in groundwater and dose estimation for inhabitants in Spas of the Sudety Mountain area,Poland

Studies of radon isotope ²²²Rn activity concentration in underground water in the Sudety region were performed with the use of the liquid scintillation technique. Waters chosen for investigations were collected in 24 health resorts and towns of the Sudety area from 115 springs, wells and intakes. The ²²²Rn activity concentration varied within the range from 4.2±0.4 to 1703±55 Bq/l. The annual effective doses due to the consumption of ²²²Rn with water were calculated for 50 sources of underground spring water or tap water used for consumption. The results were within the range from 0.003 to 1.1 mSv/yr, assuming 0.5 l of tap water per day from which radon is not removed or 0.5 l of mineral spring water consumed daily. The contribution to the effective dose from the inhalation of radon during the daily usage of domestic water substantially increases its effective dose.     

Concentration and characteristics of depleted uranium in water, air and biological samples collected in Serbia and Montenegro.

During the Balkan conflicts, in 1995 and 1999, depleted uranium (DU) rounds were employed and were left in the battlefield. Health concern is related to the risk arising from contamination of the environment with DU penetrators and dust. In order to evaluate the impact of DU on the environment and population in Serbia and Montenegro, radiological surveys of DU in water, air and biological samples were carried out over the period 27 October-5 November 2001. The uranium isotopic concentrations in biological samples collected in Serbia and Montenegro, mainly lichens and barks, were found to be in the range of 0.67-704 Bqkg(-1) for (238)U, 0.48-93.9 Bqkg(-1) for (234)U and 0.02-12.2 Bqkg(-1) for (235)U, showing uranium levels to be higher than in the samples collected at the control sites. Moreover, (236)U was detectable in some of the samples. The isotopic ratios of (234)U/(238)U showed DU to be detectable in many biological samples at all examined sites, especially in Montenegro, indicating widespread ground-surface DU contamination, albeit at very low level. The uranium isotopic concentrations in air obtained from the air filter samples collected in Serbia and Montenegro were found to be in the range of 1.99-42.1 microBqm(-3) for (238)U, 0.96-38.0 microBqm(-3) for (234)U, and 0.05-1.83 microBqm(-3) for (235)U, being in the typical range of natural uranium values. Thus said, most of the air samples are DU positive, this fact agreeing well with the widespread DU contamination detected in the biological samples. The uranium concentrations in water samples collected in Serbia and Montenegro were found to be in the range of 0.40-21.9 mBql(-1) for (238)U, 0.27-28.1 mBql(-1) for (234)U, and 0.01-0.88 mBql(-1) for (235)U, these values being much lower than those in mineral water found in central Italy and below the WHO guideline for drinking water. From a radiotoxicological point of view, at this moment there is no significant radiological risk related to these investigated sites in terms of possible DU contamination of water, air and/or plants.     

Determination of 222Rn in natural water samples from health resorts in the Sudety mountains by the liquid scintillation technique.

A method involving a Wallac 1414 WinSpectral alpha/beta liquid scintillation counter for determining 222Rn in aqueous samples is described. Samples were collected from 23 springs and 4 taps in health resorts of the Klodzka valley in the Sudety mountains in Poland. Half of the investigated spring water samples were radon enriched with an activity concentration higher than 74 Bq/l. In the tap waters the radon concentration level is very low or below the lower limit of detection. Owing to the statistical nature of radioactive decay the uncertainty of the measurement was determined as the standard deviation of 222Rn activity. The method introduced is fast and simple and does not require a chemical sample preparation procedure.     

Mapping of periodic waveforms using the ghost reconstructed alternating current estimation (GRACE) magnetic resonance imaging technique.

A new method of estimating alternating currents using ghost images created when the magnetic field from a fluctuating current modulates the phase of the magnetic resonance (MR) signal between successive phase-encode views is described. The method, known as ghost reconstructed alternating current estimation (GRACE), may be useful for directly mapping fields, and hence current impulses produced by neuronal firing events when synchronized periodic modulation can be induced. Images were acquired on a 1.5 T MR system with small oil capsule phantoms and a single wire with an applied alternating current, placed perpendicular to the main field direction. Computer simulations of these experiments yielded ghost images that agreed with experimental results. A simulated ghost image resulting from an evoked neuronal waveform is also discussed. Weak magnetic fields were detected from both sinusoidal and square wave modulations.     

Some tips on age estimation using DNA methylation in saliva samples as an index across the Japanese and Indonesian ethnicities

Age estimation of unidentified bodies is of marked importance in forensic medicine. In previous studies, the analysis of DNA methylation in body fluids led to the identification of several age-related CpG sites in genes such as EDARADD and FHL2. However, limited information is available on whether interethnic differences may affect the age prediction results. In the present study, we examined the effect of ethnicity on the age prediction method based on methylation scores, which were determined via methylation-sensitive high-resolution melting. We found that there was a significant difference in methylation scores between Japanese and Indonesian participants of early 20 s group, and that the nationality coefficient was significant for age estimation when applying the existing method for the analysis of the methylation status of EDARADD and FHL2. This suggests that when using certain biochemical indicators as a predictor of age, the effects of ethnicity on DNA methylation should be considered to improve the accuracy of the estimation.     

Determination of 210Pb and 210Po in soil or rock samples containing refractory matrices.

A new method has been developed for determination of (210)Pb and (210)Po in soil or rock samples containing refractory matrices. The samples were first fused with Na(2)CO(3) and Na(2)O(2) at 600 degrees C for pre-treatment and then (210)Pb and (210)Po were sequentially leached out at 200-250 degrees C with HNO(3)+HF, HClO(4) and HCl. About 10% of the leaching solution was used for (210)Po determination, carried out by spontaneous deposition of polonium on a silver disc from a weakly acidic solution that contained hydroxylamine hydrochloride, sodium citrate and (209)Po tracer, measurement being made by alpha-spectrometry. The remains of the leaching solution were used for determination of (210)Pb, conducted by precipitation as sulphate, purification with Na(2)S as PbS in 6M ammonium acetate, separation from alpha-emitters by an anion-exchange resin column, source preparation as PbSO(4), and measurement with a beta-counter. The procedure has been checked with two certified IAEA reference materials, showing good agreement with the recommended values. The lower limits of detection for 1g of analysed soil or rock samples were found to be 0.75 Bqkg(-1) for (210)Po and 2.2 Bqkg(-1) for (210)Pb. A variety of solid sample species analysed through use of the procedure gave average yields of 90.0+/-9.8% for (210)Po and 88.4+/-7.1% for (210)Pb.