Assessment of radiological significance of naturally occurring radionuclides in soil and rock matrices around Kakrapar environment

The activity and gamma-absorbed dose rate due to the naturally occurring radionuclides in the terrestrial environment such as (238)U, (232)Th and (40)K were determined in soil and rock samples collected around Kakrapar Atomic Power Plant site, using gamma-ray spectrometry. The mean concentration levels measured in Kakrapar soil from naturally occurring radioisotopes such as (238)U, (232)Th and (40)K are lower than the corresponding global average values obtained in worldwide soil. The external hazard index (H(ex)) and absorbed gamma dose rate in air outdoors is observed to be 0.04-0.18 and 3.1-14.1 nGy h(-1), respectively.     

Distribution, enrichment and principal component analysis for possible sources of naturally occurring and anthropogenic radionuclides in the agricultural soil of Punjab state, India

Enrichment factor (EF) of elements including geo-accumulation indices for soil quality and principal component analysis (PCA) were used to identify the contributions of the origin of sources in the studied area. Results of (40)K, (137)Cs, (238)U and (232)Th including their decay series isotopes in the agricultural soil of Mansa and Bathinda districts in the state of Punjab were presented and discussed. The measured mean radioactivity concentrations for (238)U, (232)Th and (40)K in the agricultural soil of the studied area differed from nationwide average crustal abundances by 51, 17 and 43 %, respectively. The sequence of the EFs of radionuclides in soil from the greatest to the least was found to be (238)U > (40)K > (226)Ra > (137)Cs > (232)Th > (228)Ra. Even though the enrichment of naturally occurring radionuclides was found to be higher, they remained to be in I(geo) class of '0', indicating that the soil is uncontaminated with respect to these radionuclides. Among non-metals, N showed the highest EF and belonged to I(geo) class of '2', indicating that soil is moderately contaminated due to intrusion of fertiliser. The resulting data set of elemental contents in soil was also interpreted by PCA, which facilitates identification of the different groups of correlated elements. The levels of the (40)K, (238)U and (232)Th radionuclides showed a significant positive correlation with each other, suggesting a similar origin of their geochemical sources and identical behaviour during transport in the soil system.     

Assessment of the radiological hazards due to naturally occurring radionuclides in soil samples collected from the north western areas of Pakistan

(226)Ra, (232)Th and (40)K were measured in soil samples, these were collected from different localities of the North West Frontier Province and Federally Administered Tribal Areas, Pakistan. In order to measure the specific activities in these samples P-type coaxial high purity germanium based gamma-ray spectrometer was used. Average values of the measured activities of (226)Ra, (232)Th and (40)K were 26 +/- 11, 39 +/- 17 and 485 +/- 177 Bq kg(-1), respectively. Average radium equivalent activity was found to be 122 +/- 42 Bq kg(-1). External and internal hazard indices were also calculated and found to be 0.33 +/- 0.12 and 0.40 +/- 0.14, respectively. Average effective dose received due to gamma rays was 0.34 +/- 0.12 mSv y(-1). Measured natural radioactivity, hazard indices and effective doses received by the population were found within the recommended limits. The aim of this work was to make a baseline data of natural radioactive elements for the soil of the area and to assess it radiological significance if used as a building material for the construction of houses.     

Measurements of activity concentrations of naturally occurring radionuclides in soil samples from Punjab province of Pakistan and assessment of radiological hazards

The natural level of radioactivity in soil is one of the major causes of external gamma rays exposure. It was considered imperative to measure gamma-ray activity concentrations due to naturally occurring, potentially hazardous radionuclides from 232Th, 226Ra and 40K in soil samples from Punjab, the most populated province of Pakistan. The activity concentrations were measured in soil samples collected from all 34 district headquarters of Punjab province using a P-type coaxial high purity germanium (HPGe)-based gamma-ray spectrometer having a relative efficiency of 60%. The mean activity concentrations for 232Th, 226Ra and 40K were found to be 41 +/- 8, 35 +/- 7 and 615 +/- 143 Bq kg(-1), respectively in soil samples from all 34 district headquarters of Punjab. The mean values of radium equivalent index (Ra(eq)) and total annual external gamma radiation dose were found to be 141 +/- 27 Bq kg(-1)and 0.38 mSv, respectively. Since these estimated radiological impact assessment factors are lower than the recommended values there seems to be no potential radiological health hazard associated with the soils from the district headquarters in the Punjab province of Pakistan. Geological studies show that most of the soils in Punjab have developed on the extensive fluviatile deposits of five rivers and a stable ratio of natural activity concentrations is observed in soil samples of the areas under study.     

Regulation of naturally occurring radioactive materials in Australia

In order to promote uniformity between jurisdictions, the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) has developed the National Directory for Radiation Protection, which is a regulatory framework that all Australian governments have agreed to adopt. There is a large and diverse range of industries involved in mining or mineral processing, and the production of fossil fuels in Australia. Enhanced levels of naturally occurring radionuclides can be associated with mineral extraction and processing, other industries (e.g. metal recycling) and some products (e.g. plasterboard). ARPANSA, in conjunction with industry and State regulators, has undertaken a review and assessment of naturally occurring radioactive material (NORM) management in Australian industries. This review has resulted in guidance on the management of NORM that will be included in the National Directory for Radiation Protection. The first NORM safety guide provides the framework for NORM management and addresses specific NORM issues in oil and gas production, bauxite, aluminium and phosphate industries. Over time further guidance material for other NORM-related industries will be developed. This presentation will provide an overview of the regulatory approach to managing NORM industries in Australia.     

Fourier-transform infrared spectroscopic characterization of naturally occurring glassy fulgurites

We report here for the first time the spectroscopic characterization of natural fulgurites of Garuamukh. On April 22, 2005 at 04:00 local time, large amounts of black-brown colour of colloidal solution came out from below the earth’s surface at Garuamukh near Nagaon town (latitude 26°20′39″N, longitude 92°41′39″E, Assam, India) with fire and smoke. This colloidal solution got transformed into fulgurites, glassy material, within a few hours. We present here the characterization of the fulgurites by Fourier transform infrared (FTIR) absorption, X-ray diffraction and X-ray fluorescence methods. The amorphous nature of the substance has been confirmed by Fourier transform infrared spectra of the fulgurites, which exhibit prominent absorption band in the region 400–1200 cm⁻¹, the basic component of amorphous silica. The present study might have significant implications in understanding the thermodynamic properties of naturally occurring glasses, which are formed by shock metamorphism.     

Distribution of artificial radionuclides in lacustrine sediments in China

Establishing accurate historical records of the distribution, inventory and source of artificial radionuclides in the environment is important for environmental monitoring and radiological health protection due to their potential toxicity, and is also useful for identification and risk assessment of possible future environmental inputs of radionuclides from nuclear weapons tests and accidental release from the nuclear fuel reprocessing facilities or nuclear power reactors. A sector-field inductively coupled plasma mass spectrometer was used to study the recent sedimentation of Pu isotopes in 11 lakes in China. The distribution of (137)Cs was investigated using the conventional radiometric analytical methods. Based on the isotopic compositions of Pu and the activity ratio of (137)Cs/(239+240)Pu, the sources of artificial radionuclides were identified. The potential applications of Pu isotopes for sediment dating and for regional and global environmental change studies were discussed.     

Failure mode transition and energy dissipation in naturally occurring composites

The microstructural aspects of compressive inelastic deformation in balsa wood are investigated with emphasis on the failure mode transition and its effects on energy dissipation characteristics. The architectural features as well as the composite character of cell wall ultrastructure are discussed in a framework to understand the complex interrelationship between microstructure and macroscopic behavior in this extremely lightweight cellular biocomposite. Based on this discussion and experimental results, it is concluded that the biomimetic approach may prove to be a viable strategy in designing composite structures with high specific energy absorption capacity.     

Microstructural aspects and modeling of failure in naturally occurring porous composites

Results from an experimental investigation on the compression behavior of balsa wood are presented. Specimens with varying densities, ranging from 55 to 380 kg/m³, are loaded in the grain (fiber, cell) direction using a screw-driven material testing system at a strain rate of 10⁻³ s⁻¹. The results indicate that compressive strength of balsa wood increases with increasing density. Post-test scanning electron microscopy is used to identify the failure modes. The failure of low-density specimens is governed by elastic and/or plastic buckling, while kink band formation and end-cap collapse dominate in higher density balsa specimens. Based on the experimental results and observations, several analytical models are proposed to predict the compressive failure strength of balsa wood under uniaxial loading conditions.     

Study of natural radionuclide concentrations in an area of elevated radiation background in the northern districts of Bangladesh

The activity concentrations of naturally occurring radioactive materials in soil samples from an elevated radiation background area of three northern districts of Bangladesh were determined using gamma ray spectrometry. The outdoor and indoor external effective dose rates and the radiation hazard indices from these soil activities were evaluated. The dose rates were found to be about four times higher than the reported world average value. The concentration of natural radionuclides, derived radium equivalent activities and the representative level indices were also found to be higher. Recommendations on radiological and dosimetric measures have been suggested with an aim of minimising the harmful effects of ionising radiation to the population of the area concerned.     

Water sorption and desorption isotherms of some naturally occurring zeolites

Water sorption/desorption isotherms of some naturally occurring zeolites (more appropriately, zeolitic tuffs), such as chabazite, clinoptilolite, erionite, mordenite, and phillipsite, as measured by a volumetric method are reported. As expected, all the zeolites showed the Brunauer Type I isotherms with upward deviation at higher pressures, the latter as a result of multilayer sorption and liquid condensation in mesopores. The desorption branch of the isotherms exhibited small hystereses in all the samples. The micropore-filling capacities of the different zeolites were calculated from the Dubinin equation in order to delineate the effects of mesopores, impurities, crystallinity, and particle size. The Dubinin micropore-filling capacities were more or less found to be coincident to the Langmuir monolayer capacity.     

Assessment of radiological hazards of naturally occurring radioactive materials in cement industry

A study on the radiological hazard in Portland cement due to the presence of naturally occurring radioactive materials is being carried out. The Portland cement manufactured in the Islamabad/Rawalpindi region of Pakistan, intermediate products (clinker) and the various raw materials which compose the product have been analysed for (226)Ra, (232)Th and (40)K using a gamma spectrometry system with a N-type high-purity germanium detector of 80 % relative efficiency. From the measured gamma ray spectra, specific activities were determined. The mean values of the total specific activity of (226)Ra, (232)Th and (40)K are 34.2±11.9, 29.1±3.6 and 295.1±66.9 Bq kg(-1), respectively in Portland cement, 28.4±8.7, 11.3±1.7 and 63.1±17.3 Bq kg(-1), respectively in lime stone, 8.2±1.9, 16.2±3.9 and 187.7±53.2 Bq kg(-1), respectively in gypsum, 34.7±13.1, 41.2±6.7 and 187.6±17.2 Bq kg(-1), respectively in clay, 41.1±11.8, 39.3±6.9 and 195.1±29.2 Bq kg(-1), respectively in latrite and 51.1±18.2, 23.2±1.2 and 258.4±15.3 Bq kg(-1), respectively in clinker. The radium equivalent activities (Ra(eq)), external hazard index (H(ex)), internal hazard index (H(in)), absorbed dose rate in air (D) and annual effective dose rate (E(eff)) were also determined. The measured activity concentrations for these radio nuclides and radiological indices were compared with the reported national and international data. All these measured values are comparable with the worldwide data reported in UNSCEAR publications.     

Evaluation of occupational exposure to naturally occurring radioactive materials in the Iranian ceramics industry

Zircon contains small amounts of uranium, thorium and radium in its crystalline structure. The ceramic industry is one of the major consumers of zirconium compounds that are used as an ingredient at ～10-20 % by weight in glaze. In this study, seven different ceramic factories have been investigated regarding the presence of radioactive elements with focus on natural radioactivity. The overall objective of this investigation is to provide information regarding the radiation exposure to workers in the ceramic industry due to naturally occurring radioactive materials. This objective is met by collecting existing radiological data specific to glaze production and generating new data from sampling activities. The sampling effort involves the whole process of glaze production. External exposures are monitored using a portable gamma-ray spectrometer and environmental thermoluminescence dosimeters, by placing them for 6 months in some workplaces. Internal routes of exposure (mainly inhalation) are studied using air sampling, and gross alpha and beta counting. Measurement of radon gas and its progeny is performed by continuous radon gas monitors that use pulse ionisation chambers. Natural radioactivity due to the presence of 23?U, 232Th and ??K in zirconium compounds, glazes and other samples is measured by a gamma-ray spectrometry system with a high-purity germanium detector. The average concentrations of 23?U and 232Th observed in the zirconium compounds are >3300 and >550 Bq kg?1, respectively. The specific activities of other samples are much lower than in zirconium compounds. The annual effective dose from external radiation had a mean value of ～0.13 mSv y?1. Dust sampling revealed the greatest values in the process at the powdering site and hand weighing places. In these plants, the annual average effective dose from inhalation of long-lived airborne radionuclides was 0.226 mSv. 222Rn gas concentrations in the glaze production plant and storage warehouse were found to range from 10 to 213 Bq m?3. In this study, the estimated annual effective doses to exposed workers were <1 mSv y?1.     

Association of radionuclides with components of fulvic acids isolated from soils

The distribution of Pu and Am between specific and nonspecific components of various groups of the organic matter of soil was studied. For chernozem and soddy podzolic soil, 63 and 53% of Pu and only 1 and 8% of Am, respectively, are bound with fulvic acid purified to remove low-molecular-weight compounds by fractionation on BAU activated charcoal. Larger relative amount of Am, compared to Pu, in the form of low-molecular-weight nonspecific compounds is responsible for higher migration mobility of Am, compared to Pu, in the environment. The sorption of organic complexes of Pu and Am on carbon nanotubes was studied. The degree of Pu sorption only slightly depends on the nature of the organic substance, except solutions of humic acids from which the Pu sorption is appreciably higher. The degree of Am sorption regularly increases with a decrease in the molecular weight of the organic substances.     

Effect of basic chemical characteristics of soils on mobility of radionuclides in them

Interplay between the basic chemical characteristics of soils of the Belarussian Polessie and the tightness of fixation of Chernobyl-derived ¹³⁷Cs and ⁹⁰Sr in them is studied. The mobility of radionuclides in the soil proved to be controlled essentially by the soil type and organic matter content. In the investigated soils, nonexchange sorption of ¹³⁷Cs and exchange sorption of ⁹⁰Sr dominate.     

Occupational exposure due to naturally occurring radionuclide material in granite quarry industry

The potential occupational exposure in granite quarry industry due to the presence of naturally occurring radioactive material (NORM) has been investigated. The activity concentrations of (40)K, (226)Ra and (232)Th were determined using gamma-ray spectroscopy method. The annual effective dose of workers through different exposure pathways was determined by model calculations. The total annual effective dose varied from 21.48 to 33.69 μSv y(-1). Inhalation dose contributes the highest to the total effective dose. The results obtained were much lower than the intervention exemption levels (1.0 mSv y(-1)) given in the International Commission on Radiological Protection Publication 82.     

Heavy metal pollution of coal mine-affected agricultural soils in the northern part of Bangladesh

Total concentrations of heavy metals in the soils of mine drainage and surrounding agricultural fields in the northern part of Bangladesh were determined to evaluate the level of contamination. The average concentrations of Ti, Mn, Zn, Pb, As, Fe, Rb, Sr, Nb and Zr exceeded the world normal averages and, in some cases, Mn, Zn, As and Pb exceeded the toxic limit of the respective metals. Soil pollution assessment was carried out using enrichment factor (EF), geoaccumulation index (I_geo) and pollution load index (PLI). The soils show significant enrichment with Ti, Mn, Zn, Pb, As, Fe, Sr and Nb, indicating inputs from mining activities. The I_geo values have revealed that Mn (1.24 ± 0.38), Zn (1.49 ± 0.58) and Pb (1.63 ± 0.38) are significantly accumulated in the study area. The PLIs derived from contamination factors indicate that the distal part of the coal mine-affected area is the most polluted (PLI of 4.02). Multivariate statistical analyses, principal component and cluster analyses, suggest that Mn, Zn, Pb and Ti are derived from anthropogenic sources, particularly coal mining activities, and the extreme proximal and distal parts are heavily contaminated with maximum heavy metals.     

The contact properties of naturally occurring geologic materials: experimental observations

The discrete element method (DEM) is seeing widespread use in geotechnical applications and it is generally acknowledged that the validity of DEM simulations involving this class of materials depends critically on employing realistic contact laws. To support the development of such contact laws for common naturally occurring materials, we have conducted grain-to-grain contact experiments on several quartz sands, magnesite (limestone), crushed and ball-milled gneiss and ooids (precipitated calcium carbonate spheroids) and two reference materials (glass beads and the synthetic Delrin). Here we present the results of normal and shear contact experiments on these materials, with emphasis on the range of behavior encountered and aspects of behavior that deviate from current thinking on the topic. The development of contact laws based on the results presented herein, macroscopic frictional sliding and the implementation of the contact laws in DEM simulations are addressed in separate publications. The present experiments primarily examined the cyclic loading response, which allowed for a precise determination of normal and shear contact stiffness and loss compliances. Deformation generally consisted of elastic, anelastic and permanent components and the latter could be observed in shear prior to macroscopic sliding. Normal and shear stiffness ranged from 0.2–2.0 to 0.1–\(1.0\,\hbox {MN\,m}^{-1}\), respectively although the ratio of shear to normal stiffness for specific materials varied from 0.3 to \({\approx }1\). Frictional loss was observed to varying degrees in all of the contacts examined and internal friction in shear was found to be constant prior to the onset of permanent deformation. Internal friction ranged from barely perceptible to 0.1 for normal contacts and from 0.02 to 0.3 in shear. The modeling implications of the findings are examined as well.     

Distribution of natural and anthropogenic radionuclides in heavy rainfall areas in Jordan

Soil is the main reservoir of both natural and artificial radionuclides, which are transported to the human body through the food chain. Thus, assessment of the level of radioactivity in soil is of crucial importance. Artificial radionuclide concentrations in soil depend heavily on rainfall and weather conditions. In this study, the soil of the Ras Muneef area, which has the highest rainfall in Jordan, was investigated for its natural and anthropogenic radioactive content. The area was divided into four sectors and in each sector three locations were investigated depending on the land use: undisturbed, cultivated or residential. The depth profile of (137)Cs was investigated and found to depend on the land use. In the undisturbed soils, two types of depth profiles were identified: Gaussian and exponentially decreasing. The annual effective dose was found to range from 19.4 to 72.6 μSv, which falls within the worldwide ranges.