Sorption of long-lived radionuclides onto main types of rocks of the Novaya Zemlya Archipelago

The ability of black carbonaceous siltstones and silt sandstones, lime sandstones, gray limestones, carbon–silicon carbonate schists with pyrite, and other rocks that most widely occur on the Novaya Zemlya Archipelago to sorb ¹³⁷Cs, ⁹⁰Sr, ^239+240Pu, and ²⁴¹Am was studied. The distribution coefficients K _d (cm³ g^–1) are as follows: for ^239+240Pu, 2.7 × 10³–7.7 × 10³; for 241Am, 2.5 × 10³–1.8 × 10⁴; and for ¹³⁷Cs, 1.1 × 10²–2.0 × 10³. Strontium-85(90) it not noticeably sorbed (within the measurement uncertainty) by any of the rocks studied. ^239+240Pu, ²⁴¹Am, and ¹³⁷Cs are strongly sorbed onto the rocks studied and are not noticeably desorbed from them with distilled water. The data obtained are required for predicting the migration of long-lived radionuclides generated by nuclear explosion with surface waters from test sites on the Novaya Zemlya Archipelago.     

Influence of temperature on the speciation of radionuclides sorbed onto rocks from the Nizhnekansky massif

The influence of temperature on speciation of actinides (Pu, Am) and some fission products (Cs, Sr), sorbed from simulated groundwater onto rocks from the Nizhnekansky massif (gneiss, dolerite) under anaerobic conditions at 20 and 90°С, was studied by sequential extraction. An increase in the contact temperature leads to an increase in the radionuclide uptake percentage and, in some cases, in the content of tightly fixed forms. The radionuclide species undergo redistribution with time.     

Natural radionuclides in zircon and related radiological impacts in mineral separation plants

The activity concentration of uranium and thorium present in zircon obtained from mineral sand industries are presented. External gamma radiation levels and inhalation of airborne dust are found to be the significant routes of radiation exposure to occupational workers. The annual average dose attributed to zircon processing is estimated to be 2.3 mSv in the plants under study. This paper presents the results of external gamma measurements, estimation of airborne radioactivity in zircon process locations and radon and thoron in the occupational environment of two mineral separation plants in India. Analyses of the solid wastes and liquid effluent generated and resultant environmental impacts are indicated.     

Natural radionuclides in borehole water in Port Harcourt, Rivers State, Nigeria

Water samples from boreholes collected from 29 locations in two local government areas in Port Harcourt, Rivers State, Nigeria have been analysed for their natural radioactivity content using a well-calibrated, shielded and highly efficient NaI(Tl) detector based gamma ray with a view to provide baseline data on the radioactivity level in the area, as well as an estimate of the resulting dose on the inhabitants. The radionuclides observed with reliable regularity belonged to the decay series chain headed by (238)U and (232)Th as well as the non-series (40)K. The mean specific activity concentrations of these, are 3.51 +/- 1.22, 2.04 +/- 0.29 and 23.03 +/- 4.37 Bq l(-1), respectively. The respective corresponding estimated mean annual effective dose are 0.36 +/- 0.12, 0.51 +/- 0.07 and 0.05 +/- 0.01, respectively mSv y(-1). These results are relatively high but are still below the recommended limit of 1 mSv y(-1) due to borehole water only. This study is the first in the area and can usefully be associated with similar surveys in other matrices in the area. Meanwhile, the radionuclides detected in the water samples do not seem to pose any radiological consequence on the sample population.     

Natural and anthropogenic radionuclides in the granitic region of Kapidag peninsula, Western Anatolia, Turkey

Naturally occurring radionuclides of terrestrial origin (also called primordial radionuclides) are present in various degrees in all media in the environment. This study represents the reports on the natural and anthropogenic radionuclides in the Kapidag granitic region. For this purpose, activities of radionuclides in soil, beach sands and rocks of the region have been investigated to assess the radiological hazard of the natural radioactivity. The radium equivalent activities, the absorbed dose rates and the external hazard indexes have been calculated, and also in situ gamma dose rates have been measured in the region. The mean activities of (238)U, (232)Th and (40)K with the ranges were determined as 31.1±15.7 (12.1-71.9), 42.5±15.9 (19.7-94.9), 590.3±192.2 (184.7-892.5), in the soil, as 16.5±9.5 (4.9-40.8), 67.1±106.9 (18.5-433.0), 569.2±212.6 (162.0-821.1) in the sand and as 25.4±12.8 (4.8-50.7), 37.8±21.5 (4.5-96.7), and 592.4±285.5 (62.4-1121.6) Bq kg(-1) in the rocks, respectively. It was also observed that the average activities of (137)Cs were ranged 0-27.8 Bq kg(-1) in the soil and 0.6-3.8 Bq kg(-1) in the beach sands. The mean Ra(eq) activities of the rocks, sands and soil were found to be 125.1±59.5, 156.3±157.2 and 137.3±48.8 Bq kg(-1), respectively, lower than the recommended maximum value of 370 Bq kg(-1) with some exceptions. The maximum contributors to the total absorbed gamma dose rates in air were determined as (238)U (45%) for the beach sands, (238)U (40%) for the soil and (40)K (41%) for rocks. The average outdoor gamma dose rates for the soil due to terrestrial and cosmic radiations were found to be 64.6±22.7 and 47.1±9.6 nGy h(-1), respectively, with the total of 111.7±29.5 nGy h(-1) outdoor gamma exposure rate and the annual average effective outdoor gamma dose was calculated as 137±36.2 μSv for the region. The results of the study were discussed with similar studies in close regions and the worldwide averages.     

Natural radionuclides contents and radon exhalation rates in building materials used in South Korea

The natural radionuclide (226Ra, 232Th and 40K) contents of building materials commonly used in South Korea have been determined by a gamma ray spectroscopy system using a high purity germanium detector. The radon exhalation rates and emanation coefficients of building materials have also been studied. The average concentrations of 226Ra, 232Th and 40K in building materials were in the range of 6.47-271 Bq.kg-1, N.D.-89.9 Bq.kg-1 and 16.8-1081 Bq.kg-1, respectively. The average radon exhalation rates and emanation coefficients were in the range of 0.0061-0.2404 Bq.kg-1.h-1 and 2.39-11.5%, respectively.     

Natural radionuclides content and associated dose rates in fine-grained sediments from Patras-Rion sub-basins, Greece

The activity concentrations of the natural radionuclides (238)U, (226)Ra, (232)Th and (40)K were measured in soil samples collected from the Patras-Rion sub-basins (Southern Greece) and were found to be 28, 27, 30 and 483 Bq kg(-1), respectively. These values compare well with the average Greek and worldwide values for crustal soil and sedimentary rocks. The mean (226)Ra/(238)U activity ratio was close to 1, implying secular radioactive equilibrium in the uranium series. All soil samples have Ra(eq) values lower than the limit of 370 Bq kg(-1), indicating their safe use in brick production. The average annual terrestrial absorbed dose rate in air was 51±14 nGy h(-1), and the average annual effective dose 0.06±0.02 mSv y(-1), which is consistent with the average worldwide exposure to external terrestrial radiation outdoors (0.07 mSv y(-1)). Non-significant differences between soils with different age and depositional environments were found, which could be attributed to a common source of sediments.     

Natural radionuclides and dose estimation in natural water resources from Elba protective area, Egypt

The concentrations of the natural radionuclides (226)Ra, (232)Th and (40)K in 15 different water samples from Elba protective area, south-eastern desert of Egypt, have been determined using NaI(Tl) detector. Gamma ray spectrometric analysis was performed and the concentrations obtained for each of the radionuclides expressed in Bq l(-1) ranging from 1.6 to 11.1 for (226)Ra, 0.21 to 0.97 for (232)Th and 9.1 to 23 for (40)K. A reasonable correlation was found between (226)Ra, (232)Th concentrations and pH, although no general trend was observed with conductivity and total dissolved solids. The mean effective doses of 0.56 mSv y(-1) for (226)Ra, 0.065 mSv y(-1) for (232)Th and 0.04 mSv y(-1) for (40)K were estimated for the ingestion of these waters by adults.     

Investigation of radionuclides in phosphogypsum

A determination was made of the content of uranium and²²⁶Ra in samples of phosphogypsum using gamma spectrometry. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 64–68, March, 1999.     

Infant doses from the transfer of radionuclides in mothers' milk

Assessments of potential internal exposures of the child following radionuclide intakes by the mother require consideration of transfers during lactation as well as during pregnancy. Current ICRP work on internal dosimetry includes the estimation of radiation doses to newborn infants from radionuclides ingested in mothers' milk. Infant doses will be calculated for maternal intakes by ingestion or inhalation of the radionuclides, radioisotopes of 31 elements, for which fetal dose coefficients have been published. In this paper, modelling approaches are examined, concentrating on models developed for iodine, caesium, polonium, alkaline earth elements and the actinides. Comparisons of model predictions show maximum overall transfer to milk following maternal ingestion during lactation of about 30% of ingested activity for 131I, 20% for 45Ca and 137Cs, 10% for 90Sr, 1% for 210Po and low values of less than 0.01% for 239Pu and 241Am. The corresponding infant doses from milk consumption are estimated in preliminary calculations to be about two to three times the adult dose for 45Ca and 131I, 70-80% of the adult dose for 90Sr, about 40% for 137Cs, 20% for 210Po, and <0.1% for 239Pu and 241Am. Infant doses from radionuclides in breast milk are compared with doses to the offspring resulting from in utero exposures during pregnancy.     

Migration of artificial radionuclides in the water stream of the Yenisei River

The distribution of artificial radionuclides between size fractions of the suspended matter in the bulk of the water stream of the Yenisei River near the Mining and Chemical Combine discharge sites was studied. The majority of radionuclides in the region of the discharge site were found to occur in the form of soluble salts or colloids with the particle size smaller than 0.2 μm. With an increase in the distance from the discharge site, the radionuclides undergo redistribution with the formation of coarser suspended particles due to coagulation. This fact was confirmed by mathematical simulation.     

Anisotropy of clays in diffusion transport of radionuclides

Comprehensive analysis of physicochemical and mineralogical properties of clays as surrounding rocks for radioactive waste repositories is performed with emphasis on the clay anisotropy. The results of a long-term experiment on diffusion transport of radionuclides in an experimental sample, a Cambrian clay monolith, are reported, and the anisotropy of the clay monolith with respect to diffusion properties along and perpendicular to the stratification plane is considered in detail.     

Association of radionuclides with colloids in soil solutions

Association of Pu and Am with variously sized particles in soil extracts is studied by ultrafiltration. In aqueous extracts, the Pu and Am concentrations depend on the soil type and aqueous solution composition. In the aqueous extracts, from 60 to 100% of the radionuclides and organic carbon are associated with fine colloidal particles (<0.05 μm). The presence of humic acid increases the recovery of radionuclides by a factor of 4–8 depending on the soil type. The Pu and Am distribution among the groups and fractions of humus acids is studied. In the group of humic acids of chernozem, from 65 to 75% of the radionuclides are associated with the fraction with MW > 100 kDa; about 25%, with the fraction with MW 50–10 kDa; and 2–4%, with the low-molecular-weight fraction with MW < 3 kDa. In the group of fulvic acids, 44–49% of the radionuclides is found in the fraction with MW > 100 kDa, and 42–51%, in the fraction with MW < 3 kDa.     

Natural radionuclide concentrations in granite rocks in Aswan and Central-Southern Eastern Desert, Egypt and their radiological implications

Different types of granites, used extensively in local construction, were collected from five localities in Egypt, namely: Abu Ziran (Central Eastern Desert), Gabal El Maesala (Aswan) and three areas from Wadi Allaqi, (Gabal Abu Marw, Gabal Haumor and Gabal um Shalman), in the South Eastern Desert. Granite samples were studied radiologically, petrographically and geochemically. The contents of natural radionuclides ((226)Ra, (232)Th and (40)K) were measured in investigated samples by using gamma spectrometry [NaI (Tl) 3'×3']. The activity concentrations of (226)Ra, (232)Th and (40)K in the selected granite samples ranged from 9±0.5 to 111±7, 8±1 to 75±4 and 100±6 to 790±40 Bq kg(-1), respectively. The external hazard index (H(ex)), absorbed dose and annual effective dose rate were evaluated to assess the radiation hazard for people living in dwellings made of the materials studied. The calculated radium equivalents were lower than the values recommended for construction materials (370 Bq kg(-1)). The excess lifetime cancer risks were also calculated. Petrographically, the granites studied are varied in the form of potash-feldspar, quartz, plagioclase, mica and hornblende. The accessory minerals are zircon, apatite and allanite. Geochemically, the chemical composition of the granite is studied especially for major oxides. They are characterized to have SiO(2), K(2)O, Na(2)O and Al(2)O(3) with depletion in CaO, MgO, TiO(2) and P(2)O(5).     

Local deposition distributions of inhaled radionuclides in the human tracheobronchial tree

There is experimental evidence that bronchogenic carcinomas originate mainly at the carinal ridges of the large central airways, where primary hot spots of deposition have been found. However, current lung dosimetry models do not take into consideration the inhomogeneity of deposition within the airways. In this study, computed local distributions of deposited inhaled radionuclides such as radon progenies in morphologically realistic human airway bifurcation models are analysed for different flow rates and particle sizes. Then, local deposition enhancement factors, defined as the ratio of local to average deposition densities, are computed by scanning along the surface of the bifurcation with pre-specified surface area elements. Computed enhancement factors indicate that cells located at carinal ridges or at the inner sides of the progeny branches may receive localised doses which are two orders of magnitude higher than the average values.     

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.     

Distribution of naturally occurring radionuclides in soils of the southern districts of Bangladesh

The activity concentrations of naturally occurring radioactive materials in soil samples of an elevated radiation background area of nine southern districts of Bangladesh were determined using gamma-ray spectrometry with an aim of evaluating the environmental radioactivity. The outdoor and indoor external effective dose rates and the radiation hazard indices from the soil activity were evaluated with an aim of minimising the harmful effects of ionising radiation to the population of the area concerned. The activity of (137)Cs was measured and observed in some of the locations.     

Factors affecting the transfer of radionuclides from the environment to plants

Much of our food directly or indirectly originates from plant material; thus, detailed studies on plant contamination processes are an essential part of international environmental research. This overview attempts to identify and describe the most important parameters and processes affecting the behaviour of radionuclide transfer to plants. Many parameters influence these processes. These parameters are related to: (1) plant, (2) soil, (3) radionuclide, (4) climate and (5) time. Often there is no boundary between the factors and they are linked to each other. Knowledge of important factors in radionuclide transfer to plants can help to assess and prevent radiological exposure of humans. This knowledge can also help to guide researches and modelling related to transfer of radionuclides to food chain.     

Speciation of Zr(IV) radionuclides in solutions

The speciation of Zr(IV) radionuclides at their concentration of ～10^?13 M in the solution was studied. The pH ranges where Zr(IV) exists as ions or as pseudocolloids were determined. The Zr⁴⁺ hydrolysis yields Zr(OH)³⁺ and Zr(OH) ₂ ²⁺ complexes. Their stability constants were calculated. At [Zr(IV)] > 1 × 10^?5 M, binuclear hydroxo complexes Zr₂(OH) _z+ ^x are formed.