India is the second largest producer of rice (Oryza sativa L.) in the world and rice is an essential component of the diet for a majority of the population in India. However, detailed studies aimed ...at the evaluation of radionuclide transfer factors (Fv) for the rice grown in India are almost non-existent. This paper presents the soil to rice transfer factors for natural (226Ra, 228Ra, 40K, and 210Pb) and artificial (137Cs) radionuclides for rice grown in natural field conditions on the West Coast of India. A rice field was developed very close to the Kaiga nuclear power plant and the water required for this field was drawn from the cooling water discharge canal of the power plant. For a comparative study of the radionuclide transfer factors, rice samples were also collected from the rice fields of nearby villages. The study showed that the 226Ra and 228Ra activity concentrations were below detection levels in different organs of the rice plant. The soil to un-hulled rice grain 40K transfer factor varied in the range of 6.5 × 10−1 to 2.9 with a mean of 0.15 × 101, and of 210Pb varied in the range of <1.2 × 10−2 to 8.1 × 10−1 with a mean of 1.4 × 10−1, and of 137Cs varied in the range of 6.6 × 10−2 to 3.4 × 10−1 with a mean of 2.1 × 10−1. The mean values of un-hulled grain to white rice processing retention factors (Fr) were 0.12 for 40K, 0.03 for 210Pb, and 0.14 for 137Cs. Using these processing retention factors, the soil to white rice transfer factors were estimated and these were found to have mean values of 1.8 × 10−1, 4.2 × 10−3, and 3.0 × 10−2 for 40K, 210Pb, and 137Cs, respectively. The study has shown that the transfer of 40K was higher for above the ground organs than for the root, but 210Pb and 137Cs were retained in the root and their transfer to above the ground organs of the rice plant is significantly lower.
► Soil to rice (Oryza sativa L.) transfer factors for radionuclides were determined under natural field conditions of West Coast of India. ► The mean values of soil to white rice transfer factors were 1.8 × 10−1, 4.2 × 10−3, 3.0 × 10−2 for 40K, 210Pb, and 137Cs, respectively. ► 40K transfer factor for straw was significantly higher than those of grain and root. ► 210Pb and 137Cs was retained in the roots of rice plants and its transfer to above the ground organs is lower. ► The radionuclide concentrations in plant were not linearly related to soil concentration.
Studies on natural radiation levels and radionuclides were carried out extensively in the environment of granite quarries of Kanakapura, Ramanagara Taluks and Bidadi Hobli in Bangalore rural District ...and Bangalore city. The indoor and outdoor gamma exposure rate in air was measured using an environmental dosemeter, and it is converted into absorbed dose using suitable conversion factor. The activity concentrations of natural radionuclides in rock samples and also in soil samples were measured using an HPGe gamma-ray spectrometer. The results reveal that the activity concentrations of 226Ra, 232Th and 40K in rocks are found to be vary from 32.2 to 163.6, 128.3 to 548.6 and 757.4 to 1418.4 Bq kg−1, respectively, with corresponding arithmetic mean values of 93.2, 306.2 and 1074.4 Bq kg−1. Activity concentrations of 226Ra, 232Th and 40K in soil samples were found to vary from 32.4 to 55.2, 39.9 to 214.3 and 485.4 to 1150.2 Bq kg−1, respectively, with corresponding arithmetic mean values of 40.7, 93.1 and 750.4 Bq kg−1. The average activity levels of all these radionuclides are above the global average. This is consistent with the geological and geo-chemical significance of the rocks of the area under investigation. The results of these systematic investigations are discussed in detail and compared with the literature values represented for other environments.
The International Commission on Radiological Protection dose limits for radiation protection have been based on linearly extrapolating the high-dose risk coefficients obtained from the Japanese A ...bomb survivor data to low doses. The validity of these extrapolations has been questioned from time to time. To overcome this, epidemiological studies have been undertaken across the world on populations chronically exposed to low-radiation levels. In the past decade, the results of these studies have yielded widely differing, and sometimes, contradictory, conclusions. While recent residential radon studies have shown statistically significant radon risks at low doses, high-level natural radiation (HLNR) studies in China and India have not shown any low-dose risks. Similar is the case of a congenital malformation study conducted among the HLNR area populations in Kerala, India. It is thus necessary to make efforts at overcoming the uncertainties in epidemiological studies. In the context of HLNR studies, assigning radon and thoron doses has largely been an area of considerable uncertainty. Conventionally, dosimetry is carried out using radon concentration measurements, and doses have been assigned using assumed equilibrium factors for the progeny species. Gas-based dose assignment is somewhat inadequate due to variations in equilibrium factors and possibly due to significant thoron. In this context, passive, deposition-based progeny dosimetry appears to be a promising alternative method to assess inhalation doses directly. It has been deployed in various parts of India, including HBRAs and countries in Europe. This presentation discusses the method, the results obtained and their relevance to dose assignment in Indian epidemiological studies.
The cumulative yields (i.e. the sum of isobaric independent yield up to the isobar of interest) for various fission products have been determined in the 8 MeV bremsstrahlung induced fission of ...sup.232Th and sup.238U by using off-line gamma ray spectrometric technique. From the cumulative yields of the fission products, their mass-chain yields (i.e. the sum of independent yields of all the isobars) were obtained by using charge distribution correction. The mass-chain yields in the sup.232Th(γ, f) and sup.238U(γ, f) reactions were compared with the data of similar excitation energy in the sup.232Th(n, f) and sup.238U(n, f) reactions to examine the effect of nuclear structure. From these data, it was found that the yields of fission products for the mass numbers 133-134, 138-140 and 143-144 as well as their corresponding complementary products are significantly higher than other fission products. Higher yields of the fission products around the mass numbers 133-134 and 143-144 were explained from the standard I and standard II asymmetric mode of fission, which indicates the role of shell closure proximity. However, the amplitude of yields for the mass numbers 133-134 and 143-144 are reverse in the sup.232Th(γ, f) and sup.232Th(n, f) reactions than in the sup.238U(γ, f) and sup.238U(n, f) reactions, which has been explained from the point of shell combinations of the complementary fragments. Keywords Nuclear reactions, sup.232Th(γ, f) and sup.238U(γ, f), E.sub.γ = 8 MeV bremsstrahlung, Measured fission product yields and mass-chain yield distribution, Off-line γ-pectroscopy using an HPGe detector, Comparison of fission yield between sup.232Th(γ, f) and sup.238U(γ, f) reactions
Tritium (3 H) is one of the important long-lived radioisotopes in the gaseous effluent from nuclear power plants. In this article, we present the results of 3 H monitoring in ambient air samples ...around the Kaiga Nuclear Power Plant, on the West Coast of India. Air samples were collected by moisture condensation method and the 3 H concentration was determined by liquid scintillation spectrometry. The 3 H concentration in the 2.3-15 km zone of the power plant varied in the range of < 0.04-6.64 Bq m-3 with a median of 0.67 Bq m-3 . The samples collected from the 2.3-5 km zone of the power plant exhibit marginally higher concentration when compared to the 5-10 km and 10-15 km zones, which is as expected. The values observed in the present study for Kaiga region are similar to those reported from other nuclear power plants, both within India and other parts of the world.
The present investigation aims to study the incorporation of uranium from the bedrock to groundwater through leaching. In view of this, rock powder samples were collected in the form of slurry from ...the bedrock of freshly drilled borewells of the study area. The rock powder and the supernatant were separated. The gamma activity concentrations of primordial radionuclides-238 U (226 Ra), 232 Th, and 40 K in the rock powder samples were measured using HP-Ge gamma-ray spectrometer. The supernatant was analyzed for the concentration of Unat using laser-induced fluorimeter. A strong positive correlation was observed between the concentration of uranium in the rock powder and the corresponding concentration in the water samples indicating the possible leaching of uranium from the bedrock to groundwater under favorable conditions.
Remediation of uranium contamination presents a significant environmental problem worldwide. Bioremediation has gained increasing importance as a feasible and eco-friendly strategy. Uranium tolerant ...phosphate solubilizing bacteria are considered as important candidates in the development of bioremediation technology. In this context, we have isolated bacteria from a proposed uranium mining site, Gogi in the Bhima river belt of Karnataka (South India) with special reference to phosphate solubilizers. Out of 270 bacteria isolated, 14 isolates solubilized 148.5–1226.6 mgL−1 phosphate from 5 g L−1 tri-calcium phosphate accompanied by drop in media pH from an initial 6.9 to pH values between 3.9 and 6.3. Phylogenetic analysis of 14 phosphate solubilizing bacteria by 16S rRNA gene sequencing grouped them into three phyla, namely Firmicutes, Proteobacteria and Actinobacteria. When tested for uranium sensitivity, 12 of the 14 phosphate solubilizing isolates showed significant (p < 0.01) tolerance to uranium (4.1%–26.1%) compared to the reference strain Escherichia coli ATCC 25922T. This demands further in-depth studies on microbial inhabitants from such complex environmental conditions that could provide better agents and insights for remediation technology.
•Uranium tolerant phosphate solubilizing bacteria (PSB) can be applied in U remediation.•The study presents PSB from a proposed uranium mining site in India.•These PSBs developed tolerance to U toxicity probably due to their adaptation.
Instrumental and preconcentration methods of neutron activation analysis (NAA) have been standardized for the determination of concentration of iodine in grass and cow milk samples, respectively. To ...study the transfer of iodine from grass to milk, known quantity of grass spiked with potassium iodide solution was fed to a cow. The spiked grass samples and milk samples, obtained from the cow after the ingestion of spiked grass, were collected. Iodine was separated from the milk samples chemically using Dowex 1X8 anion exchange resin. Spiked grass and ion exchange resin samples were neutron irradiated and radioactive assay was carried out using a 45 % relative efficiency HPGe detector coupled to an 8k channel analyzer. Iodine concentrations in spiked grass samples were found to be in the range of 1,487–2,002 mg kg
−1
. Concentration of iodine in milk after 12 h of feeding the cow with spiked grass was 871 ± 56 μg L
−1
which was reduced to 334 ± 32 μg L
−1
after 48 h.
A study on exhalation rates of 222Rn and 220Rn and their enrichment pattern in different grain size fractions was carried out. Four different size fractions of the sand samples (1000-500 μm, ...500-250 μm, 250-125 μm, and <125 μm) collected from the beach placers of south west coast of India were analysed for 226Ra and 232Th activity concentrations (Bq kg−1) by gamma spectrometry. Automated continuous measurement technique using scintillation cell based monitors were used to measure the 222Rn and 220Rn concentrations. These measured values were then fitted to appropriate model to extract the mass exhalation and emanation coefficients. The 222Rn mass exhalation rate varied from 0.7 ± 0.2 mBq kg−1 h−1 to 11.0 ± 0.9 mBq kg−1 h−1 while that of 220Rn varied from 88.5 ± 4.8 Bq kg−1 h−1 to 3066 ± 14 Bq kg−1 h−1. Higher mass exhalation rates, for both radioactive gases, were observed in finer grain size fractions. However, this was in contrast to the emanation coefficient values. Interestingly, higher radioactive monazite rich beach samples exhibited low emanation coefficient values compared to the low radioactive soil and sand samples reported in the literature. Statistical analysis showed a positive correlation, with correlation coefficient R = 0.84 and R = 0.79, respectively, between mass exhalation rates of 222Rn, 220Rn with their respective radioactive predecessors for different grain size fractions.
•This study throws light on the relative contribution of the monazite minerals to 222Rn and 220Rn release in the environment.•Monazite rich samples have a low emanation coefficient and are not the highest contributor of 222Rn and 220Rn to the environment.•Radon and thoron emanation coefficient was higher in 1000–500 μm grain size fractions, which contained the least 226Ra and 228Ra activity (Bq kg−1).•Unlike 226Ra and 228Ra activity concentrations, 222Rn and 220Rn emanation coefficient did not increase with the finer grain size; rather, the opposite trend was observed.•The statistically significant correlation coefficient substantiated the dependency of 220Rn mass exhalation rate (Bq kg−1 h−1) and 228Ra activity (Bq kg−1), also between 222Rn mass exhalation rate (mBq kg−1 h−1) and 226Ra activity (Bq kg−1).
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