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   Table of Contents - Current issue
July-September 2022
Volume 45 | Issue 3
Page Nos. 105-182

Online since Thursday, May 18, 2023

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What is required to make nuclear power acceptable to public? p. 105
MR Iyer
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Evolution of beryllium safety standards over the last 70 years and challenges ahead Highly accessed article p. 107
Munish Kumar, Alok Srivastava
Beryllium (Be), its alloys, and ceramics are widely used in high-tech applications such as electronics, space, atomic energy, and other day-to-day items of use. Initially, Be-based phosphors such as ZnBeSiO4 were being used in the lamp industry during the 1930s onward but were soon abandoned due to lung-related diseases and deaths of workers in the phosphor industry which was attributed to the highly toxic nature of Be. Typical effects associated with Be inhalation are chronic and acute Be diseases (CBD and ABD) and the main target organ being affected is the lung although effects on other human body organs are also well documented. Such diseases were observed not only in occupational workers handling Be but also in the members of the public residing in the neighborhood of Be manufacturing and processing facilities, especially in the USA. The CBD in occupational workers may depend on many factors such as individual's sensitivity to Be, amount of Be exposure, nature of Be compound, and types of Be operations and processes being performed. All this led to safety concerns about the toxicity of Be and recommendations regarding Be air concentration in the workplace and public environment were issued by the Department of Energy, USA in 1949 as occupational exposure limit (OEL)/threshold limit values (TLVs) which were 2.0 μg/m3 and 0.01 μg/m3 for occupational Be workers and public environment, respectively. It is worth to mention that these recommendations were adopted by various countries and organizations either as it is or with small changes. Later, different organizations recommended changes in the value of TLV for occupational workplaces, but such changes were never adopted as they were lacking sound epidemiological basis. The OEL/TLV of 2.0 μg/m3 continued for nearly 70 years until Occupational Safety and Health Administration (OSHA) in 2017 reduced the Be air concentration (BeAir-Conc) limit for occupational workers to 0.20 μg/m3 as the value of 2.00 μg/m3 was inadequate to protect occupational workers from CBD. This is a major change in the Be-related safety standards recommended recently and is/being adopted by many countries. The present article provides details about the evolution of Be safety standards over the last 70 years, the notion behind the recent revision of Be permissible exposure limit (PEL) value from 2.0 μg/m3 to 0.20 μg/m3 by OSHA and the associated safety challenges ahead. The information from literature about Be safety and related safety standards adopted in India is also given. The article also provides details about TLVs for BeAir-Conc being followed in various countries in the world and various challenges for the implementation of a revised PEL value of 0.20 μg/m3 as suggested by OSHA i.e., reduction in PEL value by a factor of 10 or recommendation of revised TLV of 0.05 μg/m3 by American Conference of Governmental Industrial Hygienists as compared to the previous value of 2.0 μg/m3. In view of different notations and limits for BeAir-Conc recommended by various agencies and limited information about Be safety-related details, all relevant information regarding Be safety along with the evolution of Be safety standards over the last 70 years is included in the present article. This is an important issue for the safety of individual's at occupational workplaces as well as for environmental safety and its compilation was highly needed for providing comprehensive information on Be safety from the inception of standards to till today.
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Equilibrium status of naturally occurring 226Ra with radon daughters and estimation of 238U activity from 235U using natural radioactivity ratio of 238U/235U in soil around Rawatbhata, Rajasthan p. 121
Ajay Kumar Gocher, Mohit Sisodia, SN Tiwari, IV Saradhi, A Vinod Kumar
Equilibrium status among 226Ra and radon daughters was studied in soil samples around Rawatbhata, Rajasthan. It was found that the increase in radioactivity of 214Bi (radon daughter) due to complete radon buildup in the sealed container is within 15% which establishes that 226Ra remains in equilibrium with radon daughter in soil of Rawatbhata. Radioactivity of 238U was estimated from the radioactivity of 235U using natural uranium isotopic radioactivity ratio (238U/235U) of 21.5. 238U radioactivity in soil was found in the range 25.8–49.5 Bq/kg with an average of 36.7 Bq/kg which is comparable to the global average of 35 Bq/kg.
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Estimation of aquatic dilution factor for liquid effluent discharges from Kaiga Generating Station using tritium as a tracer p. 127
TK Reji, RM Joshi, TL Ajith, Sanyam Jain, MS Vishnu, IV Saradhi, A Vinodkumar
Very low-level radioactive liquid effluents much below the approved discharge limits are discharged to Kadra reservoir after dilution with condenser cooling water at Kaiga Generating Station. In addition, further dilution occurs from the discharge point to the nearest public utilization point in Kadra reservoir (Hartuga). The dilution obtained in Kadra reservoir is estimated by simultaneous measurements of tritium at the discharge point and at Hartuga. The on-site measurement indicates a dilution factor of 12.2 ± 2.4 for tritium. A dilution factor of 13.3 ± 3.4 was obtained using aquatic dispersion model.
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Optimization of FLUKA detector model for HPGe array p. 131
CS Charubala, V Santhanakrishnan, G Ganesh, MS Kulkarni
Monte Carlo codes, such as FLUKA, are widely used to optimize calibration of spectrometric systems. HPGe detector array (HDA) for lung monitoring was modeled in FLUKA code using available information about their geometry and optimized for efficiency using 241Am point source at smaller distances (<10 cm) as in case of in-vivo monitoring scenarios. Thickness of dead layer (DL) on the top and lateral detector surfaces for low energy counting was determined by considering the experimental and simulated efficiency for various energies. Using trial and error method, optimized DL thickness was found out to be 2.5 μm on top surface and 1.8 mm on lateral surfaces for each HPGe detector in the array. For the optimized model, it was found that the simulated and experimental efficiency and the simulated and experimental spectra were in reasonable agreement. Optimization of the HDA was an important benchmarking step to reduce the simulation errors before they are implemented in complex numerical problems using computational phantoms.
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Theoretical evaluation of calibration factor for LR-115 cellulose nitrate solid state nuclear track detectors: A model for determining alpha radioactivity level in natural water p. 138
Biswajit Das, Argha Deb
Alpha-sensitive solid-state nuclear track detectors (SSNTDs) are used successively for decades for determining the alpha-radiation level in various environmental materials. A model for measurement of total alpha-radioactivity in natural water by using alpha-sensitive LR-115 type II cellulose nitrate (CN) film SSNTDs has been developed in the present work. The LR-115 CN films in bare mode are assumed to be immersed into a water sample for alpha-exposure. During the exposure time period, the alpha-particles that are emitted from the alpha-emitters present in the water sample will interact with the CN film and create their latent trails in the film. These latent trails will be manifested as pits of alpha-tracks after chemical etching of the exposed film. For alpha-radioactivity measurement, calibration factor (CF) for LR-115 type II SSNTDs has been evaluated theoretically by using the range of alpha-particles of residual energies situated between 1.6 MeV and 4.7 MeV in natural water and the actual geometry of experimental setup for alpha-exposure. The evaluated CF is found to be 204.93 Bq.l − 1.(tracks. cm − 2.h − 1)−1. The evaluated CF and experimental procedure can reliably be utilized in monitoring the alpha-radioactivity of natural water and in other radioactivity field measurements.
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A study on the level of terrestrial gamma and gross alpha activity in Gulf of Mannar, South coast of India, Tamil Nadu p. 153
Raju Krishnamoorthy, O Basith, M Jamal Mohamed Jaffer
This study presents the results of outdoor ambient gamma and gross alpha activity of Gulf of Mannar, and these measurements were carried out using Scintillation Counter (UR-705). Results showed that the terrestrial Gamma radiation levels of the Gulf of Mannar ranged from 4.10 μR/h to 76.33 μR/h. The Gross alpha radioactivity levels of the Gulf of Mannar ranged between 3.67 Bq/kg and 51.34 Bq/kg. The calculated ambient gamma and gross alpha activity were found to be lower than the world average. Gamma absorbed dose rates in air outdoors were calculated to be in the range between 35.67 nGy/h and 664.07 nGy/h with an arithmetic mean of 98.98 ± 20.54 nGy/h. This value is lower than the population-weighted world-averaged of 60 nGy/h. Inhabitants of Northern Gulf of Mannar are subjected to external gamma Annual dose exposure ranging between 0.30 and 5.65 mGy/y with an arithmetic mean of 0.84 ± 0.17 mGy/y.
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The behavior of mill tailings produced from a uranium extraction plant adapted an indigenously developed alkaline leaching-assisted process p. 158
Barendra Kumar Rana, Samim Molla, MR Dhumale, SK Jha, MS Kulkarni
The potential impact of tailings with respect to uranium and its associated toxic metals in the surrounding environment is assessed by identifying their concentrations and physicochemical behavior in the tailings. Tessier's sequential extraction method was used to study the speciation of U, Co, Zn, Mn, Fe, Pb, Cr, and Cd in different geochemical fractions of the alkaline mill tailings of the Tummalapalle process plant. The study indicated that uranium and other toxic metals present in the tailings have different chemical forms. Most of the toxic elements are not readily available in an exchangeable phase; rather, they are present in the tailings in stable complex form. However, a few elements, such as Co, Pb, and Cd, showed significantly higher concentrations in the oxidizing phase. The elements present in the oxidizing phases can be labile after prolonged exposure to atmospheric conditions. U (nat.) and Fe associated with the tailings are indicated to be mostly distributed in the residual phase. Radioactive disequilibrium of 238U and 232Th series radionuclides in the ore, waste rock, and tailings were studied. Disequilibrium was mostly noticed in the 238U series radionuclides in these matrices; however, the 232Th series radionuclides showed a radioactive equilibrium between their parents and daughters.
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Assessment of environmental radioactivity and groundwater quality around Tummalapalle uranium mining site, Andhra Pradesh, India p. 170
Barendra Kumar Rana, SK Jha, Samim Molla, MR Dhumale, MS Kulkarni
A comprehensive background radiological status in the surrounding environment of the Tummalapalle U mining and processing facilities was evaluated. Radioactivity in soil and rock was estimated by high-resolution gamma spectroscopy with a high-purity p-type germanium detector. The external gamma radiation level, outdoor 222Rn concentration, radioactivity in the groundwater, and water quality parameters around the Tummalapalle site were studied. The terrestrial radioactivity in soil was higher than the national and global averages in the study region. Radium equivalent activity (Raeq) in soil and rock was much lower than the safe limit of 370 Bq/kg and therefore safe to use as a construction material. Hydrogeochemical analysis indicated that the groundwater in the study region is neutral to medium basic, oxic, fresh to brackish, and predominantly Ca2+-Mg2+-HCO3 (62.5%) type. The hydrogeochemistry of groundwater was primarily governed by rock-aquifer interaction in this region. The data generated in this study can serve as the baseline for this region to understand the change in environmental conditions, if any, due to prolonged anthropogenic activities.
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