Atomic Energy Regulatory Board

Phenotypic mutants of Sporosarcina pasteurii (previously known as Bacillus pasteurii) (MTCC 1761) were developed by UV irradiation to test their ability to enhance urease activity and calcite production. Among the mutants, Bp M-3 was found to be more efficient compared to other mutants and wild-type strain. It produced the highest urease activity and calcite production compared to other isolates. The production of extracellular polymeric substances and biofilm was also higher in this mutant than other isolates. Microbial sand plugging results showed the highest calcite precipitation by Bp M-3 mutant. Scanning electron micrography, energy-dispersive X-ray and X-ray diffraction analyses evidenced the direct involvement of bacteria in CaCO3 precipitation. This study suggests that calcite production by the mutant through biomineralization processes is highly effective and may provide a useful strategy as a sealing agent for filling the gaps or cracks and fissures in any construction structures.

Microbiologically induced calcite precipitation by the bacterium Sporosarcina pasteurii (NCIM 2477) using the industrial effluent of the dairy industry, lactose mother liquor (LML) as growth medium was demonstrated for the first time in this study. The urease activity and the calcite precipitation by the bacterium was tested in LML and compared with the standard media like nutrient media and yeast extract media. Calcite constituted 24.0% of the total weight of the sand samples plugged by S. pasteurii and urease production was found to be 353 U/ml in LML medium. The compressive strength of cement mortar was increased by S. pasteurii in all the media used compared to control. No significant difference in the growth, urease production and compressive strength of mortar among the media suggesting LML as an alternative source for standard media. This study demonstrates that microbial calcite acts as a sealing agent for filling the gaps or cracks and fissures in constructed facilities and natural formations alike.

Abstract This paper investigates the propagation of Rayleigh surface waves in a rotating semi-infinite solid medium, permeated by an initial magnetic field in the context of linear nonlocal elasticity. Frequency equations are derived and the combined effect of magnetic field and rotation on Rayleigh wave propagation, based on the linear theory of nonlocal elasticity has been studied. Effects of magnetic field, as well as rotation on Rayleigh wave propagation in a nonlocal medium, have also been analyzed in details as special cases. Numerical calculations, graphs and discussions presented in this paper lead us to some important conclusions. Fourier double integral transform technique has been applied to solve the problem.

Linearity in dose response up to very high radiation doses and sufficient sensitivity to even low radiation doses are extremely important for the measurement of radiation dose in the field of radiation technology, ranging from medical to industrial applications. Olivine type LiMgPO4 has been shown immense interest as a phosphor material in the fields of thermoluminescence and optically stimulated luminescence dosimetry. In the present study, we have explored the role of different vacancy defects in the optical properties of LiMgPO4 aiming at enhancing its sensitivity for the measurement of radiation dose. For this purpose, we have systematically investigated the electronic structure of LiMgPO4 in the absence and presence of various vacancy defects using density functional theory as a tool. The present study considers all possible vacancy defects including neutral, charged and mixed lattice vacancy defects in LiMgPO4. To find the most energetically favourable vacancy defect, we have compared the defect formation energy of all the vacancy defects. We have also calculated vacancy formation energy in different chemical environments to investigate how the formation of different types of vacancy defect can be controlled by tuning the chemical environment. Finally, the origin of the different optical properties of LiMgPO4 has been explained by using a possible mechanism based on our detailed electronic structure calculations. Thus, the present study is believed to provide valuable insight for the development of materials with improved features for the measurement of radiation dose.

Thermoluminescence glow peaks are calculated numerically for a one-trap-one-recombination-centre model using a generalized approach. Except in extreme cases the peaks are seen to change in position and shape with a change in dose. These glow peaks are fitted to the general-order kinetics model and the values of the kinetic parameters, namely the activation energy, pre-exponential factor and order of kinetics are determined by finding the best fit. in this way an attempt is made to correlate the empirical parameters with the physically meaningful ones in the framework of the adopted model. the fitted value of the activation energy matches reasonably its input value used in the generalized approach model calculations. the fitted values of the order of kinetics and the pre-exponential factor parameters change with the initial occupancy of the traps (dose) in all cases in which the order of kinetics (KO) is found to be in the range in which 1 < KO < 2. the KO decreases with increasing trap occupancy whereas the pre-exponential factor increases. the latter parameter undergoes a change also in its units. It is observed that, when the found value of the KO is such that 1 < KO < 2, the best fitted general-order kinetics peak deviates significantly from the computed peak. A better fit is found with two peaks, one of which is approximately of first order and the other approximately of second order. the KO parameter at saturation dose has been correlated with the ratio of the re-trapping and recombination cross sections. These theoretical results are discussed in the perspective of experimental observations in general. Plausible reasons for disagreements between theory and experiment are also discussed.

Abstract Neodymium‐doped glass finds application in lasers with high energy and low pulse width. In the present study, a series of Nd 3+ ions (0–2 mol%)‐doped strontium borophosphate (SBP) glass samples was prepared through the conventional melt quench method. A broad peak in the X‐ray diffraction spectrum confirmed the formation of a single‐phase amorphous borophosphate glass. Fourier transform infrared spectra of the doped and undoped glass samples indicated the presence of borate and phosphate groups that form the anionic network. The thermal properties of the glass samples were determined from thermogravimetry/differential thermal analysis. Photoluminescence and ultraviolet–visible light techniques were used to investigate the optical properties of the as‐prepared SBP:Nd glass. The Judd–Ofelt (JO) intensity parameters Ω λ (2, 4, 6), stimulated emission cross‐section, branching ratios, and transition probabilities of the Nd 3+ ‐doped glass were obtained through the JO analysis. Characteristic Nd 3+ emission peaks were observed at 1330, 1060, and 876 nm, corresponding to the 4 F 3/2 → 4 I S/2 (S = 13, 11, and 9) transitions, respectively. The suitability of SBP:Nd (0.5 mol%) glass for use in solid‐state lasers was demonstrated by its intense luminescence, high transition probability, high emission cross‐section, optical gain, and luminescence branching ratio.

The present work deals with the generation of H2 through water splitting using titania (TiO2) nanotubes (NTs) prepared via rapid breakdown anodization. The anatase TiO2 NTs sensitized with Pt, Pd and Ni nanoparticles (NPs) to investigate the efficiency of water splitting of these nanocomposites. The Pt, Pd and Ni NPs were loaded over TiO2 NTs through chemical reduction of the respective precursors. The morphology of the TiO2 NTs was observed to be produced as bundles. The metal NPs sensitized TiO2 NTs as spherical deposits. The H2 generation is larger with the addition of metal NPs and moreover lower quantity deposits produced better results. Pt NPs addition was better among the group in terms of H2 generation over the other metals of the same group. The Pt/TiO2 NTs with 5% metal sensitization generated H2 with a specific release rate of 241.8 μmol g−1 min−1.

This paper focuses on the mild steel (MS) corrosion detection and intercomparison of results obtained by gamma scattering, gammatography, and radiography techniques. The gamma scattering non-destructive evaluation (NDE) method utilizes scattered gamma radiation for the detection of corrosion, and the scattering experimental setup is an indigenously designed automated personal computer (PC) controlled scanning system consisting of computerized numerical control (CNC) controlled six-axis source detector system and four-axis job positioning system. The system has been successfully used to quantify the magnitude of corrosion and the thickness profile of a MS plate with nonuniform corrosion, and the results are correlated with those obtained from the conventional gammatography and radiography imaging measurements. A simple and straightforward reconstruction algorithm to reconstruct the densities of the objects under investigation and an unambiguous interpretation of the signal as a function of material density at any point of the thick object being inspected is described. In this simple and straightforward method the density of the target need not be known and only the knowledge of the target material's mass attenuation coefficients (composition) for the incident and scattered energies is enough to reconstruct the density of the each voxel of the specimen being studied. The Monte Carlo (MC) numerical simulation of the phenomena is done using the Monte Carlo N-Particle Transport Code (MCNP) and the quantitative estimates of the values of signal-to-noise ratio for different percentages of MS corrosion derived from these simulations are presented and the spectra are compared with the experimental data. The gammatography experiments are carried out using the same PC controlled scanning system in a narrow beam, good geometry setup, and the thickness loss is estimated from the measured transmitted intensity. Radiography of the MS plates is carried out using 160 kV x-ray machine. The digitized radiographs with a resolution of 50 μm are processed for the detection of corrosion damage in five different locations. The thickness losses due to the corrosion of the MS plate obtained by gamma scattering method are compared with those values obtained by gammatography and radiography techniques. The percentage thickness loss estimated at different positions of the corroded MS plate varies from 17.78 to 27.0, from 18.9 to 24.28, and from 18.9 to 24.28 by gamma scattering, gammatography, and radiography techniques, respectively. Overall, these results are consistent and in line with each other.

AbstractHydrogen generation during the progression of an accident in a nuclear reactor and its release into the containment comprise an important safety concern in the management of severe accidents in nuclear power plants. The distribution of hydrogen within the containment has important bearing on possibility, mode, and consequence of combustion in the containment. Hence, several small- and large-scale facilities have been built to study the distribution of released hydrogen. Further, several numerical studies and intercomparison exercises on hydrogen distribution have been carried out. The present review summarizes the experimental and numerical studies on hydrogen distribution and suggests opportunities for further studies. ACKNOWLEDGMENTThe authors express their sincere gratitude to the Atomic Energy Regulatory Board for its support of the hydrogen safety program at the AERB-Safety Research Institute, Kalpakkam, and the Indian Institute of Technology, Madras, Chennai-36.Additional informationNotes on contributorsNilesh AgrawalNilesh Agrawal is a scientist at the Safety Research Institute, Atomic Energy Regulatory Board, Government of India. He received his B.Tech. and M.Tech. from the Indian Institute of Technology, Bombay, in 2000 and 2006 and his Ph.D. from the Indian Institute of Technology Madras, India, in 2013. He has 11 years of industry and research experience and has published 15 research papers in reputed international journal and conferences. His research interests include computational fluid dynamics, heat and mass transfer, nuclear reactor thermal hydraulics, hydrogen distribution and mitigation, reactor safety, and severe accident management.Aneesh PrabhakarAneesh Prabhakar is a Ph.D. scholar at Heat Transfer and Thermal Power Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, India. He received his M.Tech. in thermal sciences from National Institute of Technology Calicut, Kerala, India, in 2010 and B.Tech. in mechanical engineering from Sree Chitra Thirunal College of Engineering, Pappanamcode, Thiruvananthapuram, University of Kerala, India, in 2008. Currently, he is working on the experimental and numerical analysis of the hydrogen–steam–air mixture distribution in AIHMS.Sarit K. DasSarit K. Das is a professor in the Department of Mechanical Engineering and the Dean, Academic Research at Indian Institute of Technology Madras. He has published four books and more than 200 research papers. He is the editor-in-chief of Inter-national Journal of Micro-Nano Scale Transport and also an associate editor of Journal of Heat Transfer Engineering. His research interests include heat transfer in nanofluids, microfluidics, biological heat transfer, nanoparticle-mediated drug delivery in cancer cells, heat exchangers, boiling in mini-/microchannels, fuel cells, jet instabilities, heat transfer in porous media, and computational fluid dynamics. He is a recipient of the DAAD and Alexander von Humboldt Fellowship of Germany. He is a fellow of the Indian National Academy of Engineering and National Academy of Sciences, India. He is a recipient of the Thomson Reuters Research Excellence—India Citation Awards 2012 based on citation impact analysis conducted by Thomson Reuters. He was awarded the Peabody Visiting Professorship at the Mechanical Engineering Department of Massachusetts Institute of Technology (Cambridge, MA), 2011.

In this study, emissions between 350 nm and 2.8 μm are produced from molten-salt-synthesized LaF3:Yb3+,Er3+ (LFYE) nanocrystals (NCs) under 980 nm excitation. In fact, such wide spectral emissions from a single phosphor would be highly favorable in lighting applications ranging from light-emitting diodes, optical fibers, and telecommunications. Upconversion luminescence (UCL) spectra show intense red emission compared to the green band below 6 mW, wherein a strong green emission is achieved compared to a red emission when the laser power is increased beyond 85 mW. To further enhance their UCL and downconversion luminescence (DCL), the LFYE NCs are annealed at 400 °C for 30, 60, 90, and 120 min. Their UCL and DCL intensities are improved with up to 90 min of annealing but drastically reduced after annealing for 120 min. The latter is caused by both phase transition and shape changes, that is, from the cubic LFYE NCs to tetragonal LaOF:Yb3+,Er3+ (LOFYE) NCs with a square pyramidal shape. Density functional theory calculations show that the LOFYE NCs are more thermodynamically favorable to form due to their lower defect formation energy than the LFYE NCs. Moreover, LaF3 is dynamically more unstable in comparison to LaOF, as indicated by a greater number of imaginary modes for LaF3 in the phonon dispersion plot. Interestingly, the highest phonon energy for LaF3 is found to be 439 cm–1 while that of LaOF is 527 cm–1, which is expected to play a role in the different emission behaviors between LaF3 and LaOF. Our work shows exemplary potential of the LFYE NCs with near-ultraviolet to mid-infrared emissions as UCL and DCL for laser power-induced color tunability for a wide range of applications.

Significant research has been carried out in ABO3 perovskites during last decades in tailoring their luminescence properties for advanced optoelectronics. However, research related to exploring contribution of defects, both cation and anion vacancies in photoluminescence for multicolor photon emission has never been explored. Here, in this work, we have harnessed the full gamut of light emission from violet-blue to deep red originating from oxygen vacancies (OVs) in undoped CaSnO3 (CSO) and Eu@CaO8 and Eu@SnO6 sites in the doped CaSnO3:Eu3+ (CSOE) perovskite. Any contribution of Sn2+ and Eu2+, respectively, in photoluminescence of CSO and CSOE has been completely ruled out through X-ray absorption near-edge structure. Synchrotron radiation-based extended X-ray absorption fine structure and positron annihilation lifetime spectroscopy showed simultaneous distribution of Eu3+ ions at both asymmetric CaO8 and symmetric SnO6 sites owing to a very high negative formation energy value of −6.56 eV for the same. By efficient photon utilization arising from two different charge transfer bands, axial oxygen of SnO6 octahedra O1 → Eu3+ CTB (∼250 nm) preferentially transfers energy to Eu@CaO8 leading to intense electric dipole transition, whereas equatorial oxygen of SnO6 octahedra O2 → Eu3+ CTB (∼300 nm) excites Eu@SnO6 leading to intense magnetic dipole transition. This analogy is confirmed by DFT, wherein it was found that the calculated energy difference between the valence band maxima and conduction band minima is 4.77 eV (∼250 nm) and 4.3 eV (∼300 nm) for Eu@Ca and Eu@Sn sites, respectively. This concept of site-selective excitation and local site engineering can be applied to a variety of optical materials, which provides a unique strategy for tuning other properties of multifunctional crystals that are highly sensitive to the dopant’s local environment.

Skin entrance doses (SEDs) were estimated by carrying out measurements of air kerma from 101 X-ray machines installed in 45 major and selected hospitals in the country by using a silicon detector-based dose Test-O-Meter. 1209 number of air kerma measurements of diagnostic projections for adults have been analysed for seven types of common diagnostic examinations, viz. chest (AP, PA, LAT), lumbar spine (AP, LAT), thoracic spine (AP, LAT), abdomen (AP), pelvis (AP), hip joints (AP) and skull (PA, LAT) for different film-screen combinations. The values of estimated diagnostic reference levels (DRLs) (third quartile values of SEDs) were compared with guidance levels/DRLs of doses published by the IAEA-BSS-Safety Series No. 115, 1996; HPA (NRPB) (2000 and 2005), UK; CRCPD/CDRH (USA), European Commission and other national values. The values of DRLs obtained in this study are comparable with the values published by the IAEA-BSS-115 (1996); HPA (NRPB) (2000 and 2005) UK; EC and CRCPD/CDRH, USA including values obtained in previous studies in India.

The unique characteristics of the (W, N) dopant pair is that it reduces the band gap of NaNbO ₃ mainly by elevation of valence band maxima, which is very much crucial for photocatalyst for hydrogen evolution through water splitting.

in BHOE. Density functional theory studies of defect formation energy justified the same. Time-resolved emission spectroscopy showed distinct spectra for Eu@Ba and Eu@Hf sites corresponding to symmetric and asymmetric environments, respectively. This could be highly relevant in designing color tunable phosphor by forcing dopant ions at one specific site because Eu@Ba displayed orange emission whereas Eu@Hf displayed red emission. We could further harness BHOE for X-ray scintillator application by designing a thin film, which showed efficient conversion of high-energy X-ray into visible light. Under beta irradiation; both BHO and BHOE showed distinct TL glow curves as shallow traps were formed in the former and deep traps in the latter, which could have long-term implications in harnessing this material for persistent luminescence. We believe that BHO/BHOE demonstrated an extraordinary credential as a perovskite for multifunctional applications in the area of defect-induced light emission, UV phosphor, X-ray scintillator, and TL crystals.

The general order kinetics expression of thermoluminescence (TL) contains two empirical parameters, namely the kinetics order (KO) and the pre-exponential factor (PF). In this paper thermoluminescence glow curves are calculated by assuming well defined physically meaningful models and the KO and the PF values applicable to these glow curves are calculated. The approaches used to find these values are either analytical or based on the shape of the glow curves or their isothermal decay behaviour depending on the type of the model used. The results show that the KO and the PF parameters are in general not constant for a given glow peak. They vary with the change in occupancy of the traps except under the two limiting conditions, namely KO equal to 1 or 2. This means that, when the KO of a given glow peak is not equal to either 1 or 2, its numerical value as well as that of the PF would depend on the sample dose. It also means that these parameters change continuously when the glow curve is being recorded. At very low trap occupancies these parameters approach limiting values. For the simple one-trap model this limiting value of KO is 2 whereas that for a multi-trap model is 1. The corresponding changes in the quantitative values of the PF are by large orders of magnitude and the variation is in the direction opposite to that of the KO. Furthermore, the dimensions for the PF also change. These results bring the general order kinetics approach into conflict with the physical models used to describe the TL glow curves. Implications of these theoretical results for experimental observations are discussed.

The accelerating rate calorimetry studies on the tributyl phosphate and nitric acid reactions at various acid concentrations revealed that the conditions for red oil formation may vary with acid strength. The accelerating rate calorimeter studies supplemented with FT-IR characterization of the end products confirmed the formation of red oil at temperatures as low as 75 °C. This study thus strongly advocates for a revisit of safety limits set in the fuel reprocessing plants to prevent red oil formation. The chemical pathway for red oil formation is worked out.

Potassium tantalate (KTaO3) has emerged as a leading material for various industrial and technological applications owing to its excellent stability and electronic properties. In spite of extensive research conducted in the past decades, key defects in KTaO3 are still being investigated. In this study, a detailed systematic calculation using hybrid density functional theory has been carried out to investigate geometry, defect formation energies, and electronic properties of all possible neutral and charged intrinsic vacancy defects in KTaO3 under various growth conditions. We also extensively examine the role of a vacancy defect cluster in tuning the electronic properties of KTaO3. Furthermore, we elucidate the role of self-trapped electrons and holes and antisite defects in the optical properties of KTaO3, and thus a new perspective on the process of different intrinsic point defects in KTaO3 has been proposed. The formation energy calculation indicates that K-vacancy and its clusters will be readily formed in KTaO3 in all growth conditions, except under a K-rich environment. We find that O-vacancy, Ta-antisite, and K–O divacancy clusters are deep donors in KTaO3, while Ta-vacancy, K-antisite, and Ta–O divacancy clusters are deep acceptors. On the other hand, K-vacancy is a shallow acceptor in KTaO3, and K–O–K trivacancy clusters can act as both acceptors and donors. Based on analysis of formation energies and charge transition level, the present study reveals that O-vacancy, Ta–O, and K–O vacancy clusters mainly contribute to the prominent emission behavior of KTaO3 in the red–blue–green region. The present study provides critical insights into the microscopic picture of the optical behavior of KTaO3 perovskites. Thus, this study provides important guidelines for tuning the synthesis conditions to optimize functionalities based on different intrinsic vacancies.

Among different photocatalysts developed so far for the generation of hydrogen through water splitting, NaTaO 3 has been at the forefront due to its excellent stability and tunable electronic and optical properties. However, to extend its applicability to the range of visible light, the band gap has to be reduced significantly. In this study, we propose an efficient way to improve its visible light photocatalytic activity by doping with carbon in the presence of Cr, or Mo, or W. Although, monodoping with either C or Cr/Mo is able to reduce the band gap, the presence of localized defect states limits their applicability for photocatalytic purpose. This can be avoided by using dopant pair leading to formation of codoped systems. In the present study, two different types of codoped systems for each pair [(Cr, C), (Mo, C) and (W, C)] have been considered by varying the relative proportions of the dopant elements (1:1 and 2:1). Unfortunately, electronic structure analysis of 1:1 type of codoped systems show limitation similar to that of monodoped system. The advantage of 2:1 type of codoped system is that spontaneous formation of vacancy defects, which are efficient source for charge carrier recombination centers, can be minimum due to charge compensated nature. Besides, synthesis of 2:1 type of codoped system is found to be more feasible than the monodoped as well as 1:1 codoped system, as indicated by the formation energy calculation. Among the three 2:1 types of codoping, both (Mo, C) and (W, C) pairs lead to formation of favorable band structure with significantly reduced band gap (2.01 and 2.23 eV, respectively). The calculation of frequency dependent dielectric function has been carried out to get an idea about the shift in optical spectrum toward visible region due to codoping. Finally, the feasibility of water splitting involving the two codoped systems have been checked by aligning their band edge positions with respect to water redox levels.

Work hardening behaviour of P9 steel in the temperature range 300–873 K has been examined in the framework of Kocks–Mecking (K–M) approach. At all temperatures, P9 steel exhibited two-stage work hardening behaviour characterised by a rapid decrease in instantaneous work hardening rate (i.e. θ = d σ/d ϵ, where σ is the true stress and ϵ is the true plastic strain) with stress at low stresses (transient stage) followed by a gradual decrease at high stresses (stage III). Stage III work hardening of P9 steel was adequately described by K–M approach. The variations of work hardening parameters associated with K–M approach for stage III with temperature indicated three distinct temperature regimes. At all temperatures, good correlations between the respective work hardening parameters evaluated using K–M approach and from Voce equation and its derivative have been obtained for P9 steel.

The hydrodynamic parameters, namely, dispersed phase holdup and flooding throughput, have been investigated in 25 mm diameter pulsed disk and doughnut column (PDDC), in no mass transfer conditions. In this work, using existing correlations on plate pulsed columns, the dispersed phase holdup and the flooding throughput are empirically modelled well using the slip velocity concept. A good agreement is observed between experimental values and predicted values obtained from empirical correlation. The experimental data for dispersed phase holdup and flooding throughput has been modelled using the Van Delden model to describe the hydrodynamics characteristics of a PDDC and necessary adjustable parameters for drop size distribution and dispersed phase holdup are updated for 30% TBP-nitric acid system. The model parameters were estimated by minimizing the absolute error between experimental and theoretical values of flooding throughput and holdup data. It was found that the measured values and observed trends could be described accurately using this model after fitting holdup and flooding data. The error between the experimental and theoretical values of flooding throughput and holdup was found to be less than 10%.