Ch. Gopal Reddy

Baseline studies of radon/thoron concentration levels in and around the Lambapur and Peddagattu areas in Nalgonda district, Andhra Pradesh, India

Abstract Studies conducted by Atomic Minerals Directorate of Exploration and Research (AMD) of Hyderabad, India had established the presence of higher concentrations of uranium in Lambapur and Peddagattu areas of Nalgonda district, AP, India and it was estimated that it could be a viable source for commercial extraction. The envisaged extraction process involves dispersion of radioactive particulate matter into atmosphere. Environmental radioactive studies in and around proposed mining areas at this point of time will be extremely useful for establishing base line data before a large scale uranium extraction process comes into existence. To this end, Solid State Nuclear Track Detectors were installed to evaluate indoor radon and thoron concentration levels in the dwellings of the area. The geometric means of radon and thoron concentration levels were found to be (7.1±0.2)×101 and (6.7±0.3)×10 1 Bq / m 3 , respectively. Simultaneously, natural background radiation measurements were also made and these levels are found to vary from 770 to 3995 μGy / y in the spatial distribution.

Thermoluminescence characteristics of Sm3+ doped NaYF4 crystals

Thermoluminescence (TL) characteristics of NaYF4 crystals doped with Sm3+ have been studied after γ-ray irradiation. Dependence of luminescence efficiency on Sm3+ concentration and radiation dose has been measured and possible applications of NaYF4: Sm3+ as a novel phosphor for TL dosimetry have been investigated. The efficiency of 0·3 mole% Sm3+ doped NaYF4 crystal has been found to be maximum and comparable with commercial thermoluminescence dosimetric (TLD) materials.

Nanosize effects in Eu doped La0.67Ca0.33MnO3 perovskite

Electrical, magnetic and Mossbauer measurements have been carried out on La0.67−xEuxCa0.33MnO3 (x=0.21 and 0.29) for a comparative study of different grain size materials. The samples have been prepared through sol–gel method and sintered at 700, 800, and 900 °C to achieve nanosized materials. All the prepared samples are found to be single phase having orthorhombic structure. The particle sizes are estimated through x-ray diffraction (XRD) by using the Debye–Scherrer’s formulae and these sizes are further confirmed by transmission electron microscopy (TEM) images. E151u Mossbauer studies reveal that Eu is in 3+ charge state. The isomer shift and full width at half maximum (FWHM) of the Mossbauer peak decrease with the increase in particle size. Reduction in the grain size leads to drastic increase in electrical resistivity in all the samples. The typical metal–insulator transition (MIT) observed in x=0.21 bulk sample disappears with decrease in grain size while an external magnetic field of 8T restores t...

Role of plastic deformation in thermally stimulated luminescence of KBr crystals containing yttrium

Our aim is to identify the nature of defects which play a dominant role on thermally stimulated luminescence process

Magnetic, ferroelectric, and spin phonon coupling studies of Sr3Co2Fe24O41 multiferroic Z-type hexaferrite

The magnetic, Raman, ferroelectric, and in-field 57Fe Mossbauer studies of polycrystalline multiferroic Sr3Co2Fe24O41 are reported in this paper. From the magnetization studies, it is observed that the sample is soft magnetic in nature with low temperature magnetic spin transitions like longitudinal to transverse conical structure around 130 K and change in magnetic crystalline anisotropy from conical to planar structure at 250 K. Ferroelectric studies of the sample exhibit the spontaneous polarization at low temperature. Strong spin phonon and spin lattice coupling is observed through low temperature Raman spectroscopy. From the in-field 57Fe Mossbauer spectroscopy, spin up and spin down site occupations of Fe ions are calculated in the unit cell.

Environmental radioactivity studies in the proposed Lambapur and Peddagattu uranium mining areas of Andhra Pradesh, India

The present work was aimed at the establishment of baseline radioactive data in the proposed Lambapur and Peddagattu uranium mining areas in the Andhra Pradesh state, India. The background concentrations of naturally occurring radioactivity in the near-surface soils of the study areas were estimated and the results were analysed. The (238)U concentration in the near-surface soil of the study area was found to vary from 100 to 176 Bq kg(-1), with a mean of 138±24 Bq kg(-1). (232)Th in the study area soils was found to vary between 64 and 116 Bq kg(-1), with a mean of 83±15 Bq kg(-1). The (40)K concentration was found to vary between 309 and 373 Bq kg(-1), with a mean of 343±20 Bq kg(-1). The mean natural background radiation levels were also measured with thermoluminescence (TL) dosimetry technique and with a µR-survey meter, in the villages of the study area. Dose rates measured by TL are found to vary from 1287 to 3363 μGy y(-1), with a mean of 2509 ± 424 μGy y(-1). The dose rates measured in the same villages with a μR-survey meter were found to be in the range of 1211-3255 μGy y(-1), with a mean of 2524 ± 395 μGy y(-1). The mean radiation levels in the study area are found to be relatively high when compared with (Indian) national and international averages. Correlations among radon, thoron and gamma dose rates were found to be poor. The pre-operational data produced in this work will be useful for comparison with future radiation levels during the proposed uranium mining operations.

Airborne radioactivity levels in dwellings of Khammam district, Andhra Pradesh, India

Abstract Radon/thoron levels are estimated in Khammam district as a part of “Radon/thoron mapping” program in Andhra Pradesh, India. About 100 dwellings were chosen at random covering most parts of Khammam district. Twin chamber cup dosimeters consisting of solid-state nuclear track detectors (SSNTDs, LR-115, Type-II) were used to evaluate the radiation levels at quarterly intervals for a period of one calendar year. The average radon and thoron concentrations were found to be 39.1±13.3 and 19.4±14.9 Bq / m 3 , respectively. Seasonal variations of radon/thoron levels were also studied. Variations of radon/thoron concentration levels with different types of dwellings have been studied. In the bare flooring dwellings thoron levels were found to be highest in comparison to concrete, limestone and marble floorings.

Study of indoor radon and its progeny concentration levels in the surrounding areas of Hyderabad, Andhra Pradesh, India

Abstract Having studied the radon/thoron and their concentration levels in the urban Hyderabad (known for higher concentrations of uranium, thorium and 40 K compared to other metropolitan cities of India), an attempt has been made to measure radon and its progeny levels in its surrounding areas covering the region beyond municipal limits, with an approximate radius of 50 km , using the technique of solid-state nuclear track detectors. The concentration levels of radon and its progeny varied from 3 to 47 Bq / m 3 and 0.04 to 3.5 mWL with arithmetic mean of 11 Bq / m 3 and 0.9 mWL , respectively. These airborne radioactivity levels in the surrounding areas of Hyderabad are found to be less than the activity levels of urban Hyderabad region. Seasonal variations of these activity levels have also been studied. Further, variation of radon and its progeny levels in different types of dwellings were investigated and it is found that the dwellings with bare flooring and mud walls were found to have higher concentration levels. Distribution of dwellings for different radon levels was carried out to unravel the effect of poor ventilation, type of the construction materials used, etc.

Pre- and post-irradiation deformation effects on the thermoluminescence of KCl:Y crystals

Abstract The thermoluminescence (TL) behaviour of X-irradiated KCl crystals containing yttrium have been investigated as a function of plastic deformation, both prior to and subsequent to irradiation. In the crystals subjected to deformation prior to irradiation, the TL intensity is found to increase with the amount of plastic deformation whereas in those subjected to deformation subsequent to irradiation, the same is observed to decrease. A new high temperature glow peak is also found to grow due to the plastic deformation before irradiation. These results are explained on the basis of various processes of point and line defect interactions; such as creation, modification and annihilation of traps by moving dislocations, etc.; that take place during the plastic deformation of the crystal.

Effect of plastic deformation on the thermally stimulated luminescence of NaCl:Y crystals

Abstract The relation between plastic deformation and thermally stimulated luminescence (TSL) in NaCl crystals doped with yttrium has been studied in some detail. Plastic deformation followed by irradiation in these crystals caused the increase in TSL intensity and a shift in peak positions of peak II (70°C) and peak III (130°C) to high temperatures. The defects playing the dominent role in shifting the TSL peaks on deformation are identified. The shifting of peaks to high temperatures on plastic deformation is attributed to the perturbation at the emitting sites caused during the redistribution of defect centres on deforming the crystal.