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  • Author or Editor: R. Acharya x
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Abstract  

A summary of k 0-based R&D work on neutron activation analysis (NAA), internal mono standard NAA (IM-NAA) and prompt gamma-ray NAA (PGNAA) is presented. The k 0-based NAA was standardized by characterizing irradiation sites of research reactors, validated using reference materials and applied to samples of different origin. Recently IM-NAA method was developed, validated for small and large size samples and applied for the analysis of large size as well as non-standard geometry samples. Studies on PGNAA included characterization of neutron beam, determinations of detection efficiency and prompt k 0-factors, and analytical applications.

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Abstract  

Instrumental neutron activation analysis (INAA) was employed to determine concentrations of 19 elements (As, Ba, Br, Ce, Co, Cr, Cs, Fe, K, La, Mn, Na, Nd, Rb, Sc, Sm, Th, Yb and Zn) in a large number (55) of tea samples (from market as well as virgin tea leaves) from different locations in India (Assam, Darjeeling, Munnar and Kangra). The results obtained in the present work are compared with those reported in literature. The concentration levels, their variations with collection locations and the correlations among different elements in these samples are discussed.

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Abstract  

Multielement analysis was carried out in two samples of natural rubies obtained from Kenya and Tanzania and a synthetic ruby obtained locally. The trace element profile was used to characterise the ruby samples. Instrumental Neutron Activation Analysis (INAA) by the single comparator (K 0 method) was used to determine the concentrations of 22 elements with gold as the comparator. High resolution -ray spectrometry was employed for radiometric assay of the activation products. The accuracy and precision were evaluated by analysing standard reference materials such as USGS-W-1 and AGV-1 and were found to be satisfactory.

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Abstract  

A study was conducted to estimate the thorium concentration in locally grown vegetables in high background radiation area (HBRA) of southern coastal regions of India. Locally grown vegetables were collected from HBRA of southern coastal regions of India. Thorium concentration was quantified using instrumental neutron activation analysis. The samples were irradiated at CIRUS reactor and counted using a 40% relative efficiency HPGe detector coupled to MCA. The annual intake of thorium was evaluated using the consumption data provided by National Nutrition Monitoring Board. The daily intake of 232Th from the four food categories (green leafy vegetables, others vegetables, roots and tubers, and fruits) ranged between 0.27 and 5.352 mBq d−1. The annual internal dose due to ingestion of thorium from these food categories was 46.8 × 10−8 for female and 58.6 × 10−8 Sv y−1 for male.

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Abstract  

A particle induced gamma-ray emission method using proton beam in conjunction with in situ current normalization approach was standardized for non-destructive determination of low Z element lithium and was applied for quantification of Li in lithium doped neodymium dititanate (Nd2Ti2O7) ceramic sample. Thick pellets of heat treated samples, their precursors and Li standards were prepared separately by homogeneously mixing with cellulose and fixed amount of F used for in situ current normalization. For validation of the method, four synthetic samples were also analyzed. Samples and standards were irradiated with 4 MeV proton beam (~5 nA current) from folded tandem ion accelerator (FOTIA) BARC, Mumbai. Characteristic γ-rays of 478 keV from 7Li to 197 keV from 19F were measured by high resolution γ-ray spectrometry. The Li concentrations determined in the six samples were in the range of 0.29–0.85 wt%. The Li contents in heat treated samples gave the idea about loss of Li compared to their precursors.

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Abstract  

In the Nawanshahr–Hoshiarpur region of Punjab, India, more than 1000 hectares of agricultural land is significantly affected by high levels of selenium (Se). Studies were carried out to examine Se levels in soil and crops such as wheat grains, wheat husk, rice, maize and mustard using neutron activation analysis. The Se concentrations in soil and crop products were found to be ranging from 2.7 to 6.5 mg kg−1 and 13 to 670 mg kg−1, respectively, indicating significantly high selenium in these crop products. Two reference materials were analysed for Se contents by INAA as controls.

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Abstract  

Three ferromanganese crusts from different locations of the Indian Ocean were analysed by neutron activation analysis using thek 0 method (k 0 NAA method) for studying the distribution of some trace elements along with Fe and Mn. Another crust from the Lau basin of the Pacific Ocean was investigated for comparison of the influence of different oceanic conditions on the trace element distributions in ferromanganese crusts. Variation in Co concentration along with the Mn/Fe ratio were discussed in terms of the hydrogenous/hydrothermal nature of the crusts. The normalised REE content was used to identify possible anomalies. The observed Ce anomaly is discussed in the light of the depositional environment. The precision and accuracy of the method were confirmed by measuring the elemental concentrations in a USGS nodule standard NOD A-1.

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Abstract  

For standardization of k 0-based instrumental neutron activation analysis, k 0-factors for short-lived nuclides (half-lives—11 s to 37 min) of elements F, Se, Sc, Al, V, Ti, Cu, Ca, Mg, I, and Cl with respect to gold (197Au) were determined using pneumatic carrier facility (PCF) at CIRUS reactor of BARC, Mumbai. Characterization of PCF was carried out by cadmium-ratio method using Au and Zr. The experimental k 0-factors of the isotopes were found to be in good agreement with the recommended k 0-factors in most of the cases, as evident from the values of % error and U-score at 95% confidence level. The method was validated by determining concentrations of elements through their short-lived nuclides in one type of the synthetic multielement standards (SMELS-I) obtained from SCK-CEN, Belgium. The method was also applied for determination of concentrations of some of the elements in two reference materials of IAEA, SL-3, and SL-1.

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Abstract  

Thorium along with its daughter products present in the soil is one of the major contributors to the external gamma dose in the environment. To establish the dose levels, quantification of thorium contents in soil samples is very important. As a part of pre-operational environmental radiological surveillance, a total of 23 soil and six sand samples were collected from different locations around the proposed nuclear power plant site of Jaitapur, Maharashtra. Thorium concentrations in these samples were determined by instrumental neutron activation analysis (INAA). Samples were irradiated with neutrons in Apsara reactor at a neutron flux of ~5 × 1011 cm−2 s−1 and radioactive assay was carried out using high resolution gamma ray spectrometry. Relative method of INAA was used for quantification of thorium utilizing 311.9 keV gamma ray of 233Pa, the daughter product of 233Th. The concentrations of thorium in the soil and sand samples were in the ranges of 4.0–18.8 and 1.2–6.2 mg kg−1 respectively.

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Abstract  

Barium borosilicate glass (BaBSG) is proposed as a potential candidate for vitrification of nuclear waste generated from thoria based nuclear reactors. Along with fission products, activation products and many inactive chemicals, like fluorine in the form of HF are expected to be present in the dissolver solution with nuclear waste. As vitrification occurs at high temperature, it is important to quantify fluorine in BaBSG. Due to its complex matrix, most of the wet chemical and nuclear analytical methods encounter problems in the estimation of fluorine. Particle induced γ-ray emission (PIGE) method has been standardized for non-destructive determination of fluorine contents in BaBSG samples utilizing measurement of prompt gamma-rays from 19F (p, p’γ) 19F reaction. Experiments have been carried out with thick pellet targets prepared in cellulose matrix using 4 MeV proton beam from the folded tandem ion accelerator at BARC, Mumbai. For obtaining current normalized count rate of interest, beam current variation was monitored by the Rutherford backscattering spectrometry (RBS) method as well as by the in situ approach using an externally added element sensitive to PIGE. In this paper standardization of PIGE methods for F determination, validation of methods using synthetic samples, and application to BaBSG samples are reported.

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