D. Alamelu

Laser-induced breakdown spectroscopy for simultaneous determination of Sm, Eu and Gd in aqueous solution

This paper reports studies on the determination of trace levels of samarium, europium and gadolinium in aqueous samples by laser-induced breakdown spectroscopy (LIBS). In this work, a membrane-based filter paper was used as a sample support for the liquid samples. The laser-induced plasma was produced in air at atmospheric pressure, using a pulsed Nd:YAG laser. Calibration standards and synthetic mixtures of these lanthanides were prepared using solutions prepared from respective high purity oxides. Linear calibration was obtained for Sm, Eu and Gd by normalizing the intensities of lanthanides emission lines with respective to C(I) 193.029 nm emission line. The concentrations of Sm, Eu and Gd were then determined in a solution containing a mixture of these lanthanides. The concentrations of individual lanthanides were obtained within 5% of the expected values. Limits of detection were found to be 1.3 ppmw (Sm), 1.9 ppmw (Eu) and 2.3 ppmw (Gd).

Determination of thorium and uranium in solution by laser-induced breakdown spectrometry

Laser-induced breakdown spectrometry (LIBS) has been successfully developed to quantify thorium (Th) and uranium (U) in solution using membrane-based filter paper as a sample support. The filter paper is easy to handle and the entire analysis process takes only a few minutes for each sample. The developed method provides a practical approach for fast and sensitive determination of actinides in aqueous solutions using LIBS. We obtained calibration curves for U and Th individually as well as as a mixture. We observed that the quantification of trace levels of U in a bulk amount of Th was not possible because of strong spectral interference from Th at the most intense lines of U, but traces of Th in a bulk amount of U could be determined. The concentrations of U and Th in unknown solutions were determined by use of LIBS, and these results agreed to within 4% and 2%, respectively, with the expected values. The limits of detection for Th and U were calculated from the experimental data and were in the range of a few parts per million by weight to a few tens of parts per million by weight.

Laser-induced breakdown spectroscopy for determination of uranium in thorium-uranium mixed oxide fuel materials.

Laser-induced breakdown spectroscopy (LIBS) has been developed for determining the percentage of uranium in thorium-uranium mixed oxide fuel samples required as a part of the chemical quality assurance of fuel materials. The experimental parameters were optimized using mixed oxide pellets prepared from 1:1 (w/w) mixture of thorium-uranium mixed oxide standards and using boric acid as a binder. Calibration curves were established using U(II) 263.553 nm, U(II) 367.007 nm, U(II) 447.233 nm and U(II) 454.363 nm emission lines. The uranium amount determined in two synthetic mixed oxide samples using calibration curves agreed well with that of the expected values. Except for U(II) 263.553 nm, all the other emission lines exhibited a saturation effect due to self-absorption when U amount exceeded 20 wt.% in the Th-U mixture. The present method will be useful for fast and routine determination of uranium in mixed oxide samples of Th and U, without the need for dissolution, which is difficult and time consuming due to the refractory nature of ThO(2). The methodology developed is encouraging since a very good analytical agreement was obtained considering the limited resolution of the spectrometer employed in the work.

Laser induced breakdown spectroscopic quantification of platinum group metals in simulated high level nuclear waste

LIBS has been developed for the quantification of platinum group metals (PGM), namely Pd, Rh and Ru in simulated high level liquid nuclear-waste (SHLLW) samples to provide an alternative analytical approach to other techniques. Calibration curves were obtained using high purity solutions of the individual PGMs and were validated using the individual PGM solutions as well as their mixtures. The amounts of the PGMs present in SHLLW both in the presence and in the absence of uranium were determined. The results agreed well with the expected values when the concentration of uranium was up to 700 ppmw, while positive bias was observed in the presence of larger amounts of uranium (above 700 ppmw). For such samples, satisfactory agreement of the results with those of the expected values was obtained after extraction of uranium with tributylphosphate.

Laser induced breakdown spectroscopy for rapid identification of different types of paper for forensic application

The goal of this work was to examine the probability of instant identification of confidential documents for forensic application by comparison with a spectral library generated using laser induced breakdown spectroscopy (LIBS). The library consisted of representative spectra from different types of papers used for official (governmental) work. Statistical methods using linear and rank correlations were applied to identify the unknown paper. Both correlation methods yielded probabilities of correct identification close to unity for all the studied samples. The approach would have applications in forensic science.

Analysis of barium borosilicate glass matrix for uranium determination by using ns-IR-LIBS in air and Ar atmosphere

Abstract In this paper, an attempt to explore the use of laser induced breakdown spectroscopy (LIBS) technique for determination of uranium in the vitrified simulated high level barium borosilicate waste glass matrix was made with a commercial portable LIBS system. The emission spectrum of the waste glass being very complex, detailed study was done for proper choice of the emission lines. Investigations were carried out to optimize the experimental parameters like laser energy and acquisition delay time for the analysis. Calibration curves were obtained for two emission lines of U in these glasses. Effect of Ar atmosphere was also studied and the signal intensity was found to be ∼5 times higher than in air atmosphere The emission lines used for normalization with vast difference in the upper energy level compared to the line of interest were found to give poor precision in air. In the Ar atmosphere, this effect was found to be much less significant and such emission lines can be used as an internal standard to achieve precise calibration curves. LIBS approach will be useful for real time determination of U in such samples, eliminating quantitative dissolution step required in many other analytical techniques like solution based ICP-MS/OES.

Isotope dilution gamma spectrometry for Pu using low energy photons

Abstract Isotope dilution gamma spectrometry (IDGS) for determination of the Pu concentration, using high resolution gamma-ray spectrometry (HRGS) in the 40–150 keV energy range, is developed and described. The methodology involves purification of Pu by an anion exchange procedure, followed by the determination of Pu isotopic composition using HRGS. For isotope dilution, a pre-calibrated power reactor grade Pu (∼ 70 at. % 239Pu) solution from an Indian PHWR was used as a spike for research reactor grade Pu (∼ 95 at. % 239Pu) samples and vice versa. Changes in 240Pu/239Pu (45.24 keV/51.62 keV) and 241Pu/239Pu (148.57 keV/129.29 keV) activity ratios in the spiked samples were determined by gamma spectrometry. Using the atom ratios calculated from the measured activity ratios, the concentration of Pu in the sample was calculated using two different efficiency calibration methods. The isotopic composition and concentration of Pu samples both from power reactor and research reactor grade agreed well with the values obtained by isotope dilution-thermal ionization mass spectrometry. The present method also shows the superiority of using the 240Pu/239Pu atom ratio against the 241Pu/239Pu atom ratio in IDGS with respect to the accuracy and precision.

A critical evaluation of different isotope correlations for the determination of 242Pu

Different correlations are evaluated for the determination of (242)Pu in Pu generated from PHWR reactors with an average burn-up of about 10,000 MWd/TU. It is shown that the correlations involving ratios of Pu isotopes, except for (241)Pu, provide data with better confidence compared with those involving the atom% abundance. These correlations are also attractive when the decay period of the given sample is not known. In addition, it is shown that instead of using (239)Pu atom% abundance alone (Swinhoe et al., 2010), either (240)Pu atom% or a linear combination of (239)Pu and (240)Pu gives abundance of (242)Pu with better reliability. The uncertainty due to different decay periods also remains unaffected when using the correlation involving both (239)Pu and (240)Pu atom%. The present conclusions are based on Pu isotopic composition data from PHWR reactors ((239)Pu 65-75%) whereas those reported by other investigators are for PWR and BWR types of reactors.

Determination of 235U/238U atom ratio in uranium samples using liquid scintillation counting (LSC)

A correlation has been developed for the determination of (235)U/(238)U atom ratio in uranium samples using liquid scintillation counting (LSC). The (235)U/(238)U atom ratio determined by thermal ionization mass spectrometry (TIMS) was correlated to the ratio of (i) alpha-count rate and (ii) Cerenkov count rate due to (234 m)Pa in the sample; both measured by LSC. This correlation is linear over the range of (235)U/(238)U atom ratio encountered in the nuclear fuel samples, i.e. the low enriched uranium (LEU) samples with (235)U<20 atom%. The methodology based on this correlation will be useful for the quick determination and verification of (235)U/(238)U atom ratios in fuel samples using cost effective technique of LSC.

Gas phase reactions of uranyl with α-hydroxyisobutyric acid using electrospray ionization mass spectrometry and density functional theory

Electrospray ionization mass spectrometry (ESI-MS) technique was used to find out the type of species of uranyl with α-hydroxyisobutyric acid in positive and negative ion modes. It was found that the singly charged monomeric and doubly charged dimeric species were present in soft ionization conditions. The molecular level understanding on the structures and energetics were investigated using density functional theory based calculations. It was found that ML3, the most intense species observed in ESI-MS were energetically more favorable as compared to ML1 and ML2.