N L Misra
Articles written in Pramana – Journal of Physics
Volume 76 Issue 2 February 2011 pp 201-212 Invited Papers
Nuclear energy is one of the clean options of electricity generation for the betterment of human life. India has an ambitious program for such electricity generation using different types of nuclear reactors. The safe and efﬁcient generation of electricity from these reactors requires quality control of different nuclear materials, e.g. nuclear fuel, structural materials, coolant, moderators etc. These nuclear materials have to undergo strict quality control and should have different speciﬁed parameters for their use in nuclear reactors. The concentration of major and trace elements present in these materials should be within speciﬁed limits. For such chemical quality control of these materials, major and trace elemental analytical techniques are required. Since some of these materials are radioactive, the ideal chemical characterization techniques should have multielement analytical capability, should require very less sample (micrograms level) for analysis so that the radioactive waste generated, and radiation exposure to the detector and operator are minimum. Total reﬂection X-ray ﬂuorescence (TXRF) and energy dispersive X-ray ﬂuorescence (EDXRF) with improved features, e.g. application of ﬁlters, secondary target and instrumental geometry require very small amount of sample and thus can be suitably used for the characterization of nuclear materials mainly for the determination of elements at trace and major concentration levels. In Fuel Chemistry Division, TXRF analytical methods have been developed for trace element determinations in uranium and thorium oxides, chlorine determination in nuclear fuel and cladding materials, sulphur in uranium, uranium in sea water etc. Similarly, EDXRF analytical methods with radiation ﬁlters (to reduce background) and improved sample preapartion techniques, e.g. fusion bead and taking samples in the form of solution on ﬁlter papers have been used for developing analytical methods for the determination of U and Th in their mixed matrices, Cd in uranium etc. Some ofthese studies have been reported in this paper.
Volume 76 Issue 2 February 2011 pp 357-360 Contributed Papers
Uranium is reported to be present in phosphate fertilizers. The recovery of uranium from the fertilizers is important because it can be used as fuel in nuclear reactors and also because of environmental concerns. For both these activities suitable method of uranium determinations at trace levels in these fertilizers are required. Studies have been initiated for such TXRF determination of uranium and the results are reported in the present paper. For TXRF determinations the fertilizer samples were processed with nitric acid and the uranium present in it was removed by solvent extraction using tri-n-butyl phosphate as the extractant. The organic phase containing uranium was equilibrated with 1.5% suprapure nitric acid to bring out uranium in aqueous phase. This aqueous phase was mixed with internal standard Y and the TXRF spectra were measured by depositing samples on ﬂoat glass supports. The amounts of uranium in four fertilizer samples of Hungarian origin were determined by processing these TXRF spectra. Uranium concentrations in two fertilizer samples were found to be in the range of $4–6 \mu g/g$, whereas two fertilizer samples did not show the presence of uranium. The precision of the TXRF determination of uranium was found to be better than 8% ($1\sigma$).
Volume 76 Issue 2 February 2011 pp 361-366 Contributed Papers
Applicability of total reﬂection X-ray ﬂuorescence (TXRF) spectrometry for trace elemental analysis of rainwater samples was studied. The study was used to develop these samples as rainwater standards by the National University of Singapore (NUS). Our laboratory was one of the participants to use TXRF for this study. The rainwater sample obtained from NUS was analysed by TXRF and the trace elements Mn, Fe, Ni, Cu, Zn, V and Pb were determined as required by the NUS. The average precision was found to be within 16% and the TXRF-determined elemental concentrations of these elements were below $20 \mu g/l$. The average deviation of TXRFdetermined values from the certiﬁed values were 20% (excluding the deviation for Fe and V which were comparatively high). Apart from the above elements, S, K, Ca, Rb, Sr, Ba and Br were also determined by TXRF and were found to be in the range of 0.2 to 191 $\mu g/l$. TXRF-determined values of our laboratory played an important role in the certiﬁcation of concentration of seven elements in this rainwater sample which was later developed as a rainwater standard.