Compact fluorescent lamp phosphors in accidental radiation monitoring.

The application of lamp phosphors for accidental dosimetry is a new concept. Since the materials used in fluorescent lamps are good photo luminescent materials, if one can either use the inherent defects present in the phosphor or add suitable modifiers to induce thermoluminescence (TL) in these phosphors, then the device (fluorescent lamp) can be used as an accidental dosemeter. In continuation of our search for a suitable phosphor material, which can serve both as an efficient lamp phosphor and as a good radiation monitoring device, detailed examination has been carried out on cerium and terbium-doped lanthanum phosphate material. A (90)Sr beta source with 50 mCi strength (1.85 GBq) was used as the irradiation source for TL studies. The TL response as a function of dose received was examined for all phosphors used and it was observed that the intensity of the TL peak vs. dose received was a linear function in the dose range 0.1-200 Gy in each case. Incidentally LaPO(4): Ce,Tb is a component of the compact fluorescent lamp marketed recently as an energy bright light source. Besides having very good luminescence efficiency, good dosimetric properties of these phosphors render them useful for their use in accidental dosimetry also.

Chemical separation and ICP-AES determination of 22 metallic elements in U and Pu matrices using cyanex-923 extractant and studies on stripping of U and Pu.

Comprehensive studies have been carried out on the extraction behavior of uranium and plutonium matrices using cyanex-923 extractant. The near total extraction of U/Pu and quantitative separation of 22 metallic elements at trace levels has been established using inductively coupled plasma-atomic emission spectrometry (ICP-AES). The studies carried out on back extraction of U/Pu from organic phase have established the near total recovery of these matrices into the aqueous phase using 1 M Na(2)CO(3) and saturated oxalic acid, respectively.

Atomization mechanism and determination of Ag, Be, Cd, Li, Na, Sn and Zn in uranium-plutonium matrices by ETA-AAS.

The atomization processes involved in the Electrothermal Atomization-Atomic Absorption Spectrometric (ETA-AAS) determination of Ag, Be, Cd, Li, Na, Sn and Zn in the presence of an uranium-plutonium matrix containing 25% Pu have been investigated. The significant fall in the absorbance signal for Ag, Cd, Na and Zn in an uranium matrix and its restoration in the presence of plutonium is probably correlated with the change in the partial pressure of oxygen released from the matrix at/below the signal appearance temperature (T(app)). In case of Li and Sn, the signal remains unaffected irrespective of the U-Pu matrix which might be due to a high T(app) for these analytes. Regarding Be, the steep suppression of the signal in the presence of the plutonium matrix compared to an uranium matrix can be ascribed to the formation of stable Pu-Be compounds (PuBe(13)). Based on these studies, analytical procedures have been developed for the direct determination of nanogram amounts of these analytes in an U-Pu matrix with an average precision of 9% RSD.

ICP-AES determination of silver after chemical separation from uranium matrix.

The separation of silver from a uranium matrix has been carried out using Cyanex-471X (triisobutylphosphine sulphide) in xylene. The effects of various parameters such as the Cyanex-471X concentration, the nitric acid molarity, the contact time and the nitrate ion concentration on the extraction of silver have been studied. The silver metal ion species extracted into the organic phase was found to be Ag(NO(3)).2S (where S is Cyanex-471X). The stripping of silver into an aqueous medium was carried out with 5% NaHSO(3), followed by its determination using ICP-AES.

Direct determination of beryllium, copper and zinc in AlU matrices by electrothermal atomization atomic-absorption spectrometry.

An atomic-absorption spectrometric method with electrothermal mode of atomization has been developed for the direct determination of Be, Cu and Zn in AlU (3:1) matrix samples without prior chemical separation of the major matrix. The studies carried out include the effect of the matrix on the analyte absorbance, optimization of sample aliquot and other experimental parameters, and analysis of a number of synthetic samples. Nanogram amounts of the analytes can be determined with a solution aliquot of 5 microlitres containing 25 micrograms of the sample with a precision of 6% or better. The analytical range obtained for these analytes is Be: 2-20 mug/l., Cu: 20-200mug/l. and Zn: 1-40mug/ml in the AlU matrix. The analysis of synthetic samples has shown good agreement with their added contents.

Trace metal assay of U(3)O(8) powder by electrothermal AAS.

Methods have been developed for the direct determination of Ag, Ca, K., Li, Mg, Na, Pb, Sn and Zn in U(3)O(8) powder samples by electrothermal AAS. Nanogram and lower amounts of these elements have been determined with a relative standard deviation of 6-16% in mg amounts of sample (either alone or mixed with an equal weight of graphite). The results for NBL reference samples were in reasonable agreement with the certified values. X-Ray diffraction studies on the residues left from the graphite mixtures after the atomization cycle, confirmed the formation of uranium carbide (UC(2)).