[en] Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were conducted on self-irradiated as well as gamma irradiated BaCO₃ co-doped with ²³⁷Np⁴⁺ and NO₃^- ions. EPR studies of the irradiated samples revealed that the electron transfer process between iso-electronic carbonate and nitrate groups is the dominant effect of ionizing radiation, forming CO₃^- and NO₃^2- ions. This facilitated the radiation stability of the valence of Np in the tetravalent state. TSL spectral studies showed that Np⁴⁺ ion acts as the luminescence centre. TSL-EPR correlation studies revealed the role of CO₃^- ion in the glow peak at 413 K

[en] Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on cerium doped and cerium-uranium co-doped K₃Na(SO₄)₂ samples after γ-irradiation. Three glow peaks around 352, 415 and 475 K were observed and their spectral characteristics have shown that Ce³⁺ and UO₂²⁺ act as the emission centres in K₃Na(SO₄)₂:Ce and K₃Na(SO₄)₂:Ce, U, respectively. In Ce-U co-doped sample, energy transfer from cerium to uranium takes place. The commonly occurring radiation-induced centres in sulphates, viz SO₃^- and SO₄^- were observed by EPR and SO₄^- radical ion was found to take part in the TSL emission at 415 K. The hitherto unknown information, however, is the formation of SO₄^--SO₃^- radical pair creating deep traps in these lattices, apparently assisted by the dopants. This is the first observation of such radical pair formation leading to the identification of deep traps in this lattice. The radical pair, (SO₃^--SO₄^-) which is stable up to 970 K, decreases the intensity of the peak at 415 K due to the depletion of SO₄^- centres

[en] Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on samples of calcium chloro phosphate doped individually with UO²⁺₂ and ²³⁹Pu⁴⁺. TSL glow peak T_max around 135, 176, 190, 210, 435 and 490 K are observed with samples gamma-irradiated at 77 K. The trap depth and frequency factor for the prominent peaks are determined. EPR studies have revealed the formation of paramagnetic radicals PO^2-₄; O^-; O^-₂; (ClO)^2- and H⁰ under different conditions. From the spectral characteristics of the TSL glows and the thermal stabilities of the radical ions monitored using EPR the possible mechanism of the TSL glows are proposed. (author). 7 refs., 2 figs., 1 tab

[en] Electron paramagnetic resonance (EPR) evidence is presented for the radiation stabilization of pentavalent uranium in CaO matrix. From the theoretical predictions of g value for U⁵⁺ in axial symmetries, it was concluded that U⁵⁺ at Ca²⁺ site is associated with a second neighbour charge compensating Ca²⁺ vacancy. EPR measurements also revealed the presence of Mn²⁺, Mn⁴⁺ and Cu²⁺ impurities in the samples. The thermal stability of U⁵⁺ was investigated using EPR and thermally stimulated luminescence (TSL) techniques. The TSL and EPR studies on gamma irradiated uranium doped calcium oxide samples had shown that the intense glow peak at 540 K is associated with the reduction in the intensity of EPR signal of U⁵⁺ ion around this temperature. This peak is associated with the process U⁵⁺ + hole → U^6+* → U⁶⁺ + hv. The activation energy for this process was determined to be 1.4 eV. (author). 13 refs., 3 figs., 1 tab

[en] Thermally stimulated luminescence (TSL) studies of gamma irradiated uranium doped K₂Ca₂(SO₄)₃ revealed an intense glow peak around 400 K. Electron paramagnetic resonance (EPR) studies carried out on these samples have shown the formation of radical ions SO₄^-, SO₃^-, O₂^- and O₃^-. Of these, the thermal destruction of SO₄^- is found to be associated with the intense TSL glow around 400 K. The trap depth value for this peak has been determined from TSL and EPR data. (author). 4 refs., 2 figs., 1 tab

[en] Trap level spectroscopy studies of alkaline-earth sulphate (CaSO₄ and SrSO₄) phosphors doped with ²³⁹Pu were carried out using electron paramagnetic resonance (EPR) and thermally stimulated luminescence (TSL) techniques. Internal (in situ) α-irradiation (from the α-decay of ²³⁹Pu) and external γ-irradiation studies carried out using EPR revealed the formation of radicals SO₂^-, O^-, O₃^-, SO₄^-, etc, in these matrices under different conditions. SO₂^- dimer formation is detected for the first time in alkaline-earth sulphates on γ-irradiation at 77K. The thermal stabilities of the radical ions (monitored using EPR) and their correlation with TSL glow peaks helped to identify the thermally stimulated free-radical reactions which result in luminescence and were characterised by the activation energy and frequency factor obtained from the analysis of TSL glows. (author)

[en] Thermally stimulated luminescence (TSL) studies of gamma-irradiated uranium-doped K₂Ca₂(SO₄)₃ revealed two glow peaks around 400 K and 435 K. Electron paramagnetic resonance (EPR) studies carried out on these samples have shown the formation of the radical ions SO₄^-, SO₃^-, SO₂^- and O₃^-. From the study of the thermal stabilities of these radical ions, it was found that the thermal destruction of SO₂^- and SO₄^- radical ions are associated with the glow peaks observed around 400 K and 435 K respectively. Uranate ion was identified as the luminescent centre for the observed TSL glow. The trap depth values for the glow peaks have been determined from TSL data. (author). 19 refs., 4 figs

[en] The determination of impurities in plutonium/uranium at various stages of the nuclear fuel cycle plays an important role in quality control and the achievement of chemical and metallurgical requirements. Because impurities such as Cd, B and certain rare earth elements (Gd and Sm) are strong neutron absorbers, their concentration in nuclear fuel has to be maintained below certain limits. Increased concentration of other impurities may alter the metallurgical characteristics of the fuels, for instance strongly affecting the transition temperature between the different uranium/plutonium metal phases. AES methods based on d.c. arc-carrier distillation approach by far have served as the main workhorse in analytical spectroscopy of nuclear materials as it offers simultaneous multi-element determination, least handling of the sample and requires small sample size. The various methodologies developed in our laboratory for determination of trace metallic constituents in nuclear fuel materials such as PuO₂, (U,Pu)O₂, and ThO₂ are discussed

[en] Thermally Stimulated Luminescence (TSL) and Electron Paramagnetic Resonance (EPR) investigations were carried out on gamma irradiated strontium borophosphate (SrBPO₅) doped with CeO₂ and co-doped with CeO₂ and Tb₂O₃ samples. Apart from the hole trapped radical BO₃^2-, a few more radicals like O^- (g₁=2.0429, g₂=2.0195 and g₃=2.0016) and O₂^- or trapped electrons (g=1.9643) were formed on gamma irradiation at room temperature. The BO₃^2- radical was found to be stabilized at two different sites (site₁, g=2.0015 and A=8 G and site₂, g₁=2.0407, g₂=2.0139, g₃=1.9919, A₁=8.0 G, A₂=8.6 G, A₃=8.40 G). The EPR spectra recorded after annealing the irradiated sample at different temperatures showed that the radical ion O^- disappeared in the sample annealed at 475 K. It is proposed that the recombination between trapped electrons and O^- radical ion results in transfer of recombination energy to the doped Ce³⁺ ion resulting in TSL glow peak at 475 K. In case of co-doped samples energy transfer occurs between Ce³⁺ to Tb³⁺ resulting in increase in the intensity of glow peak at 475 K. (author)

[en] Electron paramagnetic resonance (EPR) and thermally stimulated luminescence (TSL) studies have been carried out in sub-room temperature region in γ-irradiated BaCO₃:²⁴¹Am phosphor. CO₂^- and CO₃^- radical ions are found to get stabilised at 77 K. Whereas CO₂^- radical was found to be stable upto room temperature. CO₃^- was found to get destroyed around 170 K coinciding with the occurrence of a TSL glow peak at that temperature. (author)