X-Ray spectrometric methods for the determination of plutonium and uranium in their mixed oxide samples

An X-ray fluorescence binary ratio method to measure non-destructively the relative percentage of PuO₂ in (U, Pu)O₂ samples is described. Calibration lines for pellet and microsphere samples are established and evaluated. Independent X-ray measurement of the major component after dissolution leads to the determination of individual concentrations within ±0.5% rel. of the chemical values.     

Synthesis and luminescence investigation of RE (Eu, Tb and Ce)-doped lithium silicate (Li2SiO3)

Synthesis and photoluminescence (PL) investigations of lithium metasilicate doped with Eu³⁺, Tb³⁺ and Ce³⁺ were carried out. PL spectra of Eu-doped sample showed peaks corresponding to the ⁵D₀→⁷F_j (j=1, 2, 3 and 4) transitions under ultraviolet excitation. Strong red emission coming from the hypersensitive ⁵D₀→⁷F₂ transition of Eu³⁺ ion suggested the presence of the dopant ion in structurally disordered environment. Tb³⁺-doped silicate sample showed blue-green emission corresponding to the ⁵D₄→⁷F_j (j=6, 5 and 4) transitions. Ce-doped sample under excitation from UV, showed a broad emission band in the region 350-370 nm with shoulders around 410 nm. The fluorescence lifetimes of Eu³⁺ and Tb³⁺ ions were found out to be 790 and 600 μs, respectively. For Ce³⁺, the lifetime was of the order of 45 ns. PL spectra of the europium- and terbium-doped samples were compared with commercial red (Y₂O₃:Eu³⁺) and green (LaPO₄:Tb³⁺) phosphors, respectively. It was found that the emission from the doped silicate sample was 37% of the commercial phosphor in case of the Tb-doped sample and 8% of the commercial phosphor in case of the Eu-doped sample.     

Synthesis,TGA and EPR studies of phase transitions in Cu2+ doped (NH4)4ThF8 and (NH4)3ThF7

The paper presents the EPR evidence for the occurrence of phase transitions in (NH₄)₄ThF₈ and (NH₄)₃ThF₇. In both cases the Cu²⁺ probe occupies a NH⁴⁺ site and predominantly experiences a dynamic coordination, either due to dynamic Jahn-Teller effect, or due to fluxional behaviour of surrounding (ThF₈)^4- units in (NH₄)₄ThF₈. It is proposed that the structural phase transition in this compound at 214 K is associated with the transition of the dynamic coordination of Cu^2- into a static one, probably due to freezing of motion of (ThF₈)^4- units below this temperature. In (NH₄)₃ThF₇ the dynamic features of the Cu²⁺ EPR spectrum are absent and characteristics of a local orthorhombic symmetry are seen down to 77 K. However, in the high temperature range a change from orthorhombic to axial symmetry is observed at 524 K, possibly due to a phase transition.     

Microwave-assisted Claisen rearrangement of naphthyl 2-propynyl ethers: synthesis of naphthofurans

An efficient two-step approach for the synthesis of naphtho[1,2-b]furans and naphtho[2,1-b]furans has been developed. Various functionalized propargyl alcohols were etherified with α- or β-naphthol under Mitsunobu reaction conditions to give naphthyl 2-propynyl ethers, which underwent a facile microwave-assisted Claisen rearrangement and concomitant anionic cyclization to yield naphthofuran derivatives under basic reaction conditions.     

X-ray,Thermal and Infrared Spectroscopic Studies on Potassium,Rubidium and Caesium Uranyl Oxalate Hydrates

M₂UO₂(C₂O₄)₂⋅nH₂O compounds (M=K, Rb and Cs)have been prepared and characterized by chemical and thermal analyses as well as by X-ray diffraction and infrared spectroscopy. X-ray powder data show that the compounds belong to an orthorhombic system. Thermal and infrared studies show that the compounds decompose to M₂UO₄ through the formation of alkali metal carbonate and UO₂ as intermediates. K₂UO₂(C₂O₄)₂⋅3H₂O, and Rb₂UO₂(C₂O₄)₂⋅2H₂O gave K₂UO₄, Rb₂UO₄ at 700 and 600°C respectively, while in the case of Cs₂UO₂(C₂O₄)₂⋅2H₂O, the intermediate products of decomposition reacted to yield Cs₂U₄O₁₃ at 1000°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermoluminescence and linear thermal expansion of MgAl2O4

The co-efficient of linear thermal expansion (α _av) and dose dependence of thermoluminescence (TL) in MgAl₂O₄(s) were measured. The change in length per unit length was recorded as a function of temperature between room temperature to 1,273 K at a heating rate of 8 K min^?1, in flowing argon atmosphere. The average of three measurements was quoted as the α _av for MgAl₂O₄(s). The linear thermal expansion was measured to an accuracy of ±3 %. The dose dependence of the TL was found to be super linear in the dose range of 0–10 kGy with a k value of 0.503 indicating that the MgAl₂O₄(s) ceramic is ideally suited for the dose estimation of self-irradiated inert matrix fuel in a once through fuel cycle for actinide burning.