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Abstract  

The electrochemical behaviour of PrF3 was studied in the LiF–CaF2 (79/21 molar ratio) at 1,213 K. Inert (W) and reactive (Ni) electrodes were used. Pr(III) ions are reduced in a single, three electron exchange. The redox potential of the Pr(III)/Pr couple at the inert electrode was observed very close to the decomposition potential of the LiF–CaF2 melt. Experiments using reactive working electrode were done. The results show the potential shift connected to the alloying reactions of Pr and Ni. Deposition of Pr–Ni layer was confirmed by SEM-EDX analysis. Conclusions for the Pr separation possibilities from spent nuclear fuel were done.

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Abstract  

A study of the electrochemistry of uranium in LiF–BeF2 system important for molten salt reactor concept was conducted at W and Ni electrodes. Cyclic voltammetry and chronopotentiometry methods were used. Two-step reduction mechanism for U4+ ions involving one electron exchange in soluble/soluble U4+/U3+ system and three electron exchange in the second step were found on W electrode. Both processes were identified as reversible and diffusion-controlled. Based on voltammetric and chronopotentiometric measurements, the diffusion coefficient of U4+ ions at 813 K was calculated: D(U4+) = 1.26 × 10−6 cm2 s−1 and D(U4+) = 1.28 × 10−6 cm2 s−1, respectively. Formation of U–Ni alloys was observed on Ni electrode.

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Abstract  

A mixture of equal quantities of powdered LiF and NaF was doped with 0.2% each of Ti, Mg and Mn and heated to obtain a LiF+NaF phosphor. After grinding and sieving, the thermoluminescent phosphor was used to obtain the thermoluminescence characteristics such as the glow curve; the dose-response curve, sensitivity, reproducibility and linearity were all established. The main goal was to introduce two new methods for the calculation of trap energy: the single-peak-differential and single-peak-integration methods, both modifications of the basic method of Randall-Wilkins. The plots used to calculate the trap energy were In[(dα/dT)1/(1-α)]vs. 1/T and ln[ln(1-α)/(T o-T)]vs. 1/T, respectively. These linear plots with slopes of (E/k) gave trap energies ofE=0.547 eV andE=0.551 eV, respectively.

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Interesting effects of fluoride additives, LiF, NaF and CaF2, on the solid-state reactions in the MgO - Cr2O3 and ZnO - Cr2O3 systems under an atmosphere of nitrogen were observed by means of DTA. For the MgO Cr2O3 - MF (M=Li, Na) systems, it was concluded that the melting of the fluoride additives plays an important role in accelerating the second reaction step at around 1000°. On the other hand, for the ZnO- Cr2O3 - MF (M=Li, Na) systems, a great acceleration by the additives was observed in the first reaction step at around 700°, a much lower temperature than the melting points of the fluorides. The effect of CaF2 was not clear in either system.

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Abstract  

The solubilities of lanthanum oxide in LiF, NaF, KF and eutectic melt LiF-NaF-KF (46.5 mole% LiF; 11.5 mole% NaF and 42.0 mole% KF) were measured in order to find the suitable electrolyte for electrodeposition of lanthanum. Solidus-liquidus lines were obtained by the method of thermal analysis. The solubility of lanthanum oxide in alkali fluorides is rather low and decreases in the order LiF>NaF>KF. It was found that lanthanum oxide reacts with the components of the melt. LaOF and alkali metal oxide are formed during dissolution of La2O3 in the melt.

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A model describing the initial step of diffusion-controlled solid-solid reactions is presented. The kinetic equation obtained was used to evaluate the activation energy of the reaction LiCl(s)+NaF(s)=LiF(s)+NaCl(s) from DTA data.

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Abstract  

Laser-induced fluorescence (LIF) coupled with photon-counting technique to detect molecular iodine at ultratrace level is reported. Electronic quenching rate constants for N2, NO2 and H2O, as well as for the mixture of NO2 and H2O has been measured. The application of the LIF method to monitoring129I2 in spent fuel reprocessing off-gas streams is evaluated.

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Abstract  

Different combination of raw materials and nucleating agents were incorporated in the batch of nepheline-pyroxene glass to demonstrate their effect on the crystallization process. The effect of TiO2, Cr2O3 and LiF with respect to crystallization of base glass was studied by differential thermal analysis (DTA).These materials improved the crystallization of glass between 50 to 150C of heat treatment. When LiF+TiO2 and TiO2+Cr2O3 were put together in the glass batches, the rate of crystallization of glass was increased in the same manner. The presence of TiO2+LiF+Cr2O3 improved the crystallization of the glass by decreasing the heat temperature by about 60C. CaO/MgO and CaO/Na2O ratios played an important role in the rate of crystal growth. The increase in the CaO/MgO ratio lowers the crystallization temperature by values ranging between 37 and 46C.

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Abstract  

An accurate and precise wavelength dispersive X-ray fluorescence spectrometric method is described for the quantitative analysis of hafnium impurities in zirconium oxide matrix in the range from 6.8 to 1004 g/g, using the HfL 1 line on 8420+ XRF Quantometer (ARL) with LiF (220) crystal and scintillation detector. The practical limit of measurement is 6.8 g/g. The precision is between 1 to 6% for higher and lower concentrations of hafnium, whereas accuracy in most cases is <5%.

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Abstract  

Thermoluminescence and optical properties of LiF:Mg,Cu,P; BaSO4:Dy; BaSO4; Eu and α-Al2O3:C were investigated as a part of a broader research project on TL mechanisms in various materials. The effects of ionizing radiation on these phosphors are determined in this work by means of thermoluminescence and optical absorption experiments with the aim of identifying new defects formed in these systems and of testing dosimetric characteristics.

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