A scintillation method for determination of actinide alpha-activity in samples

This report describes an efficient, easy to use, and inexpensive method for detection of alpha-activity in biological samples, the alpha radiometer. The actinide elements are coprecipitated from acid-dissolved, ashed samples with bismuth phosphate and the precipitate is then mixed with ZnS(Ag) scintillation powder. The mixture is dried, in a thin layer, on the surface of a polystyrene cuvet and scintillations from the layer are detected with a photomultiplier tube. An optimal counting efficiency is obtained with a scintillation powder thickness between 25 and 40 mg·cm⁻².     

A new procedure for the spectrophotometric determination of uranium(VI) in the presence of a large excess of thorium(IV).

Spectrophotometric determination of microgram amounts of U(VI) with 2-(5-Bromo-2-Pyridylazo)-5-diethylaminophenol (Br-PADAP), originally developed by Johnson and Florence has been modified to enable the determination of U(VI) in the presence of a large excess of Th(IV). The effects of thorium, tri-n-butyl phosphate (TBP) and ethanol on the estimation of uranium have been studied in detail and are presented in this paper. This modified method can be applied for the analysis of U(VI) both in aqueous and organic samples containing a large excess of Th(IV) (Th:U = 10000:1).     

Experimental and theoretical studies of the products of laser-ablated thorium atom reactions with H2O in excess argon

Reactions of laser-ablated Th atoms with H2O during condensation in excess argon have formed a variety of intriguing new Th, H, O species. Infrared absorptions at 1406.0 and 842.6 cm-1 are assigned to the H-Th and Th=O stretching vibrations of HThO. Absorptions at 1397.2, 1352.4, and 822.8 cm-1 are assigned to symmetric H-Th-H, antisymmetric H-Th-H, and Th=O stretching vibrations of the major primary reaction product H2ThO. Thorium monoxide (ThO) produced in the reaction inserts into H2O to form HThO(OH), which absorbs at 1341.0, 804.0, and 542.6 cm-1. Both HThO(OH) and ThO2 add another H2O molecule to give HTh(OH)3 and OTh(OH)2, respectively. Weaker thorium hydride (ThH1(-4)) absorptions were also observed. Relativistic DFT and ab initio calculations were performed on all proposed molecules and other possible isomers. The good agreement between experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts provides support for these first identifications of Th, H, O molecular species.     

A titrimetric method for the sequential determination of thorium and plutonium

A method for the sequential determination of thorium and plutonium has been developed. In the sample solution containing thorium and plutonium, thorium is first determined by complexometric titration with EDTA and then in the same solution plutonium is determined by redox titration employing potentiometry. Prior to the determination of plutonium, EDTA is destroyed by fuming with concentrated HClO₄. Thorium is determined at 10 mg level and plutonium at 1 mg level with precision and accuracy of better than ±0.5%.     

A titrimetric method for the sequential determination of thorium and uranium

A method for the sequential determination of thorium and uranium has been developed. In the sample solution containing thorium and uranium, thorium is first determined by complexometric titration with ethylenediaminetetraacetic acid (EDTA) and then in the same solution uranium is determined by redox titration employing potentiometry. As EDTA interferes in uranium determination giving positive bias, it is destroyed by fuming with HClO₄ prior to the determination of uranium. A precision and accuracy of better than ±0.15% is obtained for thorium at 10mg level and uranium ranging from 5 mg to 20 mg in the aliquot.     

Isotopic fractionation of helium during solution: A probe for the liquid state

The isotopic fractionation of ³ He/ ⁴ He has been determined in pure H ₂ O, D ₂ O, seawater and two alcohols. The measurements have revealed the temperature dependence of the isotopic fractionation in each liquid. Substitution of D ₂ O for H ₂ O decreases the fractionation by a small but measurable amount. The fractionation varies with salinity and an equation is given for equilibrium values in seawater. The effect in ethanol is approximately 25% less than in water. Interpretation of the experimental results in terms of a zero-point-energy argument suggests that gas molecules dissolved in the different liquids occupy cavities with different sizes. In pure water the cavity size seems to be independent of the solute and is approximately 6 Å.     

Isotopic compositions of transuranic nuclides released by the Fukushima Dai-ichi Nuclear Power Plant accident: with emphasis on Cm isotopes

Isotopic composition of transuranic nuclides, with emphasis on Cm isotopes, were measured for environmental samples such as dust samples (black substances) from the roadsides and litter samples heavily contaminated by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Low levels of ²³⁸Pu, ^239,240Pu, ²⁴¹Am, ²⁴²Cm and ^243,244Cm were determined by α-spectrometry after radiochemical separation. These results, including radioactive Cs, provided an isotopic data set. When the activity ratios among these transuranic nuclides were compared with those of core inventories (Units 1–3) in the FDNPP estimated by the JAEA group, fairly good agreement was found, indicating that traces of transuranic nuclides, probably in the forms of fine particles, were released into the environment without their large fractionations. The obtained data may lead to more accurate information about the on-site situation (e.g., burn-up, conditions of fuel during the release phase, etc.), which would be difficult to receive otherwise, and on the dispersion and deposition processes of transuranic nuclides and the behavior of these nuclides in the environment.     

A neutron-activation scheme developed for the determination of 42 elements in lunar material

A neutron-activation scheme designed for the determination of 42 elements in lunar rocks and fines is described. The scheme is based on seven different irradiations, four of which are followed by direct gamma-spectrometry, and three by radiochemical separation systems. The total sample consumption for duplicate analysis is about 800 mg. The scheme has been tested on basalt BCR-1, and results for this standard rock are presented. Analytical experience obtained from analyses of lunar samples and BCR-1 is discussed.     

A never-ending search for the truth: Thermodynamics in the uncertain era of the internet

This article is based on the 20th Rossini Lecture delivered on 28 July 2014 at the opening of the 23rd International Conference on Chemical Thermodynamics in Durban, South Africa.In the last several decades, enormous progress in material and computer sciences has led, in many scientific disciplines, to fundamental improvements in experimental measurement technologies. That, in combination with new communication technologies and gradually increasing societal commitment to support public scientific research, has resulted in an unprecedented growth in the “production” of the reported experimental results. These trends together with dramatically growing demand for thermophysical and thermochemical property data related to new chemical processes and products necessitated development of dynamic methods of critical data evaluation within a framework of the concept of Global Information Systems in Science which was developed and implemented for the field of thermodynamics at the Thermodynamics Research Center (TRC) of the US National Institute of Standards and Technology (NIST). Principal advantages of this approach in comparison with the traditional static methods of critical data evaluation are illustrated.Major components of the developed system and its impact on such areas of human activities as information delivery, data publication, chemical process design, chemical product design, experiment planning, and education are discussed. The systems and software tools designed for global validation of experimental values are outlined. A variety of experimental data-driven technologies for thermophysical property prediction developed with the use of the elements of the Global Information System in Thermodynamics, including those based on surrogate mixture models, group contributions, QSPR, UNIFAC, and Monte Carlo molecular simulation, are described.     

A path integral influence functional for excess electron in fluids: Density-functional formulation

In this paper, we propose a path integral influence functional from a solvent to determine a self-correlation function of a quantum particle in classical simple fluid. It is shown that the influence functional is related to a grand potential functional of the pure solvent under a three-dimensional external field arising from a classical isomorphic polymer, on which the quantum particle is mapped. The influence functional can be calculated from the self-correlation function, the solute-solvent and the solvent-solvent pair correlation function. The obtained equation of the self-correlation function is applied to an excess electron problem in fluid helium. The Fourier path-integral Monte Carlo method is employed to perform the path integral of the electron. The solute-solvent pair correlation function is estimated from a reference interaction site model integral equation. These results obtained form our proposed influence functional and from that proposed by Chandler, Singh, and Richardson are compared with those provided by a path integral Monte Carlo simulation with the explicit helium solvent.     

A spectrophotometric method for the determination of thorium with acid alizarin black Sn

Acid alizarin black SN reacts with thorium at pH 4.2 to give a highly sensitive colour reaction with thorium, ε₆₀₀ mμ = 28,000. There is no interference from Ba, Ca, Cd, Ce(III), Gd, Hg, La, Mg, Mn, Pb, Pr. Sm, Sr, Zn, Zr, Cl(su-), CN(-), I(su-), NO(3-), SO₄^2-. The interferences of Al, Bi, Co, Cu, Fe, Ni, Mo, Sb, Sn, Ti and W may be overcome by addition of masking agents. Only U(VI) and V(V) still interfere and these can be determined sequentially with the thorium. The nature of the complex is studied and the mode of its formation.     

A sequential radiochemical procedure for isotopic analysis of uranium and thorium in soil

A sequential radiochemical procedure for isotopic analysis of uranium and thorium in soil has been developed. Analysis involves total dissolution of the samples to allow equilibration of the natural isotopes with added tracers, followed by radiochemical separation using anion exchange chromatography (BioRad AG 1–X8). Further separation and purification is performed employing solvent extraction techniques. Finally, the U and Th fractions are co-precipitated with lanthanum and cerium fluoride, respectively, and quantified by alpha-particle spectrometry. Overall chemical yields range from 60 to 90%. Under normal operating conditions and present counting set up, the minimum detectable concentration (MDC) is approximately 2 Bq/kg for soil samples. This is based on one gram aliquot of sample, 80% chemical yield, and 1000 minute counting with a detector having about 15% counting efficiency. The procedure has been successfully tested with Standard Reference Materials. Various soil samples were analyzed with high chemical yields and fine quality of alpha-spectra. Decontamination factor studies were performed to determine the extent of the carry over of²¹⁰Po,²²⁵Ac,²²⁶Ra, and²²⁹Th into U fraction and²¹⁰Po,²²⁵Ac,²²⁶Ra, and²³²U into Th fraction.     

A method for the purification of bulk amount of thorium from its daughter products

A method has been developed to purify bulk amounts of natural thorium from its daughter products. The method is based on anion exchange separation of Th from Pb, Bi, Tl, Ra using Dowex 1 X 8 anion exchange resin conditioned to 2M HCl. The method has several advantages over other methods, namely the decontamination is quite high, Th separation is quantitative and it is suitable for the purification of bulk amounts of Th in a reasonably short time.     

A new method for determination of thorium in solution by X-ray fluorescence technique

A method of thorium determination in aqueous solutions is described using X-ray fluorescence technique. Experimental and theoretical saturation values have been calculated for thorium analysis. The¹⁰⁹Cd∶Ge(Li) system was used in the study. Effects of escape peak of Ge(Li) detector have been corrected by using the Compton peak of blank spectra. Therefore, X-ray spectra have been normalized in order to evaluate the net thorium spectrum and to increase the sensitivity of analysis.     

A simple method for the determination of uranium and thorium by delayed neutron counting

A simple method for the determination of uranium and thorium by delayed neutron counting is described. One portion of the sample is irradiated in a reactor and the delayed neutrons are counted. Another portion of the sample is mixed with B₄ C powder absorbing the thermal neutrons, and irradiated in the same position. From those data, both uranium and thorium can be calculated when a quantitative calibration has been made beforehand. The detection limits for the pure elements are 0.07 ppm for uranium and 2 ppm for thorium with the minimum analyzing time being 2 min. The accuracy of the method is investigated by comparing results obtained by the method described here with results obtained by epithermal activation analysis.     

A search for a β effect: the nucleophilicity of the methylene glycolate anion

The possible existence of a β-effect (effect of a lone pair of electrons located at a β position of a nucleophile) was investigated by reacting méthyléne glycolate anion with p-nitrophenyl acetate, 2,4-dinitro-fluorobenzene and 2,4-dinitrochlorobenzene in water. For these reactions, no enhanced nucleophile reactivity was found. An upper limit of 2.5 was found for the nucleophilicity n of méthyléne glycolate on the Swain-Scott scale and 6.2±0.2 on Ritchie's N₊ scale.     

An interpretative model for the anomalous behavior of some excess properties in mixed liquid systems: a relationship between excess molar volumes and excess compressibilities in strongly self-aggregated fluids

A simple theoretical model based on the hole theory of the liquid state has been developed in order to find a relationship between the excess molar volume and the excess compressibility of a two-component fluid. The model has been extended to investigate strongly associating fluids dissolved in an apolar solvent. Such a model nicely explains our recent results obtained from a Brillouin scattering study of the nonideal mixture between tert-butyl alcohol and 2-2(') dimethyl butane. Its validity, however, seems to be rather general and it could be usefully applied to rationalize the excess properties of several nonideal binary fluid mixtures.     

A neutron activation analysis procedure for the determination of uranium,thorium and potassium in geologic samples

A neutron activation analysis procedure was developed for the determination of uranium, thorium and potassium in basic and ultrabasic rocks. The three elements are determined in the same 0.5-g sample following a 30-min irradiation in a thermal neutron flux of 2·10¹² n·cm^?2·sec^?1. Following radiochemical separation, the nuclides²³⁹U (T=23.5 m),²³³Th (T=22.2 m) and⁴²K (T=12.36 h) are measured by β-counting. A computer program is used to resolve the decay curves which are complex owing to contamination and the growth of daughter activities. The method was used to determine uranium, throium and potassium in the U. S. Geological Survey standard rocks DTS-1, PCC-1 and BCR-1. For 0.5-g samples the limits of detection for uranium, throium and potassium are 0.7, 1.0 and 10 ppb, respectively.