Results of a study of the corrosion of various transition-metal alloys, tantalum, and tantalum/2.5% tungsten are reported.
The solvent contained nitric acid, hydrofluoric acid, and ammonium hexanitratocerate. It was designed to imitate the corrosiveness
of the nitric acid, hydrofluoric acid mixture used to dissolve 238-plutonium dioxide.
Authors:N. Krasnov, Yu. Sevastyanov, I. Konstantinov, V. Vinogradova, and V. Malukhin
Procedures are described for determining traces of titanium in scandium, vanadium in titanium, zinc in copper and tungsten
in tantalum, utilizing activation with 11 Me V protons. Experimental data on48V,51Cr,66Ga and182Re yields and analytical sensitivities are reported.
A method is described to determine traces of V, Fe, Ni, Zn, Nb and Mo in high purity matrices of niobium, tantalum and tungsten
by non-destructive 14 MeV3He activation analysis. The influence of nuclear and γ-ray interferences in the determination of these elements is discussed.
The kinetics and mechanism of the dehydration and decomposition of heteropolyacids of molybdenum, tungsten and vanadium (H3+xYx+M12O40mH2O;
Y=Si, P; M=Mo, W) were studied. The data obtained on the dehydration kinetic parameters correlate with the expected structures,
of these crystal hydrates, the IR data and X-ray phase analysis.
Authors:K. Dadachova, K. La Riviere, and P. Anderson
Two improved processes of99Mo production have been developed on laboratory scale. The first one allows to purify Mo of natural isotopic composition from
tungsten impurities from 64 to <10 ppm by using preferential adsorption of tungsten on hydrated tin(IV) oxide (SnO2nH2O) before irradiation in a nuclear reactor. The second process deals with the separation of pure fission product99Mo from235U irradiated in a reactor. Two versions of separation process for production of fission99Mo have been developed. Both versions start with the dissolution of235U oxide target in nitric acid and are based on sequential use of alumina and anion exchange resin AG® 1-X8 columns. The yield
of99Mo in both versions is 80–89%.
A unique application of forensic neutron activation analysis involving the analysis of trace levels of tungsten, cobalt and
tantalum was presented as evidence in a murder trial. The evidence materials analyzed included the blous of the victim, bed
sheets, a pair of pantyhose used in strangulation, head and public hair from the suspect, and several samples of raw materials
used at a factory where the suspect was employed. The stalned areas of the fabrics analyzed showed trace levels of cobalt,
tantalum, and tungsten which were not present in the fabric mattrices. The occupation of the suspect exposed him to fine dust
particulates containing these trace elements. Although eyewitness accounts indicated that the suspect was in the neighborhood,
there was, however, no evidence other that the neutron activation analysis results to indicate the probable presence of the
suspect at the scence of the crime. A jury trial accepting neutron activation analysis findings resulted in a conviction.
In recent years chances of using rhenium-186 and rhenium-188 as radioactive isotopes in diagnostic and therapeutic applications
are increased very much due to the characteristic radiochemical and chemical properties of these two radioisotopes. In particular,
chemical similarities between99Tc and99mTc pair and186Re and188Re pair make it easier to correlate the two groups of compounds. Rhenium-188 is generated from the beta-decay of tungsten-188
which was produced by double neutron capture on enriched tungsten-186 oxide. It is of great interest to examine the impurities
in the eluate by radiochemical neutron activation. For this purpose, the preconcentration of the impurities in samples were
necessary, and it was achieved by adsorption on hydrated magnesium oxide.
Authors:A. M. Garrido Pedrosa, M. J. B. Souza, D. M. A. Melo, and A. S. Araujo
The thermo-programmed reduction study of Pt/WOx–ZrO2 materials prepared with different tungsten loading were performed by thermogravimetry. The samples were synthesized by impregnation method and calcined at 600, 700 and 800°C. The characterizations of both un-calcined and calcined materials were carried out using different techniques: thermal analysis (TG and DTA), X-ray diffraction (XRD) and thermo-programmed reduction (TPR). TG and DTA analysis of un-calcined were used to determination of calcination temperatures of the samples. XRD diffractograms were useful to help us in the determination of phase presents. TPR profiles showed between three and four events at different temperatures attributed to platinum reduction and the different stages of tungsten specie reduction.
Authors:I. Kikoin, S. Yakimov, N. Chernoplekov, V. Petrenko, K. Balashov, A. Knyazyatov, V. Gerasimov, V. Zenkevich, N. Tarasov, A. Malinin, M. Kozlova, V. Kharlamov, and N. Kurenkov
Highly enriched xenon124Xe /99.85%/ has been used for the experimental production of iodine123I by the /,n/ reaction. As the radiation source served a 30–45 MeV electron beam produced by a linear accelerator and converted by a tungsten converter to -radiation. The yield and radionuclidic purity of123I have been estimated, the content of isotopic impurities /124I and125I/ being for 30 MeV irradiations lower than 4×10–3%/.
The chemical aspects of isotopic fractionation in a multiple filament thermal ionization source were investigated. Samples
of uranium were loaded as nitrates, chlorides and sulphates. The dependence of measured isotopic ratios on the filament material
and the chemical form of the loading solution was studied. The dependence of the formation of uranium and its oxide ions on
various chemical and instrumental conditions were investigated using tungsten and rhenium filaments.