Hafnium, determination separation from

Analyses of alloys or ores for hafnium by plasma emission atomic absorption spectroscopy, optical emission spectroscopy (qv), mass spectrometry (qv), x-ray spectroscopy (see X-ray technology), and neutron activation are possible without prior separation of hafnium (19). Alternatively, the combined hafnium and zirconium content can be separated from the sample by fusing the sample with sodium hydroxide, separating silica if present, and precipitating with mandelic acid from a dilute hydrochloric acid solution (20). The precipitate is ignited to oxide which is analy2ed by x-ray or emission spectroscopy to determine the relative proportion of each oxide. 

Hafnium, determination of, in zirconium-hafnium solution, 3 69 extraction of, from cyrtolite and separation from zirconium, 3 67, 74... 

Many [M(dik)4] complexes are volatile, especially those that contain fluorinated diketonate ligands. Mass spectra and gas chromatographic behavior of several of these complexes have been studied (see Table 10). Isenhour and coworkers240 241 have employed fluorinated diketonates in mass spectrometric procedures for determination of Zr and Zr/Hf ratios in geological samples. The most intense peak in mass spectra of [M(dik)4] complexes is [M(dik)3]+. Sievers et al.242 have used gas chromatography of metal trifluoroacetylacetonates to separate Zr from Al, Cr and Rh. However, attempts to separate [Zr(tfacac)4] and [Hf(tfacac)4] by gas chromatography were unsuccessful. Zirconium and hafnium can be separated by solvent extraction procedures that employ fluorinated diketones.105 [M(dik)4] (M = Zr or Hf dik = acac, dpm, tfacac or hfacac) have been used as volatile source materials for chemical vapor deposition of thin films of the metal oxides.243,244... 

In the optimization of conditions of hafnium extraction from tributylphosphate (TBF), these factors were analyzed X,-concentration of nitric acid in outlet water solution, [N] X2-concentration of TBF in e-xylol, % X3-ratio of phases, [1] and X4-time of extraction, min. The coefficient of hafnium separation was determined as the system response. 1/2-replica of full factorial experiment 24 (X4=X3X2X3) was chosen as the basic experiment. The outcomes of the experiment are given in Table... 

The presence of uranium in a sample exposed to a flux of thermal neutrons can cause errors if the nuclide or nuclides determined are fission products or are isotopic with them. Hudgens and Dabagian (39) determined zirconium in zirconium-hafnium mixtures by separating the Nb , daughter of Zr formed by n,y reaction, after the addition of carrier. Contributions from fission product niobium (Nb ) can be allowed foi by irradiating a further sample, isolating fission product Ba ° and from the fission yield curve making allowance for radioactive niobium derived from any uranium impurity. 

Enriched UF is shipped to the plant for fabricating reactor fuel elements in monel cylinders whose size is determined from the content, so as to prevent accumulation of a critical mass. At the fuel fabrication plant UF is converted to UO or other chemical form used in reactor fuel. For light-water reactors the UOj is pressed into pellets, which are sintered, ground to size, and loaded into zircaloy tubing, which is filled with helium and closed with welded zircaloy end plugs. These individual fuel rods are assembled into bundles, constituting the fuel elements shipped to the reactor. Conversion of UFj to UO2 is described in Chap. 5. Extraction of zirconium from its ores and separation of zirconium from its companion element hafnium is described in Chap. 7. 

In designing multistage extraction systems for extractive separations by TBP, or by other extractants that can change appreciably in noncomplexed concentration as a result of extraction, it is necessary to perform analyses similar to Eq. (4.1 S) through Eq. (4.24) for each of the extractable species present in other than trace quantities to determine the distribution coefficients for each of the species in each of the contacting stages [G6, H2, L3]. Such design procedures are illustrated in Sec. 6.6 for the separation of hafnium from zirconium by TBP extraction from a nitric acid solution. 

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