The thermal behaviour of the hexamminechromium hexafluorometallates and [Cr(NH3)6]F3. HF·H2O was investigated by non-reciprocal quasi-isobaric thermal analysis, X-ray diffraction and i.r. spectroscopy. Reduction of
chromium(III) was not observed, neither during the decomposition [Cr(NH3)6]F3·HF·H2O nor during the decomposition of any of the title hexamminechromium hexafluorometallates. Obviously this reduction is not
promoted by the coordinative Cr−N bonds, neither these in the starting materials nor those in the intermediately formed phases.
Under non-reciprocal quasi-isobaric conditions, hexamminechromium hexafluorometallates are ideal precursors for preparing
mixed cationic fluorides both in the rhombohedral modification and in the modification of the hexagonal tungsten bronze type
Authors:S. Landsberger, M. S. Basunia, and S. Schroit
We have determined nineteen trace elements in 685 aerosol filter samples collected during 1964-1978 in northern Finland by the Finnish Meteorological Institute. In this paper we present some procedures and results for very short (~25 s), short (~3-54 min), and medium (12-35 h) lived isotopes as determined by epithermal NAA in conjunction with and without Compton suppression. Elements with a Iγ/σthratio are favorable to be determined by epithermal NAA. Silver was determined by a one minute epithermal irradiation because of a very short 110Ag half-life. Antimony, arsenic, cobalt, bromine, indium, iodine, potassium, silicon, tin, tungsten, and zinc were determined by a ten minute epithermal irradiation. For silver determination, samples were counted without transferring the filter from the irradiated vial, however, for ten minute irradiation all samples were transferred to a non-irradiated vial and counted both in the normal and Compton mode by the HPGe gamma-spectrometry system with a decay time of about 10 minutes and counting time of 15 minutes. Each day a maximum of 16 samples were irradiated and immediately following the short counting, these samples were loaded into an automatic sample changer in sequence of irradiation and counted for an hour in both normal and Compton modes. This has proven to be an extremely cost effective measure thus reducing the need to employ long-lived NAA to analyze other elements such as Ag, Co, Sn and Zn and Ag for air pollution source receptor modeling.
Authors:M. Pillon, M. Angelone, P. Batistoni, R. Forrest, and J.-Ch. Sublet
The fusion reactor inventory code FISPACT, together with the European Activation File EAF, is the European reference software for calculating the neutron-induced activation of fusion reactor relevant materials. Experimental verifications (benchmarks) of the code predictions have been performed at ENEA Frascati by means of an irradiation facility consisting of a D-T neutron generator and a moderator/reflector structure which is employed to mimic the neutron spectrum at the a fusion device first wall. Various materials (vanadium alloy, SiC, AISI 316, martensitic steel F82H, copper, tungsten, iron, niobium), candidates to be used in a fusion reactor, have been exposed to neutrons produced in the facility (about 109 n cm–2 s–1) and the short and medium-lived induced radioactivity has been measured by gamma-ray spectroscopy. The experimental results have been used to validate the inventory code FISPACT, the physical database EAF, including its uncertainty predictions, and the composition of the material irradiated in particular for its minor elements and impurities. The comparison between calculated (C) and experimental results (E) is reported as C/E values and shows a satisfactory agreement for almost all radionuclides. Radionuclides for which there is not agreement between calculations and experiments are also discussed and an analysis of the causes of the lack of agreement is carried out.
We are seeking to extend the capabilities of an in vivo XRF system which was originally designed for the exclusive detection of Fe in skin. Our interest concerns development of a more versatile in vivo XRF diagnostic facility for measurement of Fe and Zn. Elevations of these two elements have been noted to occur in a number of skin disorders and ailments. The XRF system comprises a high-output tungsten anode X-ray tube, the collimated exit beam of which is made to impinge on an appropriate choice of filter. The present study makes use of a beam hardening filter in place of our previous use of a K-edge filter. Operating at 15 kVp, 23 mA, and using a Mo beam hardening filter of 0.2 mm thickness, we have obtained a quasi-monoenergetic output of approximately 13 keV and full-width at tenth maximum (FWTM) of 1.4 keV. Preliminary measurements on simulated skin indicate that we are able to detect Fe, Zn and Cu, at levels of the order of 20-, 10- and 5 g (g skin tissue)–1, respectively, using monitoring periods of the order of 2000 seconds, and skin entrance doses of less than 16 mSv.
Solvent extraction of Cr(VI), Mo(VI), W(VI) and Hf(IV) with 1-phenyl-3-methyl-4-caproyl-pyrazolone-5 (PMCP) in methyl isobutylketone
(MIBK), xylene and chloroform (CHCl3) from mineral acid solutions was studied. Chromium(VI) is not extracted from any of the acids studied (HCl, H2SO4 and HClO4). Molybdenum(VI) is quantitatively extracted by the reagent in xylene and CHCl3 from HClO4 and HNO3 solutions. It is also extracted quantitatively by the reagent in MIBK from HCl, HNO3 and H2SO4 solutions but the participation of the diluent as extractant is considerable. Tungsten(VI) is quantitatively extracted in
xylene from 9M HClO4 solution. MIBK used as diluent also affects its extraction with PMCP. Hafnium(IV) is not extracted from H2SO4 solutions while it extracts more than 99% at 3M HNO3 and above. The extracted species likely are: MoO2(PMCP)2, WO2(PMCP)2 and Hf(PMCP)4, respectively.
Authors:Md. Rahman, Kyung-Sook Kim, Manwoo Lee, Guinyun Kim, Youngdo Oh, Hee-Seock Lee, Moo-Hyun Cho, In Ko, Won Namkung, Van Nguyen, Duc Pham, Tien Kim, and Tae-Ik Ro
We measured isomeric-yield ratios for the 197Au(γ,n)196m,gAu reactions with bremsstrahlung energies of 50-, 60-, 70- MeV, and 2.5-GeV at the two different electron linac of the Pohang
accelerator laboratory by using the activation method. The photons were produced when a pulsed electron beam hit a thin tungsten
target. The well-known photoactivation method was used and hence the induced activities in the irradiated foils were measured
with the high-resolution γ-ray spectrometric system consisting of lithium drifted high-purity Germanium detector and a multichannel
analyzer. The measured isomeric-yield ratios for the 197Au(γ,n)196m,gAu reactions were (4.95 ± 0.51) × 10−4, (5.72 ± 0.72) × 10−4, (6.03 ± 0.50) × 10−4, and (9.27 ± 0.83) × 10−4 for 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies, respectively. The present results measured with the bremsstrahlung
energy higher than 60-MeV are the first measurement.
Improved radionuclide generator include a substantially insoluble salt of a radioactive parent which may be directly packed
in column for subsequent elution of the daughter radionuclide. An improved 188Re generator was prepared by reacting a radioactive tungsten (188W) as parent radionuclide incorporated with aluminum chloride to obtain an insoluble radioactive aluminum tungstate matrix.
The investigated matrix was characterized on the basis of the chemical composition, IR, thermal analysis and mechanical stabilities.
The factors affecting the elution performance were studied such as influence of pH, molar ratio and drying temperature. From
the obtained data, the molar ratio W:Al was 1.5:1 at pH = 4, the matrix dried at 105 °C for 2 h. Chromatographic and multichannel
analysis has been currently used to investigate the radiochemical and radionuclidic purity respectively on eluted 188Re. An elution yield more than 80%, with radiochemical purity <98% and radionuclidic purity <99% with a 188W break through >10−4% of the column. The Al+3 and W contents value were about 2 and 3 μg/mL eluate. The obtained data approved the stability of the prepared generator
and its suitability for medical application.
Authors:T. Green, S. Biegalski, S. O’Kelly, and G. Sayre
Stainless steel flux wires were used to determine the neutron energy spectra and total flux during the Reactor Accelerator
Coupling Experiments (RACE) at The University of Texas at Austin. A LINAC electron accelerator produced 20 MeV electrons at
a power of 1.6 kW, which struck a tungsten-copper target to produce bremsstrahlung radiation and photoneutrons. The neutrons
produced in the target were multiplied by the subcritical core of a Triga reactor. The purpose of the RACE experiments is
to develop a sub-critical accelerator driven system that would be capable of transmuting actinides from spent fuel. Flux measurements
were made with 1.58 mm diameter stainless steel wires placed throughout the core between the fuel rods and cadmium covered
and uncovered gold and indium foils above the target. The MAXED and GRAVEL computer codes were used to perform the spectrum
unfolding. The composition of the stainless steel wires was determined using neutron activation analysis with comparators
prior to the flux measurement. The reactions measured in the stainless steel to determine the flux were 50Cr(n,γ)51Cr, 58Ni(n,p)58Co, 54Fe(n,p)54Mn, and 58Fe(n,γ)59Fe. Flux measurements agreed well with an MCNP simulation of the experiment.
A radiochemical neutro activation analysis procedure has been developed for the determination of sodium and potassium at parts
per billion levels in high purity tungsten/titanium alloy material. The procedure involves the use of an anion exchange separation
for purifying sodium and potassium activities from the alloy’s matrix activities,46Sc and187W. In addition, the use of two sequential sample loadings on the resin column prior to elution of the matrix activities has
been investigated. Irradiation of 200 mg of the alloy results in a sample of nearly 1 Ci which must be handled in a remote
manipulation cell. After acid dissolution of the sample, the sample solution in 1M HF was loaded onto the column. Elution
of the sodium and potassium was accomplished using 40 ml of 1M HF. Similar loading and elution of the second sample was followed
by the elution of matrix activities with a solution of 1M HF+6M HCl. Extensive tracer experimentation was employed to establish
the possibility of retaining the matrix activities on the column while a second sample solution was processed, thus greatly
increasing the throughput in terms of the number of samples analyzed per day. The detection limits of Na and K using the method
developed are 4.0 ppb and 200 ppb, respectively.
Authors:V. Malyshev, M. Shiryaeva, Z. Sokolova, L. Lyubimova, Yu. Salmin, M. Tatarkin, K. Ryumina, and A. Shelyakina
Data on the applicability of neutron activation analysis to determine various rare and trace elements and the isotopic abundance
of some of them in natural samples are discussed as relevant to the solution of various geological and geochemical problems.
For the determination of minute amounts of elements from small weighed quantities of rocks and minerals a number of modifications
of neutron activation analysis are used: analysis with the radiochemical separation of individual elements—RNAA (tantalum,
tungsten, antimony, arsenic, molybdenum, rhenium, osmium, etc.) and analysis with semiconductor—Ge (Li)—gamma-spectrometry,
which is multi-element and non-destructuve—INAA (scandium, europium, tantalum, iron caesium, rubidium, cobalt, antimony, etc.)
or the combination of the latter with group radiochemical separation—IRNAA (alkaline, alkaline-earth, rare-earth elements,
etc.). First steps have been made towards developing techniques for the determination of the isotopic rations of some elements
by means of neutron activation method, e.g., the isotopic ratio of58Fe/54Fe. The accuracy of isotopic ratio determination is 1 to 3 relative per cent.