The use of nuclear recoil for producing radioactive endohedral and cage-labeled fullerenes is presented, with special emphasis on the energy of chemical effects after nuclear particle capture. The different possibilities using (n,), (n,), (p,n), (g,n) and (,n) and (,n) nuclear reactions are treated in detail.
In chemical processing technology on-line activation methods gain an increasing importance for process monitoring and control.
In the paper presented a method is described according to which the different fluorspar contents at various strategic points
of a flotation plant are to be determined through neutron activation by 100 μg252 californium. For that purpose, a continuous analytical system for on-stream process control of slurries was designed and
constructed. This SUSAC compact facility allows continuous application of the method on an industrial scale.
The principles of selective separations by recrystallization are explained and formulae for the calculation of decontamination
factors are presented. Experiments with strontium sulfate and radioactive strontium ions demonstrate the validity of the theoretical
considerations. Similar or higher decontamination factors are found than those calculated for a uniform distribution of the
radioactive strontium ions between crystals and solution. The high values are explained by assuming a recrystallization mechanism
which consists of dissolution and redeposition of crystal layers. The half-times of recrystallization increase sharply with
Sr2+ or SO
concentration in the solution. In nitric acid solutions as well as in mixtures containing nitrates and nitric acid the solubility
of strontium sulfate is rather high, accordingly the decontamination factors are low under these conditions and furthermore
the recrystallization half-times are long.
The determination of α- and pure β-emitting impurities in99Mo/99mTc generator eluates before application is discussed. It is shown that α-emitters in ≥10 mCi eluates can be determined in
a proportional counter or an α-spectrometer within 30 min with detection limits lower than the European Pharmacopoeia limit
(10−7% of the main activity).89Sr and90Sr are determined after chemical separation, consisting of ion exchange to separate the main activity (TcO
), shaking with charcoal to separate colloidal particles containing Mo and precipitation of Sr as oxalate or sulfate. The
precipitate is measured in a low-level counter. For eluates with an activity of ≥10 mCi the detection limits are one order
of magnitude lower than the activity limit given by the European Pharmacopoeia for90Sr (6×10−6% of the main activity). The time needed for chemical separation and activity measurement is about 30 min.
Evidence is obtained to show that the liquidliquid extraction separation of99mTc from99Mo with methyl ethyl ketone, methyl propyl ketone and methyl isobutyl ketone can be transformed into a solid-phase column extraction procedure. The aqueous alkaline99molybdate solution is immobilized on a column of a granular large-pore diatomaceous earch support, which is the neluted with the abovementioned extractants. Rapid and clean separation of99mTc can be with all three solvents. The99mTc can be back-extracted from the organic phase on a column filled with distilled water /or saline/ loaded granular diatomaceous earth /Extrelut®/. The possibility of using the abovementioned procedure as a basis for a new99mTc/99Mo generator concept is envisaged.
Authors:G. Braun, G. Boden, K. Henkel, and H. Rossbach
The direct nitridation of different silicon powders was investigated by thermogravimetry. The chemical composition of the final product, produced unter the optimum nitridation conditions, varied in the region between Si3N3.41 and Si3N3.93, depending on the basic material. The reasons for the incomplete nitridation ratio are discussed.
Authors:T. Braun, H. Rausch, L. Bíró, Z. Konya, and I. Kiricsi
By using instrumental neutron activation analysis (INAA) it has been shown that some pristine carbon SWNT's and MWNT's of
different makes, contain a multitude of trace element impurities at various concentration levels including also amounts which
can be considered as nanoelectronically dopant quantities. The same holds for the above mentioned carbon nanotubes also after
their inadequately so-called purification.
Authors:H. Vogg, H. Braun, R. Löffel, A. Lubecki, A. Merz, J. Schmitz, J. Schneider, and J. Vehlow
The works done by the “Laboratorium für Isotopentechnik” of the Nuclear Research Centre, Karlsruhe, is discussed in the field
of the application of radioisotope techniques in chemistry and chemical engineering.