[en] Humic and fulvic acid can be combined under the term 'humic substances' and are natural substances with a complex structure. The structural details are not known, however, due to the functional groups present in these compounds the formation of hydrogen bonds is easily attained. Several humic substances were investigated for their potential use as compounds, which are applicable for tritium enrichment from aqueous solution. For comparison a simple compound, malonic acid, representing only few functional groups was investigated. The experiments were performed using a cryosublimation apparatus, which was run well below equilibrium vapor pressure to avoid any isotope fractionation of HTO and H₂O. A higher enrichment factor was found for natural humic acid compared to fulvic acid, however, no enrichment could be found for a synthetic humic acid and malonic acid. Interpretation of the results is difficult since no detailed information on the chemical structure of humic substances is known

[en] Now that the discovery of all elements in the 7th period has been announced, has the far end of the Periodic Table of the Elements been reached? What is the heaviest element in the Periodic System? Are there still undiscovered ones which might even be found in nature? Is there an 8th period and how many elements will it contain? Will we need to introduce the g-orbitals and will the current principles governing the groups and periods of the Periodic Table still be valid for the heaviest elements? These intricate questions are the topic of current research in fundamental nuclear chemistry. (author)

[en] With the recent synthesis of superheavy nuclides produced in the reactions ⁴⁸Ca+²³⁸U and ⁴⁸Ca+^242,244Pu, much longer-lived nuclei than the previously known neutron-deficient isotopes of the heaviest elements have been identified. Half-lives of several hours and up to several years have been predicted for the longest-lived isotopes of these elements. Thus, the sensitivity of radiochemical separation techniques may present a viable alternative to physical separator systems for the discovery of some of the predicted longer-lived heavy and superheavy nuclides. The advantages of chemical separator systems in comparison to kinematic separators lie in the possibility of using thick targets, high beam intensities spread over larger target areas and in providing access to nuclides emitted under large angles and low velocities. Thus, chemical separator systems are ideally suited to study also transfer and (HI, αxn) reaction products. In the following, a study of (HI, αxn) reactions will be presented and prospects to chemically identify heavy and superheavy elements discussed

[en] The decomposition behavior of group 6 metal hexacarbonyl complexes (M(CO)_6) in a tubular flow reactor is simulated. A microscopic Monte-Carlo based model is presented for assessing the first bond dissociation enthalpy of M(CO)_6 complexes. The suggested approach superimposes a microscopic model of gas adsorption chromatography with a first-order heterogeneous decomposition model. The experimental data on the decomposition of Mo(CO)_6 and W(CO)_6 are successfully simulated by introducing available thermodynamic data. Thermodynamic data predicted by relativistic density functional theory is used in our model to deduce the most probable experimental behavior of the corresponding Sg carbonyl complex. Thus, the design of a chemical experiment with Sg(CO)_6 is suggested, which is sensitive to benchmark our theoretical understanding of the bond stability in carbonyl compounds of the heaviest elements.

[en] The Fast On-line Reaction Apparatus (FORA) was used to investigate the influence of various reaction parameters onto the formation and transport of metal carbonyl complexes (MCCs) under single-atom chemistry conditions. FORA is based on a ${}^{252}$Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes. Those are recoiling from the spontaneous fission source into a reaction chamber flushed with a gas-mixture containing CO. Upon contact with CO, fission products form volatile MCCs which are further transported by the gas stream to the detection setup, consisting of a charcoal trap mounted in front of a HPGe γ-detector. Depending on the reaction conditions, MCCs are formed and transported with different efficiencies. Using this setup, the impact of varying physical parameters like gas flow, gas pressure, kinetic energy of fission products upon entering the reaction chamber and temperature of the reaction chamber on the formation and transport yields of MCCs was investigated. Using a setup similar to FORA called Miss Piggy, various gas mixtures of CO with a selection of noble gases, as well as N${}_2$ and H${}_2$, were investigated with respect to their effect onto MCC formation and transport. Based on this measurements, optimized reaction conditions to maximize the synthesis and transport of MCCs are suggested. Explanations for the observed results supported by simulations are suggested as well.

[en] During previous radioanalytical studies at Paul Scherrer Institute ca. 30 L of acidic waste containing spent nuclear fuel was produced, and now they need to be disposed A flow sheet for conditioning of these waste was designed and the extraction chromatography technique is evaluated. Suitable sorbents, such as AMP_PAN, TBP impregnated resin and DGA resin, were selected for the task of Cs-removal, extraction of U and Pu, and extraction of minor actinides and lanthanides, respectively. A pilot device will be built for preliminary tests with simulated solutions, and the facility will be built and evaluated with the real spent fuel solutions.

[en] A new setup named Fast On-line Reaction Apparatus (FORA) is presented which allows for the efficient investigation and optimization of metal carbonyl complex (MCC) formation reactions under various reaction conditions. The setup contains a ${}^{252}$Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes at a rate of a few atoms per second by its 3% spontaneous fission decay branch. Those atoms are transformed within FORA in-situ into volatile metal carbonyl complexes (MCCs) by using CO-containing carrier gases. Here, the design, operation and performance of FORA is discussed, revealing it as a suitable setup for performing single-atom chemistry studies. The influence of various gas-additives, such as CO${}_2$, CH${}_4$, H${}_2$, Ar, O${}_2$, H${}_2$O and ambient air, on the formation and transport of MCCs was investigated. O${}_2$, H${}_2$O and air were found to harm the formation and transport of MCCs in FORA, with H${}_2$O being the most severe. An exception is Tc, for which about 130 ppmv of H${}_2$O caused an increased production and transport of volatile compounds. The other gas-additives were not influencing the formation and transport efficiency of MCCs. Using an older setup called Miss Piggy based on a similar working principle as FORA, it was additionally investigated if gas-additives are mostly affecting the formation or only the transport stability of MCCs. It was found that mostly formation is impacted, as MCCs appear to be much less sensitive to reacting with gasadditives in comparison to the bare Mo, Tc, Ru and Rh atoms.

[en] Using the Fast On-line Reaction Apparatus (FORA), the influence of various gas-purification columns onto the formation of metal carbonyl complexes (MCCs) under single-atom chemistry conditions was investigated. MCCs were synthesized from single atoms of Mo, Tc, Ru and Rh being produced by the spontaneous fission of ${}^{252}$Cf and recoiling into a CO-gas containing carrier gas atmosphere. The in-situ synthesized MCCs were volatile enough to be transported by the carrier gas to a charcoal trap where they were adsorbed and their subsequent decay was registered by γ-spectrometry. It was found that the type and combination of purification columns used to clean the applied CO-gas strongly influences the obtained formation and transport yields for all MCCs. With the exception of Rh-carbonyl, intense gas-purification strategies resulted in reduced formation and transport yields for MCCs in comparison with less efficient or even completely missing purification setups. It was postulated that the observed reduction in yield might depend on the content of Fe(CO)${}_5$ and Ni(CO)${}_4$, as well as potentially other MCCs, in the CO-gas, being formed by the interaction between CO and the steel-surfaces of FORA as well as from impurities in the used charcoal traps. Subsequently, it was shown that macro amounts of Fe(CO)${}_5$, Ni(CO)${}_4$, Mo(CO)${}_6$ and Re${}_2$(CO)${}_{10}$ added to the used process gas indeed increase significantly the overall yields for MCCs produced by ${}^{252}$Cf fission products. Ni(CO)${}_4$ appeared the most potent to increase the yield. Therefore, it was used in more detailed investigations. Using isothermal chromatography, it was shown that Ni(CO)${}_4$ does not affect the speciation of carbonyl species produced by the ${}^{252}$Cf fission product ${}^{104}$Mo. For ${}^{107}$Tc, ${}^{110}$Ru and ${}^{111}$Rh a speciation change cannot be excluded. For ${}^{111}$Rh a speciation change cannot be excluded. An inter-carbonyl transfer mechanism is suggested boosting the formation of MCCs. The current discovery might allow for new opportunities in various research fields, which are currently restricted by the low overall yields for MCCs produced under single-atom chemistry conditions. Examples are the chemical investigation of transactinides or the generation of radioactive ion beams from refractory metals at accelerators.

[en] Although somewhat in the shadow of the discoveries of new elements, experimental chemical investigations of the heaviest elements have made tremendous progress in the last decades. Indeed, it was possible to experimentally determine thermochemical properties of heavy transactinide elements such as copernicium or flerovium. But will it be possible to chemically study all currently known elements of the periodic table up to element 118? While it is experimentally feasible to work with single atoms, the short half-lives of even the longest currently known isotopes of elements 115 through 118 call for new experimental approaches.

No abstract available