Volume 107, Issue 7 - Special Issue: Herrmann Memorial Issue / Guest Editors: Frank Rösch und Norbert Trautmann

The TRIGA Mark II-reactor at the Johannes Gutenberg University Mainz (JGU) is one of three research reactors in Germany. The TRIGA Mainz became first critical on August 3 rd , 1965. It can be operated in the steady state mode with a maximum power of 100 kW th and in the pulse mode with a peak power of 250 MW th and a pulse length of 30 ms. The TRIGA Mainz is equipped with a central thimble, a rotary specimen rack, three pneumatic transfer systems, four beam tubes, and a graphite thermal column. The TRIGA Mainz is intensively used both for basic and applied research in nuclear chemistry and nuclear physics. Two sources for ultra-cold neutrons (UCN) are operational at two beam ports. At a third beam port a Penning-Trap for highly precise mass measurements of exotic nuclides is installed. Education and training is another main field of activity. Here, various courses in nuclear and radiochemistry, reactor operation and reactor physics are held for scientists, advanced students, engineers, and technicians utilizing the TRIGA Mainz reactor.

The Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is a powerful, highly reliable and selective reaction which allows for a rapid synthesis in high yields and under mild conditions (pH, temperature). However, the cytotoxicity of copper requires its complete removal prior to an application in vivo . This is an issue especially when it comes to CuAAC reactions on macromolecular structures or drug delivery systems, as copper might be retained by these systems. Thus, a quantification of the final copper content of these systems is inevitable, which we exemplified for a CuAAC reaction on liposomes using 64 Cu-spiked Cu(I). In this respect, a Cu(II) nitrate solution was irradiated at the TRIGA Mark II research reactor Mainz to obtain c.a. [ 64 Cu]Cu(II). The irradiated solution was directly used for a CuAAC on liposomes. After purification, their copper content was calculated utilizing γ-ray spectrometry. Only 0.018% of the added 64 Cu-activity was still present in the liposome containing fractions after purification. This refers to a total amount of copper of 0.17 ng. The amount of retained copper is so low, that an in vivo application of the liposomes is absolutely reasonable. Besides this particular study, the experimental methodology may be applied to study many other CuAAC reactions, used for the synthesis of radiolabeled or non-radioactive species, which are intended for human applications.

Fission products recoiling from a 252 Cf spontaneous fission source were stopped in various mixtures of inert gases containing CO and NO. For the elements of the transisition metal series Mo, Tc, Ru, and Rh previous observations of pure carbonyl complexes were reproduced. However, no formation of volatile mixed nitrosyl-carbonyl complexes or pure nitrosyl complexes for these elements have been observed. Instead, efficient production of volatile nitrosyl compounds for single iodine atoms, presumably nitrosyl iodide, NOI, was detected. This observation is of interest as potential transport path for iodine in nuclear accident scenarios and as a model for radiochemistry with the recently discovered heaviest halogen tennessine (Z=117).

The development of automated rapid chemistry techniques and their application for batch-wise, chromatographic separations of heavy elements in the liquid-phase are outlined. Starting in the mid-1970s with manually performed separations using pressurized liquid-chromatography techniques, this development led to the first version of the Automated Rapid Chemistry Apparatus, ARCA, in the early 1980s. After a breakthrough to a much higher level of automation and miniaturization, the new apparatus ARCA II was built in the late 1980s. Based on it, the Automated Ion-exchange separation apparatus coupled with the Detection system for Alpha spectroscopy, AIDA, became operational in the late 1990s. In the context of technical and technological advancements, this article discusses the successful application of these instruments for (i) the search for superheavy elements, (ii) cross section measurements of actinide elements produced in multi-nucleon transfer reactions with actinide targets, (iii) chemical separation and characterization of the heavy actinides mendelevium, Md, and lawrencium, Lr, and (iv) studies of the transactinide elements rutherfordium, Rf, dubnium, Db, and seaborgium, Sg. Details of the separations are outlined together with the big advancements made over time and the limitations reached. For the transactinide elements, examples are given for their observed chemical behavior; often affected by an interplay between hydrolysis and complex formation. Influenced by relativistic effects, chemical properties of these elements sometimes deviated from those of their lighter homologs in the Periodic Table.

Some highlight examples on the study of production and chemical properties of heaviest elements carried out mostly at GSI Darmstadt are presented. They focus on the production of some of the heaviest known elements ( 114 Fl, 115 Mc, and 117 Mc), studies of non-fusion reactions, and on chemical studies of 114 Fl. This is the heaviest element, for which chemical studies have been performed to date.

The precise determination of atomic and nuclear properties such as masses, differential charge radii, nuclear spins and electromagnetic moments of exotic nuclides has recently been extended to the region of the heaviest elements. To this end, ion trap-based techniques and laser spectroscopy methods have been employed to provide information complementary to that obtained by nuclear spectroscopy. This enables more detailed studies of the atomic and nuclear structure of these exotic nuclides far from stability. This contribution summarizes some of the recent achievements and addresses future perspectives for measurements on even heavier elements.

Results from batch type experiments were modeled using the 2 SPNE SC/CE model developed by Bradbury and Baeyens. This work focused on the applicability of this model to the sorption of Np(V) on Na-montmorillonite under high saline conditions (0.1–3.0 M NaCl) in the pH range of 2–10 and in the presence of dissolved CO 2 ( p (CO 2 ) = 10 −3.3 atm). Under ambient air conditions two additional surface complexation species had to be taken into account, which are ternary species involving one carbonate ligand (≡SONpO 2 (CO 3 ) 2− , ≡SONpO 2 (CO 3 )Na − ). The gained set of complexation parameters was successfully tested over a wide range of Np(V) concentrations (10 −4 to 10 −12 M) under Ar atmosphere and ambient air condition.

Natural clay rocks like Opalinus (OPA) and Callovo-Oxfordian (COx) clay rock are considered as potential host rocks for deep geological disposal of nuclear waste. However, small organic molecules such as propionate and lactate exist in clay rock pore water and might enhance Np mobility through a complexation process. Therefore, reliable complex formation data are required in the frame of the Safety Case for a nuclear waste repository. A solvent extraction technique was applied for the determination of NpO2+${\rm{NpO}}_2^ + $ complexation with propionate and lactate. Extraction was conducted from isoamyl alcohol solution containing 10 −3 M TTA and 5 · 10 −4 M 1,10-phenanthroline. Experiments were performed in 0.5–2.6 m NaCl solutions at temperatures ranging from 22 to 60 °C. Formation of 1:1 Np(V) complexes for propionate and lactate was found under the studied conditions. The SIT approach was applied to calculate equilibrium constants β °(T) at zero ionic strength from the experimental data. Log β °(T) is found linearly correlated to 1/ T for propionate and lactate, evidencing that heat capacity change is near 0. Molal reaction enthalpy and entropy (ΔrHm∘${\Delta _{\rm{r}}}H_{\rm{m}}^ \circ $ and ΔrSm∘${\Delta _{\rm{r}}}S_{\rm{m}}^ \circ $) could therefore be derived from the integrated van’t Hoff equation. Data for log β ° (298.15 K) are in agreement with literature values for propionate and lactate. Np(V) speciation was calculated for concentrations of acetate, propionate and lactate measured in clay pore waters of COx. In addition, the two site protolysis non-electrostatic surface complexation and cation exchange (2SPNE SC/CE) model was applied to quantitatively describe the influence of Np(V) complexation on its uptake on Na-illite, a relevant clay mineral of OPA and COx.

Nuclear forensic analysis of uranium oxide fuel pellets and the respective data interpretation have proven to be important elements of the investigative process when such material is found out of regulatory control. Uranium oxide fuel pellets are produced at industrial scale and have to meet tight technical specifications. Variations in the production process of different manufacturers or fuel fabrication facilities offer an additional source of information. The compilation of such information in a nuclear materials database has proven to be a highly valuable resource. In consequence, measureable material properties (referred to as “signatures”) such as the isotopic composition, the physical dimensions, the chemical impurities, the products of the radioactive decay of uranium and the microstructure allow establishing the processing history of the material. To this end, dedicated analytical methods have to be developed and suitable methods for data evaluation and interpretation need to be utilised. The successful application of these nuclear forensic tools is illustrated with two case studies on real incidents of illicit nuclear trafficking of uranium oxide fuel pellets.

Resonance ionization mass spectrometry is an efficient tool to detect minute amounts of long-lived radio-isotopes in environmental samples. Applying resonant excitation and ionization with pulsed laser radiation within a hot cavity atomizer enables the sensitive detection and precise quantification of long-lived actinide isotopes. Due to the inherently element selective ionization process, this method ensures ultimate suppression of contaminations from other elements and molecules. The characterization of in-source resonance ionization of the actinide elements U, Th, Np, and Am using a compact quadrupole mass spectrometer (QMS) setup are discussed.

The development of a highly efficient resonance ionization scheme for lutetium is presented. A laser ion source, based on the all-solid-state Titanium:sapphire laser system, was used at the 30 keV RISIKO off-line mass separator to characterize different possible optical excitation schemes in respect to their ionization efficiency. The developed laser resonance ionization scheme can be directly applied to the use at radioactive ion beam facilities, e. g. at the CERN-MEDICIS facility, for large-scale production of medical radioisotopes.