Nuclear Energy and Safety Research Division

This work aimed to produce intermetallic samples of platinoid metals (active metal matrix) and lanthanides (co-metal) and via the method of Coupled Reduction, i.e. a thermal treatment of the combination of the lanthanide oxide and noble metal at high temperature, as high as 1100 °C, under a constant flow of H₂. We have demonstrated by means of several techniques, such as Scanning Electron Microscope, Energy Dispersive X-Ray Spectroscopy, Alpha Spectrometry and Radiographic Imaging, that this method, at defined experimental conditions (temperature, pressure and concentration) yields a metallic lanthanide thin film when using platinum as active metal matrix. Conversely, the formation of a bulk intermetallic compound was obtained when using Pd as matrix. Those systems will have applications in different nuclear physic and radiochemistry studies, such as irradiation targets for production of superheavy elements and for nuclear data determination.

An international group of researchers led by the Paul Scherrer Institute has carried out in-depth analyses of the climate impact of blue hydrogen. This is produced from natural gas, with the CO₂ resulting from the process captured and permanently stored. The study concludes that blue hydrogen can play a positive role in the energy transition – under certain conditions.

This highlight presents a successful, in-house developed integration of an Electron Beam Ion Source (EBIS) able to ionize gases to high charge states with a customized commercial MC-ICP-MS. The successful joining of the two ion flight paths is a milestone towards comprehensive routine analyses of solids, liquids, and gases using THE SAME MASS SPECTROMETER, the latter analyses free from atmospheric contamination. After implementation of an introduction system for gas mass spectrometry, routine analyses will comprise isotope ratio and relative abundance determinations of fission gases in used nuclear fuel. In addition to the unique versatility of the MC-EBIS-ICP-MS, inclusion of the EBIS furthers opens the little-studied field of mass spectrometry of highly charged ions.

Water boiling control evolution of natural geothermal systems is widely exploited in industrial processes due to the unique non-linear thermophysical behavior. Even though the properties of water both in the liquid and gas state have been extensively studied experimentally and by numerical simulations, there is still a fundamental knowledge gap in understanding the mechanism of the heterogeneous nucleate boiling controlling evaporation and condensation. In this study, the molecular mechanism of bubble nucleation at the hydrophilic and hydrophobic solid–water interface was determined by performing unbiased molecular dynamics simulations using the transition path sampling scheme. Analyzing the liquid to vapor transition path, the initiation of small void cavities (vapor bubbles nuclei) and their subsequent merging mechanism, leading to successively growing vacuum domains (vapor phase), has been elucidated. The simulations reveal the impact of the surface functionality on the adsorbed thin water molecules film structuring and the location of high probability nucleation sites.

After several years of loyal and reliable services during heavy duty operation in a reactor, nuclear fuel must be discharged and go into retirement. For Switzerland, the final place of retirement is planned to consist of a deep geological repository where the used nuclear fuel will be disposed. Before the repository is constructed, the used fuel will need to be stored in wet pools and/or dry storage casks.

During all this time, safe handling of the fuel will remain the top priority for operators and regulators. To gain better knowledge on the relevant phenomena which could potentially affect the fuel thermo-mechanics and safety characteristics during long storage periods as well as to allow predicting their evolution, simulation models are being developed at PSI within the DRYstars project.

A first milestone was recently achieved with the development of models coupled to state-of-the-art fuel performance codes for each of the three main categories of phenomena considered as having high safety relevance for storage, namely helium behaviour, creep behaviour and hydrogen behaviour.

Sustainable, synthetic fuels, so-called e-fuels, can help reduce CO₂ emissions. For their production, electricity from renewable sources is required in order to allow for a close to CO₂-neutral balance. The availability of electricity from renewable sources, which ensures the climate benefits of e-fuels, is currently still limited. “Especially in order to produce on a larger scale, a lot of renewable electricity is needed,” explains Christian Bauer, researcher at the Laboratory for Energy Systems Analysis (LEA) at PSI.