Scientific Highlights NES

Datum
28. Oktober 2022
ETSON Highlight Teaser

ETSON Workshop at PSI Towards Artificial Intelligence Informed Nuclear Safety Assessments

Data science (DS) and artificial intelligence (AI) methods opens up an immense range of new opportunities and challenges in the context of continuously enhancing the complex methodologies used as basis for nuclear safety assessments. To this aim, following discussions in the ETSON Technical Board on Reactor Safety, the PSI laboratory for reactor physics and thermal-hydraulics organized on October 20-21, 2022, an international workshop to review and discuss DS/AI within ETSON, the network of European research and expert organizations providing scientific support to national nuclear authorities. With close to 40 participants, the workshop, organized as a hybrid meeting, allowed to put in evidence that similarly as at PSI, a wide and growing range of developments with integration of DS/AI methods are currently taking place in order to complement and/or inform nuclear safety analysis methodologies.  

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27. Oktober 2022
5232

“More objectivity would be helpful”

Energy and Climate

The current energy debate could do with more facts and less gut feeling – argue Thomas J. Schmidt, renewables expert, and Andreas Pautz, nuclear energy specialist.

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25. Oktober 2022
ECMFL NURETH Highlight Start GIF

Award winning work on high-resolution X-ray radiography methods for boiling experiments at high pressure.

Light Water Reactors (LWRs) such as the ones operating in Switzerland work at relatively high temperatures and pressures. As a consequence, thermal-hydraulics experiments investigating relevant LWRs phenomena at prototypical conditions require test sections with relatively thick steel walls. This poses significant challenges for the implementation of suitable instrumentation to capture phenomena of interest, such as the flow regimes during transition from liquid to steam. The characterization of flow regimes in the presence of boiling is rather complex, and their better understanding would allow to develop mathematical modeling tools that can be used to optimize equipment and better assess safety margins. To perform in-situ measurements of the boiling process under high-pressure conditions, the team of authors from PSI, ETH, and the University of Michigan has developed a new high-fidelity and high-speed imaging system based on x-ray radiography, which provides high-resolution details on the boiling process while being non-intrusive. Since the instrumentation is located outside of the test section, it has also the advantage that can be easily moved to take measurements in different region of the test sections. 

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7. September 2022
LES

CASH+ solid solution cement model

A new incrementally extendable thermodynamic model, CASH+, was developed, aimed at accurately describing equilibrium composition, solubility, and elemental uptake of C-A-S-H gel-like phases at varying chemical conditions in cement systems. Cement is widely used as matrix and backfill for low and intermediate level waste. Calcium-Aluminum-Silicate Hydrates (C-A-S-H) are the most important binding phases in cement. They are also responsible for the initial entrapment of radionuclides via sorption or solid solution formation mechanisms. Therefore, the thermodynamic modelling of C-A-S-H stability, solubility and interaction with radionuclides in cement porewater is crucial for understanding hydration, blending, degradation of cement-based materials and for the performance assessment of cementitious repositories.

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17. Juni 2022
Figure 3

Synthesis of Metallic Lanthanide Thin Samples

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.

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22. April 2022
Fig.1

Blue hydrogen can help protect the climate

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.

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12. April 2022
First combined Plasma and Gas Source Mass Spectrometer for alternate isotope and element ratio Analyses of Solids, Liquids, and Gases

MC-EBIS-ICP-MS – a unique dual Ion Source Mass Spectrometer

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.

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7. April 2022
Water vapor nucleation at ZnO2 interface

Deciphering the molecular mechanism of water boiling at heterogeneous interfaces

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.

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24. Januar 2022
retired nuclear Fuel Teaser

Taking good and safe care of the retired … nuclear fuel

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.

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