This study explores how atmospheric temperature affects the rate of muons detected by KM3NeT’s ORCA and ARCA detectors. By comparing measured rates with simulations, a clear seasonal pattern is found, but unexpected differences suggest issues with the simulations. Adjustments to the data improve results but don’t fully resolve the discrepancies, pointing to areas for further investigation.

The ongoing worldwide energy transition has prompted significant scientific interest in energy storage. Rechargeable lithium-ion batteries have become a standard for energy storage in mobile devices and electric vehicles for their mass-energy density. While industry standard lithium-ion cells are currently based on liquid electrolytes, solid electrolytes promise to bring the next step towards safety, energy density and sustainability. However, there are critical challenges, notably improving the lithium conduction of solid electrolytes. Furthermore, as a relatively new research field it is important to target high recyclability and sustainability for materials early on. Battery modelling facilitates performance comparisons of for example battery materials and geometric properties, and subsequent optimisation. The report treats battery modelling with a specific focus on solid electrolytes. Two solid electrolyte models, based on weak electrolyte theory and a lattice gas model by Landstorfer et al., were implemented in the Multiphase Porous Electrode Theory software (Smith,2017). The former is relevant for glass type electrolytes, while the latter models crystalline materials. The models showed comparable performance, with a constant voltage offset but good mutual agreement in term of behaviour. It is important to verify the results experimentally. The numerical methods used in porous electrode theory were treated with the creation of a standalone porous electrode model, with separate domains for the electrolyte and active cathode particles. This model is stable and functional with the two domains in isolation, while a fault remains in the coupling between the domains. Lastly, a proposal is made for the addition of interface regions in the MPET software. With these domains situated between the bulk electrolyte and active cathode particles, porous electrode models could include a variety of phenomena that are currently impossible to implement. For solid electrolytes in particular, modelling dynamic stress effects and lithium conduction across particle boundaries would be valuable additions.

In this study, non-destructive methods are applied to quantify the influence of concrete degradation by geologic conditions on the ability to retain nuclear waste deep underground in The Netherlands. Nuclear reactors play an important role in all four scenarios of the recent report of the IPCC to reach the CO2 reduction goals. Safety related criticism against nuclear energy technology are less relevant for Generation IV nuclear power plants, of which several are scheduled to be constructed in Europe within the next few years. This is partially due to the inherent safety features of Gen IV power plant designs, where disasters experienced before (e.g., Chernobyl, Fukushima) are technically impossible. Concrete samples provided by COVRA are degraded by immersion in a solution that contains chlorides and sulphates in concentration levels that are similar to geologic conditions. The influence of concrete degradation on the internal structure of concrete has been investigated using X-ray and Neutron radiography. Pore size distributions, pore geometry and sorptivity are presented. In order to validate the results, standardized tests are performed and the results are compared.

The battolyser concept is based on an old fashioned nickel iron battery, consisting of a positive nickel(oxy) hydroxide electrode and negative iron (hydroxide) electrode. Research has been performed on the structural changes of the nickel and iron electrode upon charge and discharge. A lot of research can be found for the nickel electrode, but crystal structure studies are few. Much less research is performed on the iron electrode. Therefore the structural changes of the nickel(oxy) hydroxide and iron (hydroxide) electrodes during operation are further researched. Ni(OH)2 exists in the form of an α- or β-modification and NiOOH in a β- or γ-modification. The structure of the nickel(oxy)hydroxide phases has layers of edge-sharing NiO2 octahedra, where in between guest atoms can situate. Conventional nickel electrodes operate mainly between β-Ni(OH)2 and β-NiOOH, so most research focussed on this area. Upon overcharge the γ-NiOOH is formed and when discharging a direct reduction of β-NiOOH and γ-NiOOH into β-Ni(OH)2 occurs. The research on the nickel electrode published in this thesis is compared with a previous discharge study performed by Morishita et al. In their Rietveld refinement of the β-phases an ideal and fault phase model are assumed and the weight fraction of all phases present in the samples at 0, 50, 100 and 150% of state of charge (SOC) are determined. For the iron electrode four phases can be distinguished. The pure Fe in the electrode upon discharge becomes Fe(OH)2, under deep discharge this transforms even further towards FeOOH. For the deactivation process the reaction moves towards magnetite (Fe3O4). First the battery electrodes from the shelf are analysed by SEM-edx , X-ray diffraction and neutron diffraction. Then neutron powder and X-ray diffraction analysis have been performed to study the structural changes of the electrodes during charge and discharge. The nickel electrodes are measured at various states of charge from 0 to 100% and iron electrodes 0 to 90%. Preliminary experiments for the in-situ neutron diffraction test setup are performed. Different thicknesses of quartz glass, several sizes of nickel foam current collectors are tested for the amount of their background noise. In the nickel electrode are next to the carbon, 3 phases present. In the comparison with Morishita et al. significant differences are found. The transition towards β-NiOOH and subsequently γ-NiOOH occurs faster. Already at 50% of SOC the weight fraction of β-NiOOH is 58 wt% and at 100% of SOC the γ-NiOOH is 57 wt%. The c-parameter of γ-NiOOH is in agreement with Morishita et al. with a lattice distance of 20.8 Å. Morishita et al. did not specify how they determined the state of charge, so maybe they calculated the SOC in a different way. In the iron electrode three phases are identified, namely iron (Fe), goethite (FeOOH) and magnetite (Fe3O4). This is a strange result, because where Fe(OH)2 is expected, FeOOH is found. Probably discharged too far, moving the reaction into the second discharge plateau. The weight fraction of Fe increases and FeOOH decreases with increasing state of charge. The hydrogen content is decreasing with increasing SOC proportional to the background function for both the nickel and iron electrode.

Solid state lithium ion batteries are generally safer than liquid electrolytes. Li6PS5Cl is a promising electrolyte with an instability in the active material and electrolyte interphase which causes an increase in impedance and capacity loss.
Doping with stable salts of LiCl and LiF could affect the stability. It is found that doping LiCl reduces the specific capacity retention despite having higher ionic conductivity from EIS. With the ex-situ XRD analysis, it is found that the decomposition is less than of pristine argyrodite. This could be due to poor interphase contact. In the case of dopant LiF, small doping of the argyrodite decreases the specific capacity retention of the active material which may be due to lowered ionic conductivity. The higher amount of LiF doped argyrodite improves the specific capacity retention despite the lower ionic conductivities. This could be due high decomposition rate. Alternatively, another doping method was used, but it was found to have higher chemical decomposition despite having good specific capacity retention. To improve the quality of this research, better synthesis of the argyrodite is preferred as this research has side phases. Further analysis that could be included are: TEM, XRD in-operando mode, and EDS.