Transmutation of transuranic elements is of interest to lower storage unit cost and long-term radiotoxicity. To make use of existing infrastructure, the deployment of Boiling Water Reactors (BWRs) with hafnium cladding and Mixed Oxide (MOX) fuel was proposed, resulting in a hardening of the neutron spectrum. This work tests varying spatial fuel configurations for maximal burn-up, using Serpent, and study their behaviour in common accident scenarios, simulated by a coupled TRACE/PARCS software suite. To this end, we provide a software solution, which serves to transfer Serpent output of a user defined system in a cross section parameter file, readable by TRACE/PARCS. The results of the transfer were tested for safety performance and, if they provided satisfactory steady states, subjected to a turbine-trip event without bypass, with or without control rod SCRAM. Building on the works by Suvdantstseg [12] and Wallenius & Westlen [7], we chose a Transuranium (TRU) content of 16.48% and a Hafnium-content of 5% with various Higher Actinides (HA) contents and z-axis distributions, intended to either maximize safety performance or minimize void worth and study the results. The chosen fuel loading allows a safe shut-down for both accident scenarios. Sharply rising pressure inside the reactor vessel causes a void collapse. The TRU-content lowers the positive reactivity contribution of increased moderator density, compared to the Uranium Oxide (UOX) baseline. Nonetheless, using a Hf-content of 5% in the cladding and MOX-fuel with 16.48 TRU and 2.06 HA, the void coefficient stays negative during a transitional period of the shutdown, lasting for approximately 200 seconds, before before changing it’s sign.

The objective of this thesis is to study and understand the behavior of the reactivity coefficients (RCs) in a boiling water reactor (BWR) partially within 25 different segments with different void fractions, with enriched oxide fuel (UOX) core, as well as to evaluate the methodologies exposed in [10]. These two normalization  methods (described in chapter 3) are used to analyse the contribution of each segment of the core having different regions (fuel, clad, coolant, moderator and channel box) to the RCs. All the calculations in this work are performed using PSG2 / Serpent – a Continuous-energy Monte Carlo Reactor Physics Burnup Calculation Code. The overall reactivity coefficient's values are exactly the same for both methodologies, but the partial reactivity coefficients are totally differing from each other. Using the symmetric normalization methodology introduced in chapter 3 section 3.4.3 the partial reactivity coefficients become almost the same for both methodologies. Moreover, the overall reactivity coefficients are exactly the same as well. Methodologies for reducing the radiotoxicity of the actinides and fission products produced in nuclear fuels are presently under investigation. Therefore, currently the nuclear reactors are designed not only for power generation, but also are used as transmuters as well, by inserting, for example, the minor actinide to a reactor core the safety parameters can get worse. Moreover, it is wiser to study the partial reactivity coefficients of a reactor core.

This diploma thesis is a follow up work of a previous paper by Johan Strömqvist et. al. [1] In their article they presented a novel method on how to determine the Z-ring radius and the contraction in dividing Escherichia coli. This was done by fluorescent recovery after photobleaching (FRAP) measurements in the cytosol of E.coli cells transfected to express the Enhanced Green Fluorescent Protein (EGFP). The E.coli cell was irreversibly bleached on one side of an already visible invagination in the midcell, and then the fluorescence recovery was followed in time. Since the fluorescence recovery depends on the cross sectional area of the septum that information could be used to derive a mathematical expression to estimate the septal radius of the cell. In this thesis the goal was to, along with cytosolic recovery, examine the recovery after a bleaching pulse in the fluorescent labeled cell membrane. Furthermore it also set out to investigate how the cytosolic fluorescence recovery of EGFP was or could be correlated to the fluorescence recovery of dyes in the cell membranes of the E.coli.

Nuclear waste management represents the main problem related to nuclear power generation. The Swedish project for an ultimate nuclear waste repos- itory  is in a very advanced state and cast iron-copper canisters have been designed with the aim of isolating the spent fuel from the environment for at least 105 years.  Neutrons and gamma radiation emitted by the fuel may induce unexpected embrittlement  and impair the container integrity through formation of point  defect clusters and consequent  copper precip- itation.   Gamma radiation induces displacements by interacting with  the container’s metal lattice and creating high energy electrons. To study this container embrittlement, irradiation experiments that make use of high en- ergy electron beams are required. In order to reproduce the experimental arrangement, a Monte Carlo code named ElectronDamage was developed. The code computes the damage rate induced by a collimated high-energy electron beam on one-dimensional metallic samples and also provides for the damage distribution  as function of depth. The particle energy loss along its trajectory is computed by means of the Bethe-Bloch formula. The scattering cross section and the stopping power are assumed to be constant along the free path.  Collisions against the lattice nuclei are modelled by randomly generating the scattering angle, according to the differential scattering  cross section. A cutoff angle has to be chosen in order to make the cross section function limited and allow for the construction of a PDF. At every collision the exchanged energy is computed. A sharp displacement energy threshold is assumed and the Kinchin-Pease formula is used for the secondary displacement computation.  The energy threshold to produce displacements by electrons is 630 keV in iron. Test simulations were performed in order to validate the code.  Sim- ulated electron ranges  and backscattering coefficients  were computed for several electron energies and compared with theoretical predictions or semi- experimental values. The comparison  was successful, although it showed that  the code is not suitable for beams below 500 keV. Subsequently,   a few relevant energies were selected with the aim of reproducing the gamma spectrum emitted by real spent fuel samples. The total damage rates were computed (in  displacements/electron  unit)  and converted into  dpa/year; considerable contributions are given by gamma fluxes whose energy is lower than 2 MeV. The damage rates provided by the literature were satisfactorily close to the computed ones. Displacement distributions presented a peak, which is located near the irradiated surface and moves inwards as the elec- tron energy increases. Finally, a parametric study of the cutoff value showed that its choice does not induce any effect on the total damage rate, whereas it causes a shrinkage of the distribution toward the irradiated surface and a slight increase of the peak value.

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The Magneto-Optical Kerr Eect (MOKE) is a powerful tool for studying the magnetic properties of various materials such as thin lm multilayers or magnetic nanostructures. This paper presents the construction of two systems for dierent MOKE measurements. The MOKE spectrometer is capable of measuring the magneto-optical Kerr rotation as function of photon energy between 1.55 eV to 3.1 eV (400 nm to 800 nm). Permalloy, Ni, Co and Ni antidot samples have been measured to calibrate the system. A large magneto-optical enhancement is observed for the antidot lm in the expected energy range. The time-resolved MOKE (tr-MOKE) measurements are performed by exciting the samples with magnetic eld pulses. The change in magnetization as a function of time is measured using continuous-wave light. When ready the system will be able to measure the magnetization in the time domain at a sub-nano second scale.

A MOKE setup was constructed and measurements have been performed in order to verify the versatility of this equipment. The quadrupole air core coils are capable of delivering a maximum magnetic eld of 13 mT in longitudinal, transversal as well as polar MOKE. The diractometer enables re　ective scans (Kerr eect) from 20 to 90 degrees and transmissive scans (Faraday eect) from 0 to 90 degrees (optical convention). The combined equipment that constitutes of these two parts enables thorough characterization of optical, magnetical and magneto-optical phenomena which will be of great benet for studies of patterned nano-magnets. The setup is designed to reveal the in　uence of optical eects coupled to various structures like plasmon resonance and plasmonic band gaps into the magnetic and magneto-optical properties of patterned nanostructures.

This bachelor thesis presents an analytical approach to obtain neutron flux distribution function of a critical nuclear reactor in the multigroup approximation. We start with an overview of some basic reactor concepts and tackle the problem with a simple geometry of an infinite slab reactor, where we assume all neutrons to be monoenergetic. Thereafter, we successively treat a few more realistic cases, introducing a more complex geometry as well as several zones of a reactor. Gradually we arrive at two-group approximation evaluations of neutron flux distribution functions in a spherical reflected reactor. / Detta kandidatarbete presenterar en analytisk ansats för att härleda neutronfördelnings-funktioner i en kritisk reaktor med multigrupp approximationer. Vi börjar med en översikt av några viktiga grundkoncept för kärnreaktorer och angriper problemet för en enkel geometri bestående av en oändlig reaktorskiva. Därefter behandlar vi stegvis några mer realistiska fall med komplexare geometrier och flera zoner i reaktorn. Gradvis kommer vi till en två-grupp approximation av neutronfördelningsfunktioner i fallet för en reflektorkläd reaktor.

Within the course of this master thesis project, subcooled nucleate boiling in a vertical pipe has been modeled using CFD. The modeling has been carried out within the OpenFOAM framework and a two-phase Eulerian approach has been chosen. The code can be used to predict the distribution of the local ow parameters, i.e.the void fraction, the bubble diameter, the velocity of both liquid and gas, the turbulent intensity as well as the liquid temperature. Special attention has been devoted to the phenomena which govern the void fraction distribution in the radial direction. Two di erent solvers have been implemented and the simulations have been performed in two dimensions. Firstly, isothermal turbulent bubbly ow is mechanistically modeled in a solver named myTwoPhaseEulerFoa-mAdiabatic. The conservation equations of mass and momentum are solved for the two phases, taking special care in the modeling of the interfacial forces. The turbulence phenomena are described by a classical k- model in combination with standard wall functions for the near-wall treatment. Furthermore, an interfacial area concentration equation is solved and two di erent models for its sink- and source terms (corresponding to bubble coalesence and bubble breakup) have been investigated. Secondly, a solver named myTwoPhaseEulerFoamBoiling has been developed based on the rst solver in order to model a heated wall leading to subcooled nucleate boiling and subsequent condensation in the subcooled liquid. Additional terms accounting for the phase change have been included in the mass and momentum conservation equations as well as in the interfacial area equation. Assuming the gas phase being at saturation conditions, only one energy equation for the liquid phase needs to be solved. The adiabatic solver has been validated against the DEDALE experiment and the simulation results showed satisfactory agreement with the measured data. The predictions obtained from myTwoPhaseEulerFoam-Boiling have been compared to the DEBORA experimental data base. They are qualitatively similar but rather high quantitative discrepancies exist. Grid dependence tests revealed that the latter solver depends on the near-wall grid resolution, a yet unresolved issue related to the application of the wall heat ux as the boundary condition. However, the results were shown to be insensitive to small variations in the applied inlet conditions.

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