The Swedish concept for storage of highly radioactive spent nuclear fuel is called the KBS-3 program. The proposed procedure is that the waste will be stored in a deep repository, 500 meters down in the Swedish bedrock, for 100 000 years. The fuel will be sealed inside cast iron cylinders surrounded by copper. The iron-copper canisters will then be placed one by one in holes and embedded in bentonite clay. The environment in the deep repository will be that of an underground rock cave, there will be groundwater and low amounts of oxygen present. Substances which are likely to react with the copper canister and cause corrosion are oxygen, sulphides and reactive water radiolysis products. Gamma radiation from the spent nuclear fuel will penetrate through the canister and further into the bentonite clay. When the gamma radiation comes in contact with the water in the bentonite clay, water radiolysis will occur. Corrosive radiolysis products are for example hydroxyl radicals, solvated electrons and hydrogen peroxide. The main purpose of this work was to study the effect of gamma radiation on copper pieces, in an aqueous environment, both under oxic and anoxic conditions. The surfaces of the copper pieces were characterized using scanning electron microscopy (SEM) and infrared absorption spectroscopy (IRAS). The dissolution of copper was measured using inductively coupled plasma spectroscopy (ICP). A second study was also performed where the reactions of three different oxidants; hydrogen peroxide, permanganate and iridium hexachloride, were studied in the presence of copper in an inert environment. All of the reactions were studied spectrophotometrically and the dissolution of copper was measured using inductively coupled plasma spectroscopy (ICP). The SEM measurements showed corrosion products on the irradiated copper pieces both under oxic and anoxic conditions. Under anoxic conditions the corrosion products had a center of a small cavity which was surrounded by a larger, flat, circular area. From that area, wider cavities were spreading out in apparently random directions. SEM-EDS measurements detected oxygen on the surface of the corrosion products. ICP measurements of the water phase showed that the water from irradiated samples contained higher levels of copper than unirradiated samples. ICP measurements from the reactions of copper in the presence of oxidants showed that copper was only dissolved in the presence of iridium hexachloride. These results show that gamma radiation causes corrosion of copper in an aqueous environment, both under oxic and anoxic conditions. It can also be concluded that hydrogen peroxide is not the radiolysis product that causes the dissolution of copper when copper is irradiated in an aqueous and inert environment.

The European XFEL is an X-ray free electron laser research facility that generates ultrashort, high intensity flashes. Three SASE undulator systems are made of undulator segments and intersection components. Permanent magnets that form the segments, may potentially suffer demagnetization due to the stray radiation that comes from the interaction between electrons and the beam pipe. A gamma spectrometer (GR1-A, developed by Kromek) is planned to be placed at the entrance of one of the undulator segments of SASE1. Monte Carlo simulations, using Geant4, have been performed to study gamma radiation flux at possible measurement areas. The results show that in some cells the expected flux is larger than the maximum throughput, while for two segments there are areas which satisfy the limitations of the detector. An improvement of the geometry of the Geant4 code has also been done to make simulations more in line with the real systems. A comparison between dose results from the new and the former code shows that components placed at the intersections have a significant impact on dose distributions, especially quadrupole magnets.

To safely encase and store spent fuel assemblies in its final geological storage, accurate measurements of their heat output must be performed. To this end, information about the geometry and sensor set-up of the calorimeter at the interim storage facility CLAB was gathered. The data from the temperature sensors where compared to each other and an analytical expression was proposed to fit the data. A methodology for calculating calibration curves was formulated and its uncertainties were evaluated. Differences were found between the fits of measurements from differing measurement campaigns. The measurement campaigns resulted in calibration curves with notable offset from each other. The computer code SERPENT2 was used to construct a 3d geometry model of the calorimeter and the ratio of photons entering and escaping the calorimeter wall was calculated for photon energies which dominate the gamma spectrum from spent fuel assemblies of about 5 to 40 years cooling time.

In recent years there has been a considerable amount of work done on developing chemicals that would inhibit mold growth when applied to fresh fruit, and at the same time, be acceptable to man when taken orally. This would save many thousands of tons of fresh produce that are lost each year by spoilage before it ever reaches the consumer. Along with the development of new chemicals to inhibit mold growth there is a substantial amount of research being done on developing a packaging film that will prevent recontamination of the produce, at the same time allowing the passage of gasses into and out of the package to allow respiration of the fruit. During the present century much emphasis has been placed on growing certain varieties of fruit for our specific needs. It has been found that particular varieties are better for canning and that other varieties are better for freezing. With the release of atomic energy for peaceful use in 1933 by the United States Congress, a new era of food preservation was introduced. Men in the scientific fields believe it is possible to extend the shelf-life of fresh fruits without altering their physical condition to great extent. Many institutions have been awarded grants and contracts to work on various phases of food preservation with atomic energy. Utah State University was awarded a contract by the United States Army Quartermaster Corp to study the use of gamma radiation for extending the shelf-life of fresh produce. It was with this idea in mind that work for this thesis was conducted to study the effects of gamma radiation, fungicides, and packaging film on the microbial growth on certain varieties of strawberries and cherries. In addition, experiments were conducted using fungicides and packaging films in order to lower the dose of radiation necessary to prevent mold growth. In order for this method of preserving fresh fruit to become successful, new and more economical methods and techniques in handling the materials will have to be developed.

Alkaline fuel cells are a promising technology, with their sturdy design and many applications they are held back mostly by their cost. By introducing a catalyst, the activation energy of the cell can be reduced to an overcomable amount. Unfortunately, due to the high cost and sparse availability of the most used catalyst metal today, platinum, it has become apparent that a new suitable catalyst must be found in order to make the fuel cells economically feasible. Silver and palladium have been proposed as promising alternatives, sharing a majority of the traits but with a fraction of the cost. The original aim of this project was to study the performance of electrodes in an alkaline electrolyte loaded with different ratios of palladium and silver. However, due to the COVID-19 situation the project was not able to be completed and the aim of the project changed. The new aim was divided into two parts. The first one being to study how the initial concentration of silver ions affects the size of the obtained particles. This was achieved by a radiolysis-based method of synthesis in an aqueous solution. The second aim was to study the performance of the electrodes loaded with different amounts of silver and different average particle size. However, this part was not possible to conduct either. Therefore, results from a previous study performed by I. L. Soroka et al. was used for discussion. The results point towards a lower initial concentration achieving a smaller average particle size and a lower loading of catalyst on the electrode can be compensated by a smaller average particle size of the catalyst.

L'exposition à des niveaux faibles de radiation ionisante est connue pour déclencher une réponse adaptative qui inclut la stimulation immunitaire et l'augmentation des effets protecteurs à long terme incluant l’amélioration de la détection et la réparation de dégâts causés à l’ADN, la croissance renforcée et la longévité. Tandis que les aspects hormetique de la réponse adaptative augmentent clairement la santé physique en présence de stress environnementaux, ils doivent la diminuer dans des conditions environnementales normales parce que les mécanismes biologiques responsables ne sont pas maintenus dans un état amélioré, mais exigent plutôt une certaine forme d'exposition sensibilisante. Il a été suggéré que la stimulation de la réponse adaptative pourrait être métaboliquement coûteuse cependant aucune mesure directe du coût métabolique de la croissance stimulée de radiation a été précédemment essayée. Cette thèse a évalué si la croissance stimulée de radiation du grand corégone (Coregonus clupeaformis) est accompagnée par un compromis dans l'efficacité métabolique ou par une augmentation durable de demandes énergiques. L'exposition à un régime fractionné de radiation ionisante d'une source de 137Cs s’est avéré stimuler considérablement la croissance dans des embryons du grand corégone comparés aux contrôles avec une augmentation correspondante de la consommation de jaune. Cependant, les mesures d'efficacité métabolique utilisant une série de temps de poids secs non préservés ont montré que la croissance stimulée était non-accompagnée par une réduction de l'efficacité métabolique. Une température moyenne exponentiellement transformée a été utilisée comme un point de référence quantitative pour évaluer la vulnérabilité du développement des embryons du grand corégone à la disparité phénologique. Le temps d’éclosion différait des prédictions de références sous des régimes thermiques asymétriquement variables. Les écarts ont été attribués aux embryons grandissant à dans un stade plus avancée de développement sous des températures basses. Le terme heterograde est proposé pour décrire la dépendance thermique dans l'étape d’éclosion qui peut avoir évolué comme un mécanisme pour synchroniser l’éclosion de larves viables pour l'augmentation de la densité de zooplancton qui accompagne le débâcle printanière Un modèle de prédiction incorporant l’éclosion heterograde a permis une amélioration significative dans l’exactitude des prédictions comparé aux modèles précédents. L'efficacité énergique a une importance particulière pour le grand corégone comme il a une des périodes d'incubation naturelles les plus longues pour un poisson d'eau douce, avec des températures d'incubation les plus basses et avec des œufs seulement 10 % de la taille de la plupart des salmonidés non-coregonine. L'évolution de mécanismes pour synchroniser l’éclosion au démantèlement de couverture de glace hivernale met en évidence la vulnérabilité du grand corégone à la disparité phénologique et ce par le développement accéléré qui cause l’éclosion asynchrone des embryons avec le démantèlement de la couverture de glace d'hiver ou par une augmentation durable de demandes énergiques qui augmentent leur vulnérabilité à la famine. L'absence de compromis mesurable dans l'efficacité métabolique indique ce dernier comme un coût général plausible de hormesis. / Exposure to low levels of ionizing radiation is known to trigger an adaptive response that includes immune stimulation and the up-regulation of long-lasting protective effects including improved detection and repair of DNA damage, enhanced growth, and longevity. While the hormetic aspects of the adaptive response clearly increase fitness in the presence of environmental stresses, they must decrease fitness under normal environmental conditions because the responsible biological mechanisms are not maintained in an upregulated state but rather require some form of sensitizing exposure. It has been suggested that stimulation of the adaptive response could be metabolically costly however no direct measurement of the metabolic cost of radiation stimulated growth has been previously attempted. This thesis assessed whether radiation-stimulated growth in the lake whitefish (Coregonus clupeaformis) is accompanied by a trade-off in metabolic efficiency, or by a sustained increase in energetic demands. Exposure to a fractionated regime of ionizing radiation from a 137Cs source was found to significantly stimulate growth in lake whitefish embryos compared to controls with a corresponding increase in yolk consumption. However, measurements of metabolic efficiency using a time series of unpreserved dry weights showed that the stimulated growth was unaccompanied by a reduction in metabolic efficiency. An exponentially transformed mean temperature was used as a quantitative baseline to assess the vulnerability of developing whitefish embryos to phenological mismatch. Hatch timing was found to deviate from baseline predictions under asymmetrically variable thermal regimes. The deviations were attributed to the embryos growing to a more advanced stage of development at low temperatures. The term heterograde is proposed to describe the thermal dependency of hatching stage which may have evolved as a mechanism to synchronize the hatching of viable larvae to the increase of zooplankton density that accompanies spring break-up. A predictive model incorporating heterograde hatching yielded a significant improvement in predictive accuracy over previous models. Energetic efficiency is of particular importance to the lake whitefish as it has one of the longest natural incubation periods of any freshwater fish, at some of the lowest incubation temperatures, and with eggs only 10% the size of most non-coregonine salmonids. The evolution of mechanisms to synchronize hatching to the break-up of winter ice cover highlights the vulnerability of the lake whitefish to phenological mismatch whether through accelerated development that causes embryos to hatch asynchronously with the break-up of winter ice cover, or through a sustained increase in energetic demands that increases their vulnerability to starvation. The absence of any measurable trade-off in metabolic efficiency points to the latter as a plausible general cost of hormesis. / Dissertation / Doctor of Philosophy (PhD)

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There is a large amount of interest and research currently going into studying the effects of low dose radiation on humans, and bridging the gap with the data from the effects of high dose radiation. Much work is to be done to understand low dose exposures such as from medical treatments and those who work with or around radiation. Two popular and widely known examples of low-dose phenomena are the radiation induced bystander effects and the radioadaptive response (RAR). This research involves the study of the impact of a low dose of radiation that is administered several hours after a high – even fatal – dose is given, which contrasts the traditional RAR where a low priming dose is given before a high dose and can lead to increased cell survival. Many different parameters were checked to see if cell survival can be enhanced or diminished depending on the stage of the cell cycle, cell growth conditions, and cell profiling differences in protein function (namely the TP53 gene). Additionally, the post-conditioning response was contrasted to see if it was possible to see any effects from the newly emerging area of bystander signalling, UV BioPhotons, would be present in cell lines that either did or did not exhibit a post-conditioning effect. It was shown that post-conditioning has a protective effect on survival of the cells in certain dose ranges and certain cell lines. The post-conditioning effect also appears to be stronger in magnitude than the classic RAR. No relationship between gamma-induced biophoton signalling and post-conditioning was observed, nor is it certain whether an acute gamma-field can induce significant UV biophoton damage. This thesis is aimed to explore the various parameters by which post-conditioning effects occur on various Human cancers. / Thesis / Master of Science (MSc) / This research looks at the effects of radiation on cells. More specifically, how do low doses of radiation affect cells after they have already been treated with higher doses of radiation. Moreover, can cells communicate through non-physical methods, such as through invisible light? The research focuses primarily on cancer cells and their responses to varying doses of radiation treatments.

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