The purpose of this project was to map the current method for decommissioning / disposing of the Nano-wire reactor at Sol Voltaics. Additionally, alternatives should be suggested based on the findings during the mapping processes and the subsequent analysis. The aim of the presented alternatives was to improve the current workflow for reactor decommissioning based on five identified areas; Rules and Regulations; Environmental aspects; Safety aspects; Economical aspects and Logistical aspects. The existing disposal procedure was divided into six steps. The first step involves a purging procedure to make sure no hazardous gases remain in the reactor. The second step is to dismantle and seal the reactor. The third step is to move the reactor to a loading dock. The fourth step is the transport between Active Biotech in Lund and Sydblästring AB in Malmö. The fifth step is the disassembly and cleaning process of the reactor parts, including waste management. The sixth and final step is to move the cleaned parts to SYSAV in Malmö for final disposal. Finally, Rules and Regulations as well as Safety aspects were identified as having partial improvement potential. Ideas for possible alternatives in these areas was devised and analyzed according to all five areas to make sure that the improvements in one area would not bring undesirable shortcomings in another.

Nuclear plant stainless steel can become contaminated by radionuclides during normal operation whereby the final disposition of these materials then becomes a major decommissioning challenge to address. Characterisation of the chemical and metallurgical processes that underpin contamination is essential in consideration of developing cost effective decontamination and prevention methods, as are in situ measurement techniques that allow assessment of contamination. To address these issues, contamination experiments to simulate the nitric acid-based reprocessing streams of the PUREX (Plutonium Uranium Redox Extraction) process, and alkaline spent fuel storage ponds were investigated. Solution and surface spectroscopic measurements were performed to characterise the sorption behaviour of stable analogues of two high yield fission products, Sr-90 and Cs-137, on as received and 30 % cold rolled AISI Type 304 stainless steel, respectively. In addition Laser Induced Breakdown Spectroscopy (LIBS) was also investigated as a standoff contamination assessment technique. Fission product accumulation was modelled to a second order kinetic fit that considers chemisorption, typically to a hydrous metal oxide surface, as rate controlling. This process is observed to be independent of solution composition and strain processing regime. This behaviour reflects complexation to the passivating surface chromium oxide film, and as determined by depth elemental analysis, effectively inhibits contaminant migration into the bulk material. Environment chemistry and microstructural variables that destabilise the Cr-rich passive film however reduces the passive layer capabilities to effectively inhibit fission product bulk diffusion. The importance of corrosion phenomena towards radionuclide sorption processes necessitates the consideration of metallurgical and chemical factors during the implementation of decontamination approaches to treat affected plant material at nuclear licenced sites. LIBS was found to be a satisfactory technique for measurement of Sr sorbed to steel but Cs could not be detected at the concentrations used in this experimentation. Furthermore, EDX and TOF-SIMS elemental mapping indicated ablated material may be redistributed into the crater profile during elemental analysis. This process has clear implications for the deployment of LIBS for in situ characterisation of nuclear materials as the uncontrolled redistribution of radioactive material certainly violates decommissioning principles.

Although targets for renewable energy exist in Sweden, developing wind energy has proven to be challenging for developers. This is due in part to the demands made by authorities for monetary amounts to be set aside to take care of wind turbine dismantling and site restoration costs at the end of their lifecycle. There has been a large degree of uncertainty surrounding the amounts being demanded and the level to which sites must be restored, partially due to a lack of guidelines. Coupled with ambiguity, there has been a tendency by authorities and developers to use figures from previous high court decisions and previous permit applications to project decommissioning costs for current applications.This thesis evaluates seven different wind farm decommissioning scenarios using a model developed to estimate future costs, with the turbine model and the quantity of turbines being the parameters that vary. The model uses data from numerous sources, including real case decommissioning projects and figures from an existing model that had already been used to forecast costs in Sweden. One of the assumptions of the model developed is that scrap metals in wind turbines will have a residual value when decommissioning occurs; this was not allowed for in a recent decision made by a county administrative board following an environmental high court decision. An argument is made to justify that a minimum scrap value for wind turbines should be considered, based on the findings of the model. A further case is made to allow for the security bonds to be paid over an extended period of time, considering the initial value of wind farms.The results of the model show that the turbine model has an impact on the decommissioning costs and the potential residual value that can be obtained. In addition, the quantity of the wind turbines has a considerable effect on the decommissioning costs. These results suggest that each wind development project should be treated on a case-by-case basis using a calculation-based approach when determining the cost for a security bond. Recommendations for future research include considering wind farm location in the model.

No description available.

Due to a lack of knowledge and experience the best approach to deal with wind farm decommissioning has yet to be determined. To fill this void, this paper analyzed the current status in terms of regulations and cost, regarding the decommissioning in Italy and Sweden.   In order to make a comparison between these two countries, the available research papers and reports on the decommissioning cost assessment, removal methods and regulations were thoroughly investigated. Moreover, detailed estimated dismantling cost data was obtained from a wind farm in Italy.   The Italian cost data were compared with data collected in Sweden and along with them, the regulations and legislations related to how these costs have to be assessed as well as what developers are required to do regarding the decommissioning in the permit issuance were included.   The results of this research show that in decommissioning cost assessment both countries does not allow developers to include the possible revenues due to the scraps and to the recycling of components, although totally different methods are pursued.   Some kind of security to ensure that decommissioning occurs is required, normally a bond. The bond amount is a debt investment in which an investor loans money to an entity (corporate or governmental) that borrows the funds for a defined period of time at a fixed interest rate. In Italy the bond requirements are generally high and it has to be paid completely for the permit issuance. In order to develop significant projects, this kind of approach leads to discourage small investors.   On the contrary, in Sweden the current amount of 300.000 SEK per turbine according to the court precedent, the most widespread during the approval of the permit, is definitely low and represent a level playing field for every investor. Swedish regulations are also more flexible and only in the 28% of the cases studied between the years 2009 and 2012, the entire amount of the bond had to be assured before the installation. However, the malleability with regard to wind farms that do not need to provide any security, together with the low bond amount might endanger the decommissioning accomplishment.

The decommissioning of nuclear power stations will lead to the production of a number of contaminated components. The materials produced will consist of process and structural wasteforms. Before this waste can be disposed it will be necessary to obtain a full inventory of those radionuclides contained in those wastes. This will be necessary to ensure that the waste is handled in a suitable manner and that full information is available so that reliable risk assessment can be carried out on the proposed disposal site. A number of radionuclides have been highlighted as significant in terms if their halflife, terrestrial mobility and predicted levels in decommissioning wastes. A selection of these radionuclides have been investigated, and methods developed for their determination in concrete. It was a requirement of this work that the methods developed were robust and that the minimum detectable amount was below that of the de minimis of O.4Bq g-1.

Dans le cadre des opérations de démantèlement des centrales nucléaires UNGG (Uranium Naturel Graphite Gaz), l’occurrence de phénomènes indésirables, tels que l’inflammation et l’explosion de poudres, ne peut pas être systématiquement exclue. Plus particulièrement, le risque d’inflammation et d’explosion de poussières de graphite, pur ou mélangé avec des impuretés métalliques telles que des particules de magnésium ou de fer, nécessite d’être évalué de façon plus approfondie. Les travaux de cette thèse s’inscrivent donc dans ce contexte et ont deux objectifs principaux : l’évaluation expérimentale de l’explosivité et sa modélisation. 1. L’évaluation expérimentale de l’explosivité des poudres d'intérêt a été réalisée tant en termes de sensibilité à l’inflammation, en couche et en nuage, que de sévérité à l’explosion. En effet, les caractéristiques explosives d’une poussière ou d’un mélange sont fortement influencées par plusieurs paramètres. Ils dépendent d’une part des conditions opératoires, tels que la turbulence, la température et l'énergie d’inflammation, et d’autre part, des propriétés physico-chimiques et de la composition des matériaux. Cette étude s’est focalisée sur des poudres pures de graphite, de magnésium et de fer de taille micrométrique et sur leurs mélanges, dans un éventail de concentrations d’intérêt industriel. Nous avons constaté que l’introduction de métaux peut changer en premier lieu l’étape limitant la vitesse de combustion du graphite. Tout d’abord, les phénomènes cinétiques limitant de l’oxydation du graphite ont été distingués de ceux des métaux (respectivement, réaction hétérogène ou flamme de diffusion gazeuse). En deuxième lieu, il est apparu que la flamme peut être épaissie par la présence du rayonnement lors de la combustion du métal, alors que ce phénomène est négligeable pour le graphite pur. Enfin, la turbulence initiale du nuage de poussière peut être elle aussi modifiée par l'ajout d'une deuxième poudre en vue des caractéristiques granulométriques et de densité différentes. Une étude paramétrique a donc été réalisée afin d'évaluer l'explosibilité des mélanges considérés en prenant en compte les effets de l'humidité relative des poudres, de leur distribution granulométrique, de la puissance de la source d'ignition, de la turbulence initiale du milieu et de la composition. Pour ce faire, nous avons utilisé à la fois des appareils et des technologies conventionnelles, tels que la sphère de 20 litres, la vélocimétrie par images de particules et la thermogravimétrie, mais également des nouvelles installations dédiées à la caractérisation des écoulements turbulents transitoires lors de la dispersion des poudres dans la sphère d'explosion et à l’étude de la propagation d’une flamme en milieu semi-confiné. Il a été clairement démontré que l'ajout de poudres métalliques influence l'aptitude à enflammer le nuage de poussière. L'énergie et la température minimale d'inflammation diminuent fortement lorsque le magnésium est ajouté au graphite ; ce phénomène est moins sensible pour les particules de fer. De plus, la sévérité de l'explosion augmente avec une telle addition. Cet effet de promotion est particulièrement visible sur la cinétique de combustion. 2. La modélisation du phénomène explosif a été réalisée à l’aide de la simulation numérique afin d’estimer une vitesse de propagation de flamme laminaire et d’étudier les effets induits par des facteurs spécifiques d’intérêt industriel, tels que le diamètre des particules ou la concentration en poudre. L’intérêt d’estimer une vitesse de flamme laminaire réside dans son caractère pseudo-intrinsèque. En connaissant les caractéristiques turbulentes d’un milieu industriel complexe, ce paramètre donne la possibilité d’obtenir une vitesse de propagation de flamme turbulente propre au milieu réel et donc d’estimer les effets d’une explosion potentielle. Les résultats expérimentaux ont été utilisés afin de valider le modèle numérique développé / During the decommissioning operations of the UNGG (Natural Uranium Graphite Gas) nuclear plants, the occurrence of undesirable phenomena, such as dust ignition and explosion, cannot be systematically neglected. In particular, graphite powders, pure or mixed with metals impurities present on the sites, such as magnesium or iron, can represent a potential risk that needs to be further evaluated. This work falls within this context and has two main objectives: the experimental evaluation of the explosion severity and its modeling. 1. The experimental evaluation of the explosivity of such a powders has been carried out both in terms of ignition sensitivity, of dust layer and cloud, and explosion severity. Actually, explosive characteristics of a dust or of a mixture are strongly influenced by several parameters. They depend on the one side on the operating conditions, such as turbulence, temperature and energy of the ignition source, and on the other side, of course, on the materials physicochemical properties and composition. This study focuses on pure micronized powders of graphite, magnesium, and iron and on their mixtures, in a concentration range of industrial interest. It has been demonstrated that the introduction of metals can change, first of all, the rate limiting step of the graphite combustion. Therefore, the kinetic phenomena controlling the graphite oxidation have been distinguished from those of metals (oxygen diffusion or metal vaporization). Secondly, the flame can be thickened by the presence of the radiation during the metal combustion, while this phenomenon is negligible for pure graphite. Finally, the initial turbulence of the dust cloud can be modified by adding a second powder because of the different granulometric characteristics and density. A parametric study was conducted to evaluate the mixtures explosivity taking into account the effects of the relative humidity, the particle size distribution of the powders, the power of the ignition source, the initial turbulence and the composition of the mixture. In order to do this, we used both conventional devices and technologies, such as 20-liters explosion sphere, the particles image velocimetry and the thermogravimetry, but also new facilities dedicated to the characterization of the transient turbulent flow during the dispersion of the powders in the explosion sphere and to study the propagation of a semi-confined flame. It was clearly demonstrated that the addition of metals influences the ability to ignite the dust cloud. The minimum ignition energy and temperature greatly decrease when magnesium powder is added to graphite dust; this phenomenon is less remarkable for iron particles. In addition, the severity of the explosion increases with such an addition. This promotion effect is particularly significant on the combustion kinetics. 2. The modeling of the explosive phenomenon has been performed using numerical simulations in order to estimate a laminar flame propagation velocity and to study the effects induced by specific factors of industrial interest, such as the particle size or the powder concentration. The interest in determining a laminar flame velocity is its pseudo-intrinsic character. Once known the turbulent characteristics of a complex industrial environment, this parameter gives the opportunity to obtain a turbulent flame propagation velocity in a real environment and, therefore, to estimate the effects of a potential explosion. Experimental results were used to validate the numerical model developed during this work

Made available in DSpace on 2014-10-09T12:55:29Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:54Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:55:29Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:54Z (GMT). No. of bitstreams: 0 / O Instituto de Pesquisas Energéticas e Nucleares (IPEN) é uma Instituição de Pesquisas e Desenvolvimento que está localizada dentro de uma área densamente povoada, na cidade de São Paulo. O ciclo do combustível nuclear foi desenvolvido desde o yellow cake até o enriquecimento dentro do IPEN. Após esta etapa, toda técnica foi repassada à iniciativa privada e à Marinha do Brasil (CTM/SP). Algumas usinas do ciclo do combustível estavam em nível semi-industrial, com produção de mais de 20 kg.h-1. Como Instituto de Pesquisa, o IPEN cumpriu sua função no ciclo de combustível, que é desenvolver e repassar a tecnologia. Com a necessidade de se encontrar um lugar para implantar novos projetos, o espaço físico escolhido foi no local onde se achava a Usina de Produção de Hexafloreto de Urânio (UF6), que estava inativa há alguns anos e apresentava riscos de vazamento em potencial, o que poderia ocasionar agressão ao meio ambiente e riscos de acidentes graves. O descomissionamento desta usina exigiu um cuidadoso planejamento por ser um trabalho nunca realizado no Brasil, numa unidade desse tipo com riscos eminentes, visto que envolvia o gás fluoridetro (HF) e ácido fluorídrico, solução altamente corrosiva. Fizeram-se avaliações criteriosas e desenvolveram-se equipamentos especiais, com o intuito de evitar vazamentos e riscos de acidente. No trabalho de descomissionamento, foram obedecidas as normas da CNEN em todas as operações realizadas. Foi calculado o impacto ambiental, que se mostrou desprezível sendo que as doses de radiação, após o térmíno do trabalho, estavam dentro dos limites de público, podendo a área ser liberada para nova utilização. O tipo de descomissionamento realizado foi de remoção completa, retirando-se todos os materiais e equipamentos. Todos os rejeitos foram tratados e/ou armazenados em instalações adequadas. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

This work is focused on the issue of creation of reserves to cover the costs of decommissioning of nuclear installations. These costs arise from the need to prevent exposure to radioactivity and other pollutants that adversely affect the environment and human health. The thesis describes various systems of decommissioning of nuclear installations and the creation of reserves in selected countries - the Czech Republic, United Kingdom, Finland and France. The analytical part of the work deals with comparative analysis of the creation of reserves for decommissioning of nuclear facilities in selected countries and their subsequent evaluation. The work is a basis for optimizing the system for establishing reserves for decommissioning of nuclear facilities in the Czech Republic.