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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

High-Resolution Seismics Methods Applied to Till Covered Hard Rock Environments

Bergman, Björn January 2005 (has links)
Reflection seismic and seismic tomography methods can be used to image the upper kilometer of hard bedrock and the loose unconsolidated sediments covering it. Developments of these two methods and their application, as well as identifying issues concerning their usage, are the main focus of the thesis. Data used for this development were acquired at three different sites in Sweden, in Forsmark 140 km north of Stockholm, in the Oskarshamn area in southern Sweden, and in the northern part of the Siljan Ring impact crater area. The reflection seismic data were acquired with long source-receiver offsets relative to some of the targeted depths to be imaged. In the initial processing standard steps were applied, but the uppermost part of the sections were not always clear. The longer offsets imply that pre-stack migration is necessary in order to image the uppermost bedrock as clearly as possible. Careful choice of filters and velocity functions improve the pre-stack migrated image, allowing better correlation with near-surface geological information. The seismic tomography method has been enhanced to calculate, simultaneously with the velocity inversion, optimal corrections to the picked first break travel times in order to compensate for the delays due to the seismic waves passing through the loose sediments covering the bedrock. The reflection seismic processing used in this thesis has produced high-quality images of the upper kilometers, and in one example from the Forsmark site, the image of the uppermost 250 meters of the bedrock has been improved. The three-dimensional orientation of reflections has been determined at the Oskarshamn site. Correlation with borehole data shows that many of these reflections originate from fracture zones. The developed seismic tomography method produces high-detail velocity models for the site in the Siljan impact area and for the Forsmark site. In Forsmark, detailed estimates of the bedrock topography were calculated with the use of the developed tomography method.
2

High-Resolution Seismics Methods Applied to Till Covered Hard Rock Environments

Bergman, Björn January 2005 (has links)
<p>Reflection seismic and seismic tomography methods can be used to image the upper kilometer of hard bedrock and the loose unconsolidated sediments covering it. Developments of these two methods and their application, as well as identifying issues concerning their usage, are the main focus of the thesis. Data used for this development were acquired at three different sites in Sweden, in Forsmark 140 km north of Stockholm, in the Oskarshamn area in southern Sweden, and in the northern part of the Siljan Ring impact crater area.</p><p>The reflection seismic data were acquired with long source-receiver offsets relative to some of the targeted depths to be imaged. In the initial processing standard steps were applied, but the uppermost part of the sections were not always clear. The longer offsets imply that pre-stack migration is necessary in order to image the uppermost bedrock as clearly as possible. Careful choice of filters and velocity functions improve the pre-stack migrated image, allowing better correlation with near-surface geological information.</p><p>The seismic tomography method has been enhanced to calculate, simultaneously with the velocity inversion, optimal corrections to the picked first break travel times in order to compensate for the delays due to the seismic waves passing through the loose sediments covering the bedrock.</p><p>The reflection seismic processing used in this thesis has produced high-quality images of the upper kilometers, and in one example from the Forsmark site, the image of the uppermost 250 meters of the bedrock has been improved. The three-dimensional orientation of reflections has been determined at the Oskarshamn site. Correlation with borehole data shows that many of these reflections originate from fracture zones. </p><p>The developed seismic tomography method produces high-detail velocity models for the site in the Siljan impact area and for the Forsmark site. In Forsmark, detailed estimates of the bedrock topography were calculated with the use of the developed tomography method.</p>
3

Modelling water and solute flows at land-sea and land-atmosphere interfaces under data limitations

Shibuo, Yoshihiro January 2007 (has links)
<p>Water and vapour flows from land to sea and the atmosphere are important for water resources, coastal ecosystems and climate. This thesis investigates possible methods for modelling these flows under often encountered unmonitored hydrological conditions and data limitations. Two contrasting types of drainage basin and associated data limitation/availability cases are considered: the Swedish unmonitored near-coastal catchment areas Forsmark and Simpevarp, for which detailed spatial but not much temporal variability data is available; and the much larger Aral Sea Drainage Basin (ASDB), for which spatial hydrological information is limited, while there is relatively well-known temporal change occurring in the Aral Sea itself and in the land and water use of the region over the last 50 years.</p><p>The hydrologic modelling for the Forsmark and Simpevarp catchment areas showed that the relatively large focused stream flows, and the mean values and total sums of the diffuse small stream-groundwater flow fields in between the large stream flows from land to sea are largely constrained by the catchment hydrological balances and relatively robust and certain to estimate. The ASDB hydrologic modelling indicated an evapotranspiration return flow to the atmosphere from the irrigation water input on irrigated land that is much higher than previous estimates in atmospheric modelling, implying possible considerably larger than previously estimated non-local water and climate effects of the world’s irrigated areas. The more detailed groundwater-seawater dynamics modelling carried out for the coastal parts of the ASDB showed that regional topography and bathymetry largely influence coastal water fluxes during sea level lowering, with the Aral Sea shrinkage decreasing the seawater intrusion risk into the coastal groundwater considerably more for steeper than for flatter coastal topography parts of the region.</p>
4

Modelling water and solute flows at land-sea and land-atmosphere interfaces under data limitations

Shibuo, Yoshihiro January 2007 (has links)
Water and vapour flows from land to sea and the atmosphere are important for water resources, coastal ecosystems and climate. This thesis investigates possible methods for modelling these flows under often encountered unmonitored hydrological conditions and data limitations. Two contrasting types of drainage basin and associated data limitation/availability cases are considered: the Swedish unmonitored near-coastal catchment areas Forsmark and Simpevarp, for which detailed spatial but not much temporal variability data is available; and the much larger Aral Sea Drainage Basin (ASDB), for which spatial hydrological information is limited, while there is relatively well-known temporal change occurring in the Aral Sea itself and in the land and water use of the region over the last 50 years. The hydrologic modelling for the Forsmark and Simpevarp catchment areas showed that the relatively large focused stream flows, and the mean values and total sums of the diffuse small stream-groundwater flow fields in between the large stream flows from land to sea are largely constrained by the catchment hydrological balances and relatively robust and certain to estimate. The ASDB hydrologic modelling indicated an evapotranspiration return flow to the atmosphere from the irrigation water input on irrigated land that is much higher than previous estimates in atmospheric modelling, implying possible considerably larger than previously estimated non-local water and climate effects of the world’s irrigated areas. The more detailed groundwater-seawater dynamics modelling carried out for the coastal parts of the ASDB showed that regional topography and bathymetry largely influence coastal water fluxes during sea level lowering, with the Aral Sea shrinkage decreasing the seawater intrusion risk into the coastal groundwater considerably more for steeper than for flatter coastal topography parts of the region.
5

The sorption of uranium(VI) and neptunium(V) onto surfaces of selected metal oxides and alumosilicates studied by in situ vibrational spectroscopy

Müller, Katharina 11 November 2010 (has links) (PDF)
The migration behavior of actinides and other radioactive contaminants in the environment is controlled by prominent molecular phenomena such as hydrolysis and complexation reactions in aqueous solutions as well as the diffusion and sorption onto minerals present along groundwater flow paths. These reactions significantly influence the mobility and bioavailability of the metal ions in the environment, in particular at liquid-solid interfaces. Hence, for the assessment of migration processes the knowledge of the mechanisms occurring at interfaces is crucial. The required structural information can be obtained using various spectroscopic techniques. In the present study, the speciation of uranium(VI) and neptunium(V) at environmentally relevant mineral – water interfaces of oxides of titania, alumina, silica, zinc, and alumosilicates has been investigated by the application of attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy. Moreover, the distribution of the hydrolysis products in micromolar aqueous solutions of U(VI) and Np(V/VI) at ambient atmosphere has been characterized for the first time, by a combination of ATR FT-IR spectroscopy, near infrared (NIR) absorption spectroscopy, and speciation modeling applying updated thermodynamic databases. From the infrared spectra, a significant change of the U(VI) speciation is derived upon lowering the U(VI) concentration from the milli- to the micromolar range, strongly suggesting the dominance of monomeric U(VI) hydrolysis products in the micromolar solutions. In contradiction to the predicted speciation, monomeric hydroxo species are already present at pH ≥ 2.5 and become dominant at pH 3. At higher pH levels (> 6), a complex speciation is evidenced including carbonate containing complexes. For the first time, spectroscopic results of Np(VI) hydrolysis reactions are provided in the submillimolar concentration range and at pH values up to 5.3, and they are comparatively discussed with U(VI). For both actinides, the formation of similar species is suggested at pH ≤ 4, whereas at higher pH, the infrared spectra evidence structurally different species. At pH 5, the formation of a carbonate-containing dimeric complex, that is (NpO2)2CO3(OH)3−, is strongly suggested, whereas carbonate complexation occurs only under more alkaline conditions in the U(VI) system. The results from the experiments of the sorption processes clearly demonstrate the formation of stable U(VI) surface complexes at all investigated mineral phases. This includes several metal oxides, namely TiO2, Al2O3, and SiO2, serving as model systems for the elucidation of more complex mineral systems, and several alumosilicates, such as kaolinite, muscovite and biotite. From a multiplicity of in situ experiments, the impact of sorbent characteristics and variations in the aqueous U(VI) system on the sorption processes was considered. A preferential formation of an inner-sphere complex is derived from the spectra of the TiO2 and SiO2 phases. In addition, since the in situ FT-IR experiments provide an online monitoring of the absorption changes of the sorption processes, the course of the formation of the U(VI) surface complexes can be observed spectroscopically. It is shown that after prolonged sorption time on TiO2, resulting in a highly covered surface, outer-sphere complexation predominates the sorption processes. The prevailing crystallographic modification, namely anatase and rutile, does not significantly contribute to the spectra, whereas surface specific parameters, e.g. surface area or porosity are important. A significant different surface complexation is observed for Al2O3. The formation of inner-spheric species is assumed at low U(VI) surface coverage which is fostered at low pH, high ionic strength and short contact times. At proceeded sorption the surface complexation changes. From the spectra, an outer-spheric coordination followed by surface precipitation or polymerization is deduced. Moreover, in contrast to TiO2, the appearance of ternary U(VI) carbonate complexes on the γ-Al2O3 surface is suggested. The first results of the surface reactions on more complex, naturally occurring minerals (kaolinite, muscovite and biotite) show the formation of U(VI) inner-sphere sorption complexes. These findings are supported by the spectral information of the metal oxide surfaces. In this work, first spectroscopic results from sorption of aqueous Np(V) on solid mineral phases are provided. It is shown that stable inner-sphere surface species of NpO2+ are formed on TiO2. Outer-sphere complexation is found to play a minor role due to the pH independence of the sorption species throughout the pH range 4 – 7.6. The comparative spectroscopic experiments of Np(V) sorption onto TiO2, SiO2, and ZnO indicate structurally similar bidentate surface complexes. The multiplicity of IR spectroscopic experiments carried out within this study yields a profound collection of spectroscopic data which will be used as references for future investigations of more complex sorption systems in aqueous solution. Furthermore, from a methodological point of view, this study comprehensively extends the application of ATR FT-IR spectroscopic experiments to a wide range in the field of radioecology. The results obtained in this work contribute to a better understanding of the geochemical interactions of actinides, in particular U(VI) and Np(V/VI), in the environment. Consequently, more reliable predictions of actinides migration which are essential for the safety assessment of nuclear waste repositories can be performed. / Das Migrationsverhalten von Aktiniden und anderen radioaktiven Schadstoffen in der Umwelt wird von wichtigen molekularen Prozessen entlang der Grundwasserfließwege reguliert. Dazu gehören sowohl die Hydrolyse und Komplexierung in wässrigen Lösungen als auch Diffusion und Sorption der Schwermetalle an Mineralen. Diese Reaktionen beeinflussen entscheidend die Mobilität und Bioverfügbarkeit der Metallionen in der Umwelt, insbesondere an den fest-flüssig Grenzflächen. Genaue Kenntnisse über die an diesen Grenzflächen stattfindenden Mechanismen sind somit entscheidend, um Migrationsprozesse verlässlich abschätzen zu können. Die benötigten strukturellen Informationen können mit verschiedenen spektroskopischen Techniken ermittelt werden. Das Ziel der vorliegenden Arbeit war die Untersuchung der Speziation von Uran(VI) und Neptunium(V) an umweltrelevanten Grenzflächen von Oxiden des Titans, Aluminiums, Siliziums und Zinks und von Alumosilikaten mittels ATR FT-IR Spektroskopie. Des Weiteren wurde die Verteilung aquatischer Spezies in mikromolaren Lösungen des U(VI) und Np(V/VI) unter Normalbedingungen charakterisiert. Diese erstmalige Untersuchung wurde mit einer Kombination aus Speziationsmodellierung unter Anwendung aktueller thermodynamischer Daten und ATR FT-IR und NIR Absorptionsspektroskopie realisiert. Die Infrarotspektren zeigen eine deutliche Änderung der Speziesverteilung im Konzentrationsverlauf vom millimolaren zum mikromolaren Bereich. Dies verweist auf die Bildung monomerer U(VI) Hydrolyseprodukte. Im Gegensatz zu berechneten Speziationen werden diese monomeren Komplexe schon bei pH ≥ 2,5 gebildet und dominieren die Speziation bei pH 3. Bei höheren pH-Werten (> 6) konnte eine komplexe Speziesverteilung mit Anteilen von Karbonatkomplexen nachgewiesen werden. Erstmals konnten im Rahmen dieser Arbeit spektroskopische Befunde der Hydrolysereaktionen des Np(VI) im submillimolaren Konzentrationsbereich bis pH 5,3 erhalten werden. Diese wurden im Vergleich mit der U(VI) Speziation diskutiert. Obwohl im sauren Bereich (pH ≤ 4) die Bildung ähnlicher Komplexe nachgewiesen wurde, zeigen die bei höheren pH-Werten erhaltenen Spektren eine unterschiedliche Speziesverteilung. Im Gegensatz zum U(VI) bildet das Np(VI) schon bei pH 5 karbonathaltige aquatische Spezies wie (NpO2)2CO3(OH)3−. Die Ergebnisse der Sorptionsexperimente von U(VI) zeigen die Bildung stabiler Oberflächenkomplexe an allen untersuchten Mineralphasen. Dies umfasst mehrere als Modellsystem dienende Metalloxide wie TiO2, Al2O3 und SiO2, als auch komplexere Alumosilikate wie Kaolinit, Muskovit und Biotit. Für eine detaillierte Charakterisierung der Oberflächenkomplexe wurde eine Vielzahl von in situ Sorptionsexperimenten durchgeführt, die den Einfluss unterschiedlicher Parameter der mineralischen Phase als auch des wässrigen U(VI) Systems berücksichtigen. Die bevorzugte Bildung von innersphärischen Komplexen an TiO2 und SiO2 wird aus den spektroskopischen Daten abgeleitet. Da die in situ FT-IR Spektroskopie eine kontinuierliche Registrierung der Absorptionsänderungen während der ablaufenden Sorptionsprozesse erlaubt, kann somit der Verlauf dieser Prozesse quasi in Echtzeit spektroskopisch verfolgt werden. Es konnte gezeigt werden, dass mit fortschreitender Sorptionsdauer, d.h. bei hohen Beladungsdichten, die Bildung einer weiteren außersphärischen Spezies die Sorption dominert. Die vorliegende kristallographische Modifikation, Anatas und Rutil, ist nicht maßgeblich für das Auftreten unterschiedlicher Sorptionsprozesse verantwortlich, obwohl Parameter wie die spezifische Oberfläche und die Porosität für den Sorptionsprozess von Bedeutung sind. Deutlich verschiedene Oberflächenreaktionen werden für Al2O3 beobachtet. Aus den Spektren kann die Ausbildung einer innersphärischen Spezies bei sehr niedrigen U(VI) Beladungen, niedrigen pH-Werten, hohen Ionenstärken und kurzen Kontaktzeiten abgeleitet werden. Bei fortschreitender Sorption ändert sich die Art der Oberflächenkomplexe. Zunächst bilden sich außersphärische Spezies, während im weiteren Verlauf die Spektren auf eine beginnende Oberflächenausfällung bzw. Polymerisation hinweisen. Weiterhin wird das Auftreten von ternären U(VI) Karbonatkomplexen an γ-Al2O3 aus den spektroskopischen Daten abgeleitet. Die ersten Ergebnisse der Sorptionsexperimente an komplexeren, natürlich auftretenden Mineralphasen (Kaolinit, Muskovit und Biotit) zeigen eine bevorzugte Ausbildung von innersphärischen U(VI) Komplexen. Diese Resultate werden durch die spektralen Befunde der Experimente der Metalloxide gestützt. Erstmalig werden in dieser Arbeit spektroskopische Ergebnisse der Sorptionsprozesse von wässrigen Np(V) an verschiedenen Mineralphasen präsentiert. Wie U(VI) bildet Np(V) stabile innersphärische Oberflächenkomplexe an TiO2. Die Speziesverteilung an der TiO2 Oberfläche ist im pH Bereich 4 – 7,6 konstant. Daher ist zu erwarten, dass eine außersphärische Komplexierung hier nur eine untergeordnete Rolle spielt. Der Vergleich von Spektren der Np(V) Sorptionskomplexe an TiO2, SiO2 und ZnO weist auf die Bildung strukturell ähnlicher bidentater Komplexe hin. Die Vielzahl der hier vorgestellten infrarotspektroskopischen Experimente bietet eine fundierte Sammlung spektroskopischer Daten, die für zukünftige Untersuchungen komplexer aquatischer und mineralischer Systeme unerlässlich ist. Gleichzeitig wurde der Anwendungsbereich der ATR FT-IR Technik auf dem Gebiet der Radioökologie umfassend erweitert. Die im Rahmen dieser Arbeit gewonnenen Ergebnisse tragen zu einem besseren Verständnis der geochemischen Wechselwirkungen von Aktiniden, im Speziellen von U(VI) und Np(V) in der Umwelt bei. Damit unterstützen sie den Aufklärungsprozess der Migration von radioaktiven Kontaminationen und dienen als Grundlage für zuverlässige Prognosen für die Sicherheitsbewertung von Endlagern für nukleare Abfälle.
6

Evaluation of a concrete plug : From the Dome Plug Experiment DOMPLU at Äspö HRL

Kristiansson, Anders January 2014 (has links)
In SKB’s Äspö Hard Rock Laboratory (HRL) a full scale test of a concrete plug,part of a sealing structure for the depository of spent nuclear fuel, has been carriedout. The aim of this thesis is to evaluate the behavior of the concrete plug and howit corresponds to assumptions made during the design. The concrete plug is domeshaped, un-reinforced and casted in situ with low-pH concrete. It will be exposed tohigh water and swelling pressures and designed for a life span of 100 years. Duringthe first years it shall also prevent water leakage from the inside of the depositiontunnel. Before the pressure is applied, the concrete plug is assumed to de-bond fromthe rock due to autogenous and cooling shrinkage. The gap between the concrete androck is then grouted during cooling and the concrete plug will hence be prestressedwhen the cooling is stopped. The concrete plug is analyzed with the measurement data from the full scale testwith comparisons to results from finite element simulations. The performed measurementsinclude form pressure, internal strain and temperature, concrete plugdisplacements in the tunnel alignment, displacements relative to the rock and ambienttemperatures. Two assumptions have been made during the evaluation; fullbond to the rock or no bond to the rock. The results are also compared to twosimilar experiment that were previously performed. The results indicate that the concrete did de-bond from the rock before grouting tosome extent. It is plausible that a selective de-bonding was obtained. Due to highwater leakage, were cables for the measurement equipment are drawn out from theconcrete plug, the concrete plug was not exposed to the planed maximum pressureload. Results indicate that a water pressure is acting on the concrete plug frominside the rock slot which was not assumed during the design. / I SKB:s Äspölaboratoriet har ett fullskaleförsök på en betongplugg, del av ett pluggsystemför förvaret av kärnavfall, utförts. Syftet med denna uppsats var attutvärdera betongpluggens beteende under fullskaleförsöket och hur det förhållersig till gjorda antaganden under dess utformning. Betongpluggen är kupolformad,oarmerad och platsgjuten med låg-pH-betong. Höga vatten- och svälltryck kommerverka på betongpluggen som är utformad för en livstid på 100 år. Under deförsta åren ska den även motverka läckage från insidan av deponeringstunneln. Innantrycklasten läggs på är det antaget att betongpluggen släpper från berget till följd avautogen krympning och kylning. Utrymmet mellan betongen och berget injekterasoch betongpluggen kommer således vara förspänd efter att kylningen upphört. Betongpluggen är analyserad med mätdata från fullskaleförsöket som jämförts medresultat från finita element analyser. Mätningarna inkluderar formtryck, inre töjningaroch temperaturer, deformationer i tunnelriktningen, deformationer relativt bergetoch lufttemperatur utanför betongpluggen. Två antaganden har gjorts under utvärderingen;att betongen är fast i berget eller att den är fri från berget. Resultaten jämförsäven med två liknande fullskaleförsök som utförts tidigare. Resultaten tyder på att betongpluggen till viss del släppt från berget innan injekteringen.Det är troligt att den släppt på vissa ställen och på andra inte. På grundav för högt vattenläckage där de ingjutna mätinstrumentens kabelgenomföring utförts,kunde inte betongpluggen belastas till det maximala tryck som var planerat.Resultaten tyder på att ett vattentryck verkar på betongpluggen mellan berget ochbetongen vilket inte var antaget under konstruktionen.
7

Extractive Violence on Indigenous Country : sami and Aboriginal Views on Conflicts and Power Relations with Extractive Industries / Extraktivt våld på urfolks marker : konflikter och maktrelationer mellan utvinningsindustrier och urfolk i Sverige och Australien

Sehlin MacNeil, Kristina January 2017 (has links)
Asymmetrical conflicts and power relations between extractive industries and Indigenous groups often have devastating consequences for Indigenous peoples. Many Indigenous groups are struggling to maintain their lands as Indigenous perspectives on connection to Country are frequently undervalued or dismissed in favour of extractivist ideologies. While this conflicted interface has been researched in various parts of the world, studies exploring conflicts and power relations with extractive industries from Indigenous perspectives are few. This thesis is an international comparison aiming to illuminate situations of conflict and asymmetrical power relations caused by extractivism on Indigenous lands from new viewpoints. By drawing on two single case studies, the situations for Laevas reindeer herding Sami community in northern Sweden and Adnyamathanha Traditional Owners in South Australia are compared and contrasted. Yarning (a form of interviewing) is used as a method for data collection and in order to stay as true as possible to the research participants’ own words a number of direct quotes are used. The analysis employs peace researcher Johan Galtung’s concepts of cultural and structural violence as analytical tools to further explore the participants’ experiences of interactions with extractive industries and industrial proponents, including governments. In addition, the thesis introduces the concept of extractive violence as a complement to Galtung’s model. Extractive violence is defined as a form of direct violence against people and/or animals and nature caused by extractivism, which predominantly impacts peoples closely connected to land. The concepts of structural and cultural violence are understood as unjust societal structures and racist and discriminating attitudes respectively. A number of main themes could be identified in the research participants’ narratives. However, the most prominent on both continents was connections to Country and the threat that extractive violence posed to these connections. The results show that although the expressions of cultural, structural and extractive violence experienced by the two Indigenous communities varied, the impacts were strikingly similar. Both communities identified extractive violence, supported by structural and cultural violence, as threats to the continuation of their societies and entire cultures. Furthermore, the results suggest that in order to address violence against Indigenous peoples and achieve conflict transformation, Indigenous and decolonising perspectives should be heard and taken into account. / Konflikter och maktrelationer mellan utvinningsindustrier och urfolksgrupper får ofta förödande konsekvenser för urfolken. På grund av assymetriska maktförhållanden mellan urfolk och majoritetssamhällen som råder på de flesta ställen i världen utsätts många urfolk systematiskt för rättighetskränkningar. Många urfolksgrupper kämpar idag för att bevara sina marker eftersom urfolks perspektiv och kopplingar till marken ofta förminskas eller ignoreras när de står i motsättning till extraktiva ideologier. Även om extraktivism och påverkan på urfolk och urfolksgrupper varit fokus för tidigare studier saknas forskning som utgår från urfolkens perspektiv. Denna avhandling är en internationell jämförelse med syfte att, från nya synvinklar, belysa konfliktsituationer och asymmetriska maktrelationer som orsakats av extraktivism på urfolks marker. Avhandlingen jämför och kontrasterar två fallstudier som utförts med Laevas č earru (sameby) i norra Sverige och Adnyamathanha-folket i delstaten South Australia. I fallstudien som utförts tillsammans med Laevas č earru ingår en grupp av totalt sex forskningsdeltagare, fyra män och två kvinnor. Det var dock framför allt två forskningsdeltagare som intervjuades med anledning av den konfliktsituation mellan Laevas č earru och gruvbolaget LKAB, som står i fokus för artikel I i avhandlingen. I den australiska fallstudien, som utförts tillsammans med Adnyamathanha-folket, ingår en grupp av sju forskningsdeltagare bestående av fyra kvinnor och tre män. Denna studie, artikel II, behandlar Adnyamathanhafolkets kamp mot de australiska och sydaustraliska regeringarnas förslag om att inrätta kärnavfallsdepåer på Adnyamathanhas marker. För att inhämta material användes yarning (en typ av intervjumetod) och för att återge forskningsdeltagarnas ord så rättvisande möjligt inkluderades ett antal direktcitat i texterna. För att möjliggöra en mer djupgående analys av forskningsdeltagarnas upplevelser av konflikter med utvinningsindustrier och förespråkare för extraktivism, inklusive regeringar och stater, användes Johan Galtungs modell, känd som Galtungs våldstriangel, som analysverktyg. Galtungs modell innefattar strukturellt, kulturellt och direkt våld. Direkt våld definieras som fysiskt våld eller hot om fysiskt våld, strukturellt våld utgörs av orättvisa och diskriminerande samhällsstrukturer och kulturellt våld är de attityder som får det strukturella och således även det direkta våldet att te sig legitimt. Föreliggande avhandling introducerar även konceptet extraktivt våld som ett komplement till Galtungs modell där xvi det ersätter direkt våld. Jag definierar extraktivt våld som en typ av direkt våld mot människor och/eller djur och natur orsakat av extraktivism som framför allt påverkar människor med starka kopplingar till sina marker. Extraktivism förstås här som alla typer av aktiviteter som extraherar stora mängder av resurser från marker och människor, exempelvis gruvdrift, skogsbruk, fiske, lantbruk och turism. I forskningsdeltagarnas utsagor identifierades ett antal nyckelteman. Dessa teman uppvisade både likheter och skillnader beroende på deltagarnas olika situationer och förutsättningar. Det mest framträdande temat på båda kontinenterna var dock ”connection to Country” eller kopplingar till marken. Båda grupperna beskrev hur marken och deras förhållande till den innefattade historia, kunskap, traditioner och kultur. För Adnyamathanhagruppen var det mest centrala att rädda och bevara heliga platser som hotas av extraktivism och för Laevas č earru sågs renskötseln och bevarandet av markerna för renarnas skull som det mest väsentliga. Avhandlingens resultat visar att även om de former av kulturellt, strukturellt och extraktivt våld som forskningsdeltagarna upplevde varierade, var effekterna av våldet slående lika. Båda grupperna identifierade extraktivt våld, understött av strukturellt och kulturellt våld, som hot mot fortlevnaden av deras samhällen och kulturer. Resultaten pekar även på vikten av att urfolkens perspektiv inkluderas och blir hörda om konflikttransformering mellan utvinningsindustrier och urfolk ska kunna uppnås.
8

Studies on Modified Clay Additives to Impart Iodide Sorption Capacity to Bentonite in the Context of Safe Disposal of High Level Nuclear Waste

Sivachidambaram, S January 2012 (has links) (PDF)
It is a generally agreed internationally that high level nuclear wastes containing long-lived radioactive wastes should be disposed in deep and stable geological formations that are 500-1000 m below ground level. Deep geological disposal is based on the concept of multiple barriers to prevent deep ground-waters, present in almost all rock formations, from rapidly leaching the wastes and transporting radioactivity away from the repository. The multiple barrier system comprises of ‘engineered barriers’ that are constructed in the repository and ‘natural barriers’ in the surrounding geological environment. The engineered barrier components comprise of the vitrified solid waste, canister (to contain the vitrified waste), and a buffer or backfill material (clay or cement) that fills the annular space between the canister and the walls of the hole drilled in the floor of host-rock. The natural barrier is provided by the rocks and soils between the repository and earth’s surface. The canisters containing the hig level waste (HLW) upon placement in DGR need protection against tectonic activities and chemical attack by dissolved elements and from microbes. Densely compacted bentonite is identified suitable for this purpose owing to its large swell potential, low permeability, sufficient bearing capacity and high cation adsorption capacity. In the deep geological repository (DGR) for disposal of high level nuclear wastes, iodine-129 is one of the significant nuclides, owing to its long half-life (half life = 16 million years) and tendency to easily migrate out of the geological repository into the biosphere caused by its high solubility and poor sorption onto most geologic media. Bentonite buffer by virtue of negatively charged basal surface has negligible affinity for retention of iodide anions. Attempts have been made to improve the iodide retention capacity of bentonite by treating the clay with cationic polymers, this however occurs at the cost of reduced swelling ability of bentonite clay. The compacted bentonite employed in deep geological repositories must possess large swell potential to enable it to close fissures and cracks that form on drying of the expansive clay by the heat arising from the high level nuclear waste and thereby close pathways for migration of radionuclides (from breached canister) to the geo-environment. Therefore, it becomes important to identify an additive that enhances the iodide retention ability of the mix without significantly impairing its swelling ability. Based on the strong affinity of silver for iodide ions, the feasibility of mixing silver-kaolinite (termed AgK) clay with bentonite to improve the latter’s iodide sorption capacity and the impact of mixing AgK clay with bentonite on swelling ability of the mix forms one of the the focus of this thesis. Silver-kaolinite clay was prepared by heating 80% kaolinite + 20% silver nitrate mix at 400°C for 30 min, followed by washing (to remove unreacted silver nitrate) and oven-drying the resultant AgK clay. Physical mixing of AgK and bentonite was considered a viable proposition as small additions (10% to 20% on dry mass basis) besides imparting iodide sorption ability was expected to have minor influence on the swelling ability of the mix. As organo-bentonites are known to retain iodide ions, it was considered relevant to compare the iodide removal behaviour of AgK and organo¬bentonite clay. Hexadecylpyridinium-bentonite (termed as HDPy+B) is the organo¬bentonite examined in this thesis and is prepared by treating bentonite with hexadecylpyridinium chloride mono hydrate salt (C21H38ClN.H2O; molecular weight = 358.01). The hexadecylpyridinium chloride mono hydrate salt is a cationic quaternary ammonium compound and has been used by earlier researchers to prepare organo-bentonite for removal of iodide ions from aqueous solutions. The impact of mixing AgK and HDPy+B clays on the iodide retention and swelling behaviour of bentonite is also considered in the thesis. The mass-balance calculations, XRD analysis, X-ray photon emission survey spectrum and EPMA tests performed on kaolinite-silver nitrate mix/AgK/kaolinite specimen indicated that silver occurs as uniform coatings of AgO/Ag2O on kaolinite surface of the AgK specimen. The AgK clay has strong affinity for iodide ions reflected by the large distribution coefficients (Kd) values of 1367 and 293 mL/g at initial iodide concentrations of 750 mg/L and 1000 mg/L. Further, the sorption process was rapid, unaffected by the presence of co-ions, elevated temperature of sorption and was practically irreversible at range of pH conditions. The iodide retention by AgK is attributed to occurrence of hydrolysis and exchange reactions. On contacting the AgK with water, the AgO species hydrolyze to form AgOH; iodide ions are retained by replacing the hydroxyl group of AgOH leading to formation of AgI phase. The adsorption of HDPy+Cl- ions by bentonite occurs by replacement of the native exchangeable cations by HDPy+ ions and adsorption by van der Waals interactions between the organic cations and the clay surface. The adsorbed cationic polymer neutralize the negative charge of the clay surface. Zeta potential measurements of HDPy+B specimen indicated that adsorption of cationic polymer transforms the negatively charged clay particles into positively charged particles that favour anion adsorption. Sorption of iodide ions by HDPy+B specimen exhibits two distinct segments: 1) the iodide sorption increased rapidly at lower iodide concentration (91 mg/L to 475 mg/L) and are retained by Coulombic adsorption to the cationic groups contained in the loops and tails of the adsorbed polymer (primary adsorption sites) and 2) the relatively slower adsorption at higher iodide concentrations (larger than 475 mg/L) is attributed to exchange with chloride ions attached to HDPy+Cl-ion pair (secondary adsorption sites). The Kd values for iodide adsorption vary from 15 mL/g to 184 mL/g at initial iodide concentrations of 91 mg/L to 996 mg/L respectively. Comparing the iodide removal efficiencies of AgK and HDPy+B specimens revealed that the AgK clay exhibited larger iodide removal; further while the iodide removal by AgK specimen was almost instantaneous (complete in < 5 min), iodide removal by HDPy+B specimen was a slow process (18-24 h is needed to attain equilibrium). Likewise, the iodide retention capacity of the 50%B-50%HDPy+B mix (B = bentonite) is substantially smaller than of the 90%B-10%AgK and 80%B¬20%AgK mixes. Cation exchange capacity (CEC) measurements brought out that mixing AgK with bentonite besides imparting an iodide retention capacity essentially retains the large cation exchange capacity of the expansive clay. On the other hand mixing HDPy+B with bentonite imparts a smaller iodide retention capacity to the mix and leads to a notable reduction in the CEC of the expansive clay. Results of oedometer swell tests brought out that dilution of bentonite with 10% and 20% AgK specimen does not impact its swell potential and leads to some (10%) reduction in swell pressure, while dilution with 50% HDPy+B clay leads to notable (58%) reduction in swell potential and swell pressure (21%) underlining the superiority of AgK specimen as additive to bentonite in deep geological repositories. The swell pressure of the compacted 50%B-50%HDPy+B mix is 21% lower than that of the compacted bentonite specimen. Comparatively, dilution of bentonite with 10% and 20% AgK specimen induces 8-10% lower swell pressure in comparison to the undiluted counterpart. Swell pressure results of compacted 80%B-20%HDPy+B mix is not considered as this mix was unable to retain iodide ions. Superposing the field 129I concentration levels on I removal efficiency indicate that use of 90%B-10%AgK mix would suffice to provide 100% iodide removal efficiency and ensure that the swelling characteristics of bentonite is least affected by dilution.
9

Modélisation numérique du comportement des ouvrages souterrains par une approche viscoplastique / Numerical modeling of underground openings behavior with a viscoplastic approach

Kleine, Alexandra 14 November 2007 (has links)
La nature est complexe et c’est en toute modestie que les ingénieurs doivent chercher à prédire le comportement des ouvrages dans le sous-sol. La réalisation de projets industriels dans le domaine souterrain, à forts enjeux économiques et sociaux (traversées alpines, stockage de déchets nucléaires), nécessite d’évoluer vers une meilleure compréhension des mécanismes comportementaux des ouvrages à concevoir. Cette amélioration passe par une meilleure représentativité physique des mécanismes macroscopiques et par la mise à disposition d’outils de prédiction adaptés aux attentes et aux besoins des ingénieurs. Les outils de calculs développés dans ce travail s’inscrivent dans cette volonté de rapprocher les attentes de l’industrie et les connaissances liées à la rhéologie des géomatériaux. Ces développements ont ainsi débouché sur la proposition d’un modèle de comportement mécanique, adapté aux roches peu fissurées et assimilables à des milieux continus, intégrant, en particulier, l’effet du temps. Fil conducteur de cette étude, la problématique du sujet de thèse concerne précisément la prise en compte du comportement différé des massifs rocheux dans les modélisations et ses conséquences sur les ouvrages souterrains.Fondé sur des concepts physiques de référence, définis à différentes échelles (macro/méso/micro), le modèle rhéologique développé est transcrit dans un formalisme mathématique dans le but d’être mis en oeuvre numériquement.Les applications numériques proposées s’inscrivent principalement dans le contexte du stockage des déchets radioactifs. Elles concernent deux configurations d’ouvrages rigoureusement différentes : l’excavation du laboratoire souterrain canadien de l’AECL, dans le granite du Lac du Bonnet et le creusement de la galerie GMR du laboratoire de Bure (Meuse/Haute-Marne) dans l’argilite de l’Est. Dans les deux cas, l’utilisation du modèle a permis de mettre en évidence l’apport de la prise en compte du comportement différé sur la représentativité des prédictions numériques du comportement à court, moyen et long termes des ouvrages souterrains / Nature is complex and must be approached in total modesty by engineers seeking to predict the behavior of underground openings. The engineering of industrial projects in underground situations, with high economic and social stakes (Alpine mountain crossings, nuclear waste repository), mean striving to gain better understanding of the behavioral mechanisms of the openings to be designed. This improvement necessarily involves better physical representativeness of macroscopic mechanisms and the provision of prediction tools suited to the expectations and needs of the engineers. The calculation tools developed in this work is in step with this concern for satisfying industrial needs and developing knowledges related to the rheology of geomaterials. These developments led to the proposing of a mechanical constitutive model, suited to lightly fissured rocks, comparable to continuous media, while integrating more particularly the effect of time.Thread of this study, the problematics ensued from the subject of the thesis is precisely about the rock mass delayed behavior in numerical modeling and its consequences on underground openings design.Based on physical concepts of reference, defined in several scales (macro/meso/micro), the developed constitutive model is translated in a mathematical formalism in order to be numerically implemented.Numerical applications presented as illustrations fall mainly within the framework of nuclear waste repository problems. They concern two very different configurations of underground openings: the AECL’s underground canadian laboratory, excavated in the Lac du Bonnet granite, and the GMR gallery of Bure’s laboratory (Meuse/Haute-Marne), dug in argillaceous rock.In this two cases, this constitutive model use highlights the gains to be obtained from allowing for delayed behavior regarding the accuracy of numerical tunnel behavior predictions in the short, medium and long terms
10

The sorption of uranium(VI) and neptunium(V) onto surfaces of selected metal oxides and alumosilicates studied by in situ vibrational spectroscopy

Müller, Katharina 16 February 2010 (has links)
The migration behavior of actinides and other radioactive contaminants in the environment is controlled by prominent molecular phenomena such as hydrolysis and complexation reactions in aqueous solutions as well as the diffusion and sorption onto minerals present along groundwater flow paths. These reactions significantly influence the mobility and bioavailability of the metal ions in the environment, in particular at liquid-solid interfaces. Hence, for the assessment of migration processes the knowledge of the mechanisms occurring at interfaces is crucial. The required structural information can be obtained using various spectroscopic techniques. In the present study, the speciation of uranium(VI) and neptunium(V) at environmentally relevant mineral – water interfaces of oxides of titania, alumina, silica, zinc, and alumosilicates has been investigated by the application of attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy. Moreover, the distribution of the hydrolysis products in micromolar aqueous solutions of U(VI) and Np(V/VI) at ambient atmosphere has been characterized for the first time, by a combination of ATR FT-IR spectroscopy, near infrared (NIR) absorption spectroscopy, and speciation modeling applying updated thermodynamic databases. From the infrared spectra, a significant change of the U(VI) speciation is derived upon lowering the U(VI) concentration from the milli- to the micromolar range, strongly suggesting the dominance of monomeric U(VI) hydrolysis products in the micromolar solutions. In contradiction to the predicted speciation, monomeric hydroxo species are already present at pH ≥ 2.5 and become dominant at pH 3. At higher pH levels (> 6), a complex speciation is evidenced including carbonate containing complexes. For the first time, spectroscopic results of Np(VI) hydrolysis reactions are provided in the submillimolar concentration range and at pH values up to 5.3, and they are comparatively discussed with U(VI). For both actinides, the formation of similar species is suggested at pH ≤ 4, whereas at higher pH, the infrared spectra evidence structurally different species. At pH 5, the formation of a carbonate-containing dimeric complex, that is (NpO2)2CO3(OH)3−, is strongly suggested, whereas carbonate complexation occurs only under more alkaline conditions in the U(VI) system. The results from the experiments of the sorption processes clearly demonstrate the formation of stable U(VI) surface complexes at all investigated mineral phases. This includes several metal oxides, namely TiO2, Al2O3, and SiO2, serving as model systems for the elucidation of more complex mineral systems, and several alumosilicates, such as kaolinite, muscovite and biotite. From a multiplicity of in situ experiments, the impact of sorbent characteristics and variations in the aqueous U(VI) system on the sorption processes was considered. A preferential formation of an inner-sphere complex is derived from the spectra of the TiO2 and SiO2 phases. In addition, since the in situ FT-IR experiments provide an online monitoring of the absorption changes of the sorption processes, the course of the formation of the U(VI) surface complexes can be observed spectroscopically. It is shown that after prolonged sorption time on TiO2, resulting in a highly covered surface, outer-sphere complexation predominates the sorption processes. The prevailing crystallographic modification, namely anatase and rutile, does not significantly contribute to the spectra, whereas surface specific parameters, e.g. surface area or porosity are important. A significant different surface complexation is observed for Al2O3. The formation of inner-spheric species is assumed at low U(VI) surface coverage which is fostered at low pH, high ionic strength and short contact times. At proceeded sorption the surface complexation changes. From the spectra, an outer-spheric coordination followed by surface precipitation or polymerization is deduced. Moreover, in contrast to TiO2, the appearance of ternary U(VI) carbonate complexes on the γ-Al2O3 surface is suggested. The first results of the surface reactions on more complex, naturally occurring minerals (kaolinite, muscovite and biotite) show the formation of U(VI) inner-sphere sorption complexes. These findings are supported by the spectral information of the metal oxide surfaces. In this work, first spectroscopic results from sorption of aqueous Np(V) on solid mineral phases are provided. It is shown that stable inner-sphere surface species of NpO2+ are formed on TiO2. Outer-sphere complexation is found to play a minor role due to the pH independence of the sorption species throughout the pH range 4 – 7.6. The comparative spectroscopic experiments of Np(V) sorption onto TiO2, SiO2, and ZnO indicate structurally similar bidentate surface complexes. The multiplicity of IR spectroscopic experiments carried out within this study yields a profound collection of spectroscopic data which will be used as references for future investigations of more complex sorption systems in aqueous solution. Furthermore, from a methodological point of view, this study comprehensively extends the application of ATR FT-IR spectroscopic experiments to a wide range in the field of radioecology. The results obtained in this work contribute to a better understanding of the geochemical interactions of actinides, in particular U(VI) and Np(V/VI), in the environment. Consequently, more reliable predictions of actinides migration which are essential for the safety assessment of nuclear waste repositories can be performed. / Das Migrationsverhalten von Aktiniden und anderen radioaktiven Schadstoffen in der Umwelt wird von wichtigen molekularen Prozessen entlang der Grundwasserfließwege reguliert. Dazu gehören sowohl die Hydrolyse und Komplexierung in wässrigen Lösungen als auch Diffusion und Sorption der Schwermetalle an Mineralen. Diese Reaktionen beeinflussen entscheidend die Mobilität und Bioverfügbarkeit der Metallionen in der Umwelt, insbesondere an den fest-flüssig Grenzflächen. Genaue Kenntnisse über die an diesen Grenzflächen stattfindenden Mechanismen sind somit entscheidend, um Migrationsprozesse verlässlich abschätzen zu können. Die benötigten strukturellen Informationen können mit verschiedenen spektroskopischen Techniken ermittelt werden. Das Ziel der vorliegenden Arbeit war die Untersuchung der Speziation von Uran(VI) und Neptunium(V) an umweltrelevanten Grenzflächen von Oxiden des Titans, Aluminiums, Siliziums und Zinks und von Alumosilikaten mittels ATR FT-IR Spektroskopie. Des Weiteren wurde die Verteilung aquatischer Spezies in mikromolaren Lösungen des U(VI) und Np(V/VI) unter Normalbedingungen charakterisiert. Diese erstmalige Untersuchung wurde mit einer Kombination aus Speziationsmodellierung unter Anwendung aktueller thermodynamischer Daten und ATR FT-IR und NIR Absorptionsspektroskopie realisiert. Die Infrarotspektren zeigen eine deutliche Änderung der Speziesverteilung im Konzentrationsverlauf vom millimolaren zum mikromolaren Bereich. Dies verweist auf die Bildung monomerer U(VI) Hydrolyseprodukte. Im Gegensatz zu berechneten Speziationen werden diese monomeren Komplexe schon bei pH ≥ 2,5 gebildet und dominieren die Speziation bei pH 3. Bei höheren pH-Werten (> 6) konnte eine komplexe Speziesverteilung mit Anteilen von Karbonatkomplexen nachgewiesen werden. Erstmals konnten im Rahmen dieser Arbeit spektroskopische Befunde der Hydrolysereaktionen des Np(VI) im submillimolaren Konzentrationsbereich bis pH 5,3 erhalten werden. Diese wurden im Vergleich mit der U(VI) Speziation diskutiert. Obwohl im sauren Bereich (pH ≤ 4) die Bildung ähnlicher Komplexe nachgewiesen wurde, zeigen die bei höheren pH-Werten erhaltenen Spektren eine unterschiedliche Speziesverteilung. Im Gegensatz zum U(VI) bildet das Np(VI) schon bei pH 5 karbonathaltige aquatische Spezies wie (NpO2)2CO3(OH)3−. Die Ergebnisse der Sorptionsexperimente von U(VI) zeigen die Bildung stabiler Oberflächenkomplexe an allen untersuchten Mineralphasen. Dies umfasst mehrere als Modellsystem dienende Metalloxide wie TiO2, Al2O3 und SiO2, als auch komplexere Alumosilikate wie Kaolinit, Muskovit und Biotit. Für eine detaillierte Charakterisierung der Oberflächenkomplexe wurde eine Vielzahl von in situ Sorptionsexperimenten durchgeführt, die den Einfluss unterschiedlicher Parameter der mineralischen Phase als auch des wässrigen U(VI) Systems berücksichtigen. Die bevorzugte Bildung von innersphärischen Komplexen an TiO2 und SiO2 wird aus den spektroskopischen Daten abgeleitet. Da die in situ FT-IR Spektroskopie eine kontinuierliche Registrierung der Absorptionsänderungen während der ablaufenden Sorptionsprozesse erlaubt, kann somit der Verlauf dieser Prozesse quasi in Echtzeit spektroskopisch verfolgt werden. Es konnte gezeigt werden, dass mit fortschreitender Sorptionsdauer, d.h. bei hohen Beladungsdichten, die Bildung einer weiteren außersphärischen Spezies die Sorption dominert. Die vorliegende kristallographische Modifikation, Anatas und Rutil, ist nicht maßgeblich für das Auftreten unterschiedlicher Sorptionsprozesse verantwortlich, obwohl Parameter wie die spezifische Oberfläche und die Porosität für den Sorptionsprozess von Bedeutung sind. Deutlich verschiedene Oberflächenreaktionen werden für Al2O3 beobachtet. Aus den Spektren kann die Ausbildung einer innersphärischen Spezies bei sehr niedrigen U(VI) Beladungen, niedrigen pH-Werten, hohen Ionenstärken und kurzen Kontaktzeiten abgeleitet werden. Bei fortschreitender Sorption ändert sich die Art der Oberflächenkomplexe. Zunächst bilden sich außersphärische Spezies, während im weiteren Verlauf die Spektren auf eine beginnende Oberflächenausfällung bzw. Polymerisation hinweisen. Weiterhin wird das Auftreten von ternären U(VI) Karbonatkomplexen an γ-Al2O3 aus den spektroskopischen Daten abgeleitet. Die ersten Ergebnisse der Sorptionsexperimente an komplexeren, natürlich auftretenden Mineralphasen (Kaolinit, Muskovit und Biotit) zeigen eine bevorzugte Ausbildung von innersphärischen U(VI) Komplexen. Diese Resultate werden durch die spektralen Befunde der Experimente der Metalloxide gestützt. Erstmalig werden in dieser Arbeit spektroskopische Ergebnisse der Sorptionsprozesse von wässrigen Np(V) an verschiedenen Mineralphasen präsentiert. Wie U(VI) bildet Np(V) stabile innersphärische Oberflächenkomplexe an TiO2. Die Speziesverteilung an der TiO2 Oberfläche ist im pH Bereich 4 – 7,6 konstant. Daher ist zu erwarten, dass eine außersphärische Komplexierung hier nur eine untergeordnete Rolle spielt. Der Vergleich von Spektren der Np(V) Sorptionskomplexe an TiO2, SiO2 und ZnO weist auf die Bildung strukturell ähnlicher bidentater Komplexe hin. Die Vielzahl der hier vorgestellten infrarotspektroskopischen Experimente bietet eine fundierte Sammlung spektroskopischer Daten, die für zukünftige Untersuchungen komplexer aquatischer und mineralischer Systeme unerlässlich ist. Gleichzeitig wurde der Anwendungsbereich der ATR FT-IR Technik auf dem Gebiet der Radioökologie umfassend erweitert. Die im Rahmen dieser Arbeit gewonnenen Ergebnisse tragen zu einem besseren Verständnis der geochemischen Wechselwirkungen von Aktiniden, im Speziellen von U(VI) und Np(V) in der Umwelt bei. Damit unterstützen sie den Aufklärungsprozess der Migration von radioaktiven Kontaminationen und dienen als Grundlage für zuverlässige Prognosen für die Sicherheitsbewertung von Endlagern für nukleare Abfälle.

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