High-level radioactive waste (HLW) poses threat to the biosphere. Geological disposal is accepted as a safe way for HLW disposal. Waste canisters made of Sintered Silicon Carbide (SSiC) are proposed and geomechanical safety aspects relating to such SSiC canisters are investigated. First part of the thesis reviews the state-of-the-art and demands for HLW disposal. The reason for considering Silicon Carbide (SiC) as canister material is explained. Especially in terms of corrosion and lifetime, ceramics and especially SiC is superior to metals or concrete. The only concern is its brittle behavior. The second part of the thesis presents results on static and dynamic mechanical properties of SiC in general and in particular for SSiC based on literature review and own lab tests. Although strength values for SiC and especially SSiC are very high, the extreme brittle behavior has to be considered in case of impact or point-like loading. The third and most extensive part of the thesis part contains numerical simulations, which consider most critical potential loading situations during transport and installation of the canisters underground. Both, pure elastic continuum and DEM based models are used considering the following loading situations (critical scenarios): Freefall of canister during transport or installation (FF), Impact by falling rock block at disposal site (RF), Point loading due to accidental insertion of small stone below the canister (PL), Anisotropic earth pressure loading after disposal (EP). Coating to protect the canisters against damage is investigated and preliminary parameters in terms of stiffness and thickness are recommended.

Altered flows that are low-MgO chemical types of the Grande Ronde Basalt crop out in the steep walls of the Grande Ronde River canyon near Troy, Wallowa County, Oregon. The alteration effects in these flows are being investigated as a natural analog system to a high level nuclear waste repository in basalt. The flows within the study are referred to as the analog flow, in which the alteration effects are the strongest, and the superjacent flow. The analog flow crops out at Grande Ronde River level and a roadcut-outcrop is developed in the flow-top breccia of this flow. The two flows have been divided into flow zones based on intraflow structures observed in the field and primary igneous textures observed in thin section. These zones include, from the base upward, the flow interior, transition, and flow-top breccia zones of the analog flow, the interflow contact zone, and the flow interior and flow-top breccia zone of the superjacent flow. The intraflow structures and textures of the transition and interflow contact zones are atypical of Grande Ronde Basalt flows. The transition zone is transitional in textures between the flow interior zone and flow-top breccia zone, and includes holocrystalline spines mantled with fused in situ breccias. The interflow contact zone reflects the dynamic interaction during the emplacement of the superjacent flow manifested as invasive basalt tongues, clasts shed from tongues, pipe vesicles and tree molds, and pockets of breccia caught up in the base of the superjacent flow.

Die Bildung und Beständigkeit von CSH-Phasen wurde in Abhängigkeit von Zeit, Ca/Si-Verhältnis, Temperatur, SiO2-Reaktivität, w/s-Verhältnis und NaCl-Sättigung der Lösung untersucht. Semikristalline CSH-Phasen bilden tobermoritähnliche Schichtstrukturen aus und weisen trotz ihrer Metastabilität hohe Beständigkeit bei 25 °C auf. Durch Erhöhung von Temperatur und w/s-Verhältnis wird deren Umwandlung zu kristallinen CSH-Phasen begünstigt, während NaCl-Sättigung der wässrigen Lösung die Kristallisation hemmt. Die Löslichkeit von CSH-Phasen ändert sich ebenfalls durch Variation von Temperatur und NaCl-Konzentration. Die NaCl-Sättigung führt in Folge der teilweisen Substitution von Ca2+ durch Na+ in den Festphasen zu einer deutlichen Erhöhung der Ca2+-Konzentrationen in Lösung. Mischphasenmodelle beschreiben dieses Verhalten in Berechnungen zumeist nicht hinreichend. Die Erweiterung der Datenbasis und Anpassungen der Modelle sind nötig. Mg2+-haltige Kontaktlösungen führen zur Auflösung von CSH- unter Bildung von MSH-Phasen.

本論文以台灣「低放選址政策」的信任問題為主題，採用文獻研究、調查訪談、焦點座談、問卷調查等多元研究方法，一方面參照並補充TCC模型作為理論架構，分析「信任」如何分別透過其知識與非知識屬性，影響台東與金門兩縣民眾的最終處置場設施接受度，藉以充實對公共政策中不行動面向之理解，並增加對非科學理性因素之重視。另方面，則綜合實證分析結果，並參酌近期國/內外選址的風險溝通經驗，探討「低放選址政策」如何納入重建信任的風險溝通模式，以協調科學與民主、專家與民眾在決策過程中的關係。研究結果指出，「低放選址政策」的信任問題，彰顯了過去人們用以確保政府機關不負所託的科學理性及專家決策模式，在現代風險社會中，不再足以讓民眾繼續作出授予信任的判斷，並在風險議題中合作。有鑑於在信任的分類與運作模式中，受價值相似性啟發的信任，主導了對科學證據與信心的詮釋。因此，對風險議題進行社會選擇的決策模式，必須能夠重塑集體的價值相似性，形成新的信任穩定機制。本論文乃建議一個重視「代表性、共同框架、決策影響力」的參與式對話平台，將可藉由政策審議架構，尋求在共享價值下，可被普遍接受的正義原則及解決之道，以提升「低放選址政策」的接受度與正當性。 / In this study, the author focused on the trust problems related to the “low radioactive waste disposal site selection” topic and adopted the literature review, survey interview, focus group, and questionnaire survey study methods. One of the objectives was to reference and supplement the TCC model as the theoretical framework to analyze how “trust” as well as its knowledge and non-knowledge attributes can affect acceptance for the final disposal site by the people of Taitung and Kinmen in order to enrich our understanding of the inaction in public policies and strengthen the emphasis on non-scientific rationality factors. The other objective was to incorporate the analysis and empirical results, reference the recent domestic/foreign disposal site selection risk communication experiences, and explore how to incorporate a trust rebuilding risk-communication method into the low radioactive waste disposal site selection, in order to coordinate the relationships between science and democracy as well as the experts and citizens throughout the policy-making process. The trust problems related to low radioactive waste disposal site selection discussed in this study highlight the fact that the scientific rationality and expert policy-making mode relied upon by the government agencies are no longer sufficient for the people to trust the government’s judgments or cooperate in the risk topics during the modern risk society. In terms of TCC model, trust inspired by value similarities drives the interpretation of scientific evidence and confidence. Therefore, the policy-making process that enable to risk-topic related social choice must be able to reshape the shared value and form a new trust stabilization mechanism. In this study, the author proposed a participative discourse platform that emphasizes on “representation, collaborative framing, and decision impacts” may adopt the framework for policy deliberation in search of shared values, as well as generally accepted justice principles and solutions, in order to enhance the acceptance and legitimacy for the low radioactive waste disposal site selection.

Although products of coal combustion (PCCs) such as coal ash are currently exempted from classification as a hazardous waste in the United States under the 1976 Resource Conservation and Recovery Act (RCRA), the U.S. Environmental Protection Agency (EPA) is now revising a proposed rule to modify disposal practices for these materials in order to prevent contamination of ground- and surface water sources by leached trace elements. This paper analyzes several aspects of EPA’s scientific reasoning for instating the rule, with the intent of answering the following questions: 1) Are EPA’s cited values for PCC production and disposal accurate estimates of annual totals?; 2) In what ways can EPA’s leaching risk modeling assessment be improved?; 3) What is the total quantity of trace elements contained within all PCCs disposed annually?; and 4) What would be the potential costs and feasibility of reclassifying PCCs not under RCRA, but under existing NRC regulations as low-level radioactive waste (LLRW)? Among the results of my calculations, I found that although EPA estimates for annual PCC disposal are 20% larger than industry statistics, these latter values appear to be closer to reality. Second, EPA appears to have significantly underestimated historical PCC disposal: my projections indicate that EPA’s maximum estimate for the quantity of fly ash landfilled within the past 90 years was likely met by production in the last 30 years alone, if not less. Finally, my analysis indicates that while PCCs may potentially meet the criteria for reclassification as low-level radioactive waste by NRC, the cost of such regulation would be many times that of the EPA June proposed disposal rule ($220-302 billion for PCCs disposed in 2008 alone, versus $1.47 billion per year for the Subtitle C option and $236-587 million for Subtitle D regulatory options). / text

The aim of this doctoral dissertation is to assess the probable impact of ionizing radiation on the public health and the environment (including fauna and flora) in the vicinity of nuclear power engineering objects (in case of the Maišiagala near-surface radioactive waste repository – by evaluating the possible impact on the human health, while in case of the Ignalina NPP cooling basin, Lake Drūkšiai – by evaluating the possible impact on the freshwater ecosystem biota) by applying probabilistic methods as well as to determine whether this activity after assessment of its character and impact on the environment meets the standards valid in the Republic of Lithuania or in the European Union and is permissible at a selected site at present or in the future. In the work two main programs, RESRAD-OFFSITE and ERICA, using scattering of site-specific parameter values and probabilistic (correlation, regressive, sensitivity, etc.) analysis, have been applied. It has been determined that in the environment of the Maišiagala repository after installation of additional protective barriers the annual effective human exposure dose is significantly lower as compared to the limited dose and 95th percentile dose not exceed the exposure of 1 mSv per year regulated in the hygiene standards. The exposure dose rate of standardized organisms of Lake Drūkšiai, the Ignalina NPP cooler, freshwater ecosystem biota due to the INPP discharges and waterway radionuclide migration from a hypothetic... [to full text] / Šios daktaro disertacijos tikslas - įvertinti galimą jonizuojančiosios spinduliuotės poveikį visuomenės sveikatai ir aplinkai (tame tarpe gyvūnijai ir augalijai) branduolinės energetikos objektų aplinkoje (Maišiagalos radioaktyviųjų atliekų saugyklos atveju - vertinant galimą poveikį žmogui, ir IAE aušintuvo Drūkšių ežero atveju - vertinant galimą poveikį gėlavandenės ekosistemos biotai), taikant tikimybinius metodus; nustatyti, ar ši veikla, įvertinus jos pobūdi ir poveikį aplinkai, atitinka Lietuvos Respublikoje arba Europos Sąjungoje galiojančius standartus, yra leistina pasirinktoje vietoje dabartiniu laikotarpiu arba ateityje. Darbe buvo taikomos 2 pagrindinės programos: RESRAD-OFFSITE ir ERICA., naudojant vietines sąlygas atitinkančius parametrų verčių išbarstymą, taikant tikimybinę (koreliacinę, regresinę, jautrio ir kt.) analizę. Nustatyta, kad, įrengus papildomus apsauginius barjerus, Maišiagalos saugyklos aplinkoje metinė efektinė gyventojų apšvitos dozė yra ženkliai mažesnė lyginant su apribotosios dozės dydžiu, 95 procentilė nesiekia higienos normose patvirtintos 1mSv per metus ribinės dozės dydžio. Ignalinos AE aušintuvo Drūkšių ežero gėlavandenės ekosistemos biotos standartizuotųjų organizmų apšvitos dozės galia dėl IAE nuotekų ir radionuklidų sklaidos vandens keliu iš hipotetinio Stabatiškės radioaktyviųjų atliekų kapinyno rodo, kad apšvitos dozės galia dėl antropogeninės kilmės radionuklidų jonizuojančiosios spinduliuotės poveikio neviršija Europos Sąjungoje... [toliau žr. visą tekstą]

Šios daktaro disertacijos tikslas - įvertinti galimą jonizuojančiosios spinduliuotės poveikį visuomenės sveikatai ir aplinkai (tame tarpe gyvūnijai ir augalijai) branduolinės energetikos objektų aplinkoje (Maišiagalos radioaktyviųjų atliekų saugyklos atveju - vertinant galimą poveikį žmogui, ir IAE aušintuvo Drūkšių ežero atveju - vertinant galimą poveikį gėlavandenės ekosistemos biotai), taikant tikimybinius metodus; nustatyti, ar ši veikla, įvertinus jos pobūdi ir poveikį aplinkai, atitinka Lietuvos Respublikoje arba Europos Sąjungoje galiojančius standartus, yra leistina pasirinktoje vietoje dabartiniu laikotarpiu arba ateityje. Darbe buvo taikomos 2 pagrindinės programos: RESRAD-OFFSITE ir ERICA., naudojant vietines sąlygas atitinkančius parametrų verčių išbarstymą, taikant tikimybinę (koreliacinę, regresinę, jautrio ir kt.) analizę. Nustatyta, kad, įrengus papildomus apsauginius barjerus, Maišiagalos saugyklos aplinkoje metinė efektinė gyventojų apšvitos dozė yra ženkliai mažesnė lyginant su apribotosios dozės dydžiu, 95 procentilė nesiekia higienos normose patvirtintos 1mSv per metus ribinės dozės dydžio. Ignalinos AE aušintuvo Drūkšių ežero gėlavandenės ekosistemos biotos standartizuotųjų organizmų apšvitos dozės galia dėl IAE nuotekų ir radionuklidų sklaidos vandens keliu iš hipotetinio Stabatiškės radioaktyviųjų atliekų kapinyno rodo, kad apšvitos dozės galia dėl antropogeninės kilmės radionuklidų jonizuojančiosios spinduliuotės poveikio neviršija Europos Sąjungoje... [toliau žr. visą tekstą] / The aim of this doctoral dissertation is to assess the probable impact of ionizing radiation on the public health and the environment (including fauna and flora) in the vicinity of nuclear power engineering objects (in case of the Maišiagala near-surface radioactive waste repository – by evaluating the possible impact on the human health, while in case of the Ignalina NPP cooling basin, Lake Drūkšiai – by evaluating the possible impact on the freshwater ecosystem biota) by applying probabilistic methods as well as to determine whether this activity after assessment of its character and impact on the environment meets the standards valid in the Republic of Lithuania or in the European Union and is permissible at a selected site at present or in the future. In the work two main programs, RESRAD-OFFSITE and ERICA, using scattering of site-specific parameter values and probabilistic (correlation, regressive, sensitivity, etc.) analysis, have been applied. It has been determined that in the environment of the Maišiagala repository after installation of additional protective barriers the annual effective human exposure dose is significantly lower as compared to the limited dose and 95th percentile dose not exceed the exposure of 1 mSv per year regulated in the hygiene standards. The exposure dose rate of standardized organisms of Lake Drūkšiai, the Ignalina NPP cooler, freshwater ecosystem biota due to the INPP discharges and waterway radionuclide migration from a hypothetic... [to full text]

This study examines the relationship between atomic energy production and community identity in Richland, Washington. Over the past fifty years, the identity of southeastern Washington has been intimately tied to production and industry at the Hanford Site. Today, however, environmental restoration and waste management programs have replaced plutonium production. The decline of the nuclear industry has influenced reinterpretations of local history and community identity through public display, commodity goods, and the re-scripting of historical texts. / Department of Anthropology

Les activités nucléaires génèrent des déchets radioactifs classés selon leur niveau d’activité et la durée de vie des radioéléments présents. La garantie d’un classement et d’une gestion optimale nécessite une caractérisation précise. Les déchets de moyenne et haute activité, contenant des radioéléments à vie très longue, seront stockés en profondeur pendant plusieurs centaines de milliers d’années, à l’issue desquelles il est nécessaire de pouvoir garantir l’absence de risques pour l’homme et l’environnement, non seulement sur le plan radiologique, mais aussi en ce qui concerne des éléments stables, toxiques du point de vue chimique. Cette thèse concerne la caractérisation par activation neutronique de ces éléments toxiques, ainsi que celle des matières nucléaires présentes dans les colis. Elle a été réalisée dans le cadre d’une collaboration entre le Laboratoire de Mesures Nucléaires du CEA Cadarache, en France, et l’institut de Gestion des Déchets Radioactifs et de Sûreté des Réacteurs du centre de recherche FZJ (Forschungszentrum Jülich), en Allemagne. La première étude a consisté à valider le modèle numérique de la cellule d’activation neutronique MEDINA (FZJ) avec le code de transport Monte Carlo MCNP. Les rayonnements gamma prompts de capture radiative d’échantillons contenant des éléments d’intérêt (béryllium, aluminium, chlore, cuivre, sélénium, strontium et tantale) ont été mesurés et comparés aux simulations avec diverses bases de données nucléaires, permettant d’aboutir à un accord satisfaisant et validant le schéma de calcul en vue des études suivantes. Ensuite, la mesure des rayonnements gamma retardés de fissions induites sur les isotopes 235U et 239Pu a été étudiée pour des fûts de 225 L contenant des enrobés bitumineux ou une matrice béton, représentatifs de déchets produits en France et en Allemagne. Les rendements d’émission des rayonnements gamma retardés de fission d’intérêt, cohérents avec ceux publiés dans la littérature, ont été déterminés à partir des mesures d’échantillons métalliques d’uranium et de plutonium dans la cellule d’activation neutronique REGAIN du LMN. Le signal utile a ensuite été extrapolé par simulation MCNP pour une répartition homogène d’isotopes 239Pu ou 235U dans les matrices considérées, en utilisant le modèle numérique de MEDINA. Des signaux faibles, de l’ordre de 100 coups par gramme d’isotope 239Pu ou 235U, ont été obtenus. Pour le colis d’enrobés bitumineux, le niveau d’irradiation gamma très élevé, dû à une activité en 137Cs de l’ordre de 1 TBq par fût, nécessiterait l’utilisation d’une collimation et/ou d’écrans pour éviter la saturation de l’électronique de mesure, rendant indétectables les rayonnements gamma retardés de fission. Les colis de déchets bétonnés produits en Allemagne présentant un niveau d’activité plus faible, il a été possible d’estimer des limites de détection allant de 10 à 290 g d’isotope fissile 235U ou 239Pu, selon la raie gamma considérée, suite à la mesure du bruit de fond actif dans MEDINA avec une matrice béton maquette. Afin d’améliorer ces performances, le blindage du détecteur germanium de MEDINA a été optimisé à l’aide de simulations MCNP, montrant la possibilité de réduire les bruits de fond gamma et neutron d’un facteur 4 et 5, respectivement. La validation expérimentale de l’efficacité du blindage a été effectuée à partir de configuration simples à implémenter dans MEDINA, confirmant les facteurs de réduction attendus. Un blindage du détecteur optimal permettrait d’améliorer les limites de détection et aussi d’utiliser une source de neutrons d’intensité supérieure, comme un générateur de neutron à haut flux ou un accélérateur linéaire d’électrons avec une cible de conversion appropriée. / Nuclear activities produce radioactive wastes classified following their radioactive level and decay time. An accurate characterization is necessary for efficient classification and management. Medium and high level wastes containing long lived radioactive isotopes will be stored in deep geological storage for hundreds of thousands years. At the end of this period, it is essential to ensure that the wastes do not represent any risk for humans and environment, not only from radioactive point of view, but also from stable toxic chemicals. This PhD thesis concerns the characterization of toxic chemicals and nuclear material in radioactive waste, by using neutron activation analysis, in the frame of collaboration between the Nuclear Measurement Laboratory of CEA Cadarache, France, and the Institute of Nuclear Waste Management and Reactor Safety of the research center, FZJ (Forschungszentrum Jülich GmbH), Germany. The first study is about the validation of the numerical model of the neutron activation cell MEDINA (FZJ), using MCNP Monte Carlo transport code. Simulations and measurements of prompt capture gamma rays from small samples measured in MEDINA have been compared for a number of elements of interest (beryllium, aluminum, chlorine, copper, selenium, strontium, and tantalum). The comparison was performed using different nuclear databases, resulting in satisfactory agreement and validating simulation in view of following studies. Then, the feasibility of fission delayed gamma-ray measurements of 239Pu and 235U in 225 L waste drums has been studied, considering bituminized or concrete matrixes representative of wastes produced in France and Germany. The delayed gamma emission yields were first determined from uranium and plutonium metallic samples measurements in REGAIN, the neutron activation cell of LMN, showing satisfactory consistency with published data. The useful delayed gamma signals of 239Pu and 235U, homogeneously distributed in the 225 L matrixes, were then determined by MCNP simulations using MEDINA numerical model. Weak signals of about one hundred counts per gram of 239Pu or 235U after 7200 s irradiation were obtained. Because of the high gamma emission in the bituminized waste produced in France (about 1 TBq of 137Cs per drum), the use of collimator and/or shielding is mandatory to avoid electronic saturation, making fission delayed gamma rays undetectable. However, German concrete drums being of lower activity, their corresponding active background was measured in MEDINA with a concrete mock-up, leading to detection limits between 10 and 290 g of 235U or239Pu, depending on the delayed gamma line. In order to improve these performances, the shielding of MEDINA germanium detector was optimized using MCNP calculations, resulting in gamma and neutron background reduction factors of 4 and 5, respectively. The experimental validation of the shielding efficiency was performed by implementing easy-to-build configurations in MEDINA, which confirmed the expected background reduction factors predicted by MCNP. Thanks to an optimized detector shielding, it will also be possible to use a higher neutron emission source, like a high flux neutron generator or an electron LINAC with appropriate conversion targets, in view to further reduce detection limits.

The chemistry of actinides in solution is a very important aspect of the nuclear fuel cycle, especially as the energy needs of the world continue to increase. However, the radio-active nature of the actinides makes experimentation very difficult and dedicated expensive instruments are required. In addition, the disposal of radio-active waste materials requires a proper understanding of their chemistry at a molecular level. To tackle the problem, and to underpin the experimental studies, in this thesis we have studied the redox chemistry and disproportionation mechanism of actinyl complexes in solution using state-of-the art computational methods. Reduction potentials of actinyl complexes in solution have been estimated in solution using density functional theory (DFT) approaches. Solvation effects were included in the quantum chemistry calculations with the conductor like polarisable continuum model (CPCM) solvation method. First of all, we have validated our computational method by studying a variety of solute cavity definitions within the CPCM solvation model and assessed the performance of a range of DFT functionals to suitable to accurately describe the actinide chemistry in solution. Penta-valent uranyl(V) ions are unstable and readily disproportionate; in this study we have explored outer-sphere electron transfer and disproportionation mechanisms to determine the stability of these ions in solution. We have found that the process of outer-sphere disproportionation is unlikely to occur in non-aqueous solutions, such as DMSO, DMF, DCM, acetonitrile and pyridine, when the uranyl(V) ion is bound with a multi-dentate organic ligand. However, our computational results hypothesise that the presence of a trace of water in the experimental conditions can promote a disproportionation reaction by protonating the uranyl(V) ‘yl’ oxygen atoms and then the electron transfer process would proceed through either inner or outer sphere mechanism. In addition, the effect of alkali metal cations on the outer-sphere disproportionation mechanisms was also studied. Overall it has been shown that DFT can be used to accurately predict the redox properties of actinyl complexes in solution and thus contributing for an effective and efficient design of nuclear material separations, proper as well as safer radioactive waste disposal.