Corrosion Related to the Nuclear Waste Containers

The disposal of nuclear waste is a demanding topic, and the existing methods, whether it is temporary storage in spent fuel pools or storage in geological repositories, both face the risk of corrosion-related problems. Any failure in these storage methods can potentially lead to the release of radioactive materials into the environment. To avert such catastrophic scenarios, people in the nuclear industry consistently monitor and maintain these storage facilities endlessly and attempt to improve the plans designed to store nuclear waste. Here, I will examine the nuclear waste management organization (NWMO) plan in Canada. Choosing an appropriate location for the construction of a deep geologic repository (DGR) for high-level nuclear waste is a challenging process that often generates social conflicts, and only a handful of countries have been able to navigate this process successfully, and Canada is currently on the brink of making such a decision

A Climatology of Northwest Missouri Snowfall Events: Long Term Trends and Interannual Variability.

The goal of this study was to develop a 50-year statistical climatology of snowfall occurrences using data from a dense network of cooperative station observations covering northwest and central Missouri, and these records were provided by the Missouri Climate Center. This included a study of the long term trends and interannual variability in snowfall occurrence as related to sea surface temperature variations in the Pacific Ocean basin associated with the El Nino and Southern Oscillation (ENSO) and the North Pacific Oscillation (NPO). These trends and variations were then related to four synoptic-scale flow regimes that produce these snowfalls in the Midwest. The results demonstrate that during the snowfall season (Oct - April) the northwest Missouri region can expect about eight snowfall events which produce three or more inches of accumulation. While no significant long-term trend in overall snowfall occurrence was found, a decrease in the number of extreme events (10 or more inches) was noted. Also, fewer snowfall events were found during El Nino years, while more heavy snowfall events occurred during "neutral" years, and these results could be related to synoptic- scale variability. A closer examination of the results demonstrated that El Nino/La Nina related variability in snowfall occurrence was superimposed on longer-term NPO-related variability.This research was supported by the University Corporation for Atmospheric Research (UCAR) Cooperative program for Operational Meteorological Education and Training (COMET) Outreach Programunder award # 98115921

Reasons Why Low-Income Women in Northwest Missouri Do Not Access No-Cost Mammography Services

Title from PDF of title page, viewed on December 8, 2010.Dissertation advisor: Maithe EnriquezVita.Includes bibliographic references (pages 82-105).Dissertations (Ph.D.)--School of Nursing. University of Missouri--Kansas City, 2010.Mammography is one of the best screening methods to detect early breast cancer, identify the cancer at a more treatable stage, expand treatment options, and reduce mortality. Despite access to no-cost mammography services, Missouri women experience the lowest mammography utilization rate in the nation. In Northwest Missouri the rate of mammography utilization is particularly low: 1 in 3 women over the age of 40 years have never had a mammogram. The purpose of this study was to identify factors that prevent uninsured, low-income women from Northwest Missouri from accessing no-cost mammography services. A narrative descriptive design was utilized to: 1) examine attitudes concerning mammography, 2) gain insight into perceived barriers and facilitators to mammography, 3) gain an understanding of factors influencing mammography behavior and 4) identify potential strategies to increase mammography access and utilization among uninsured, low-income women age 40 to 64 years in Northwest Missouri who have never had a mammogram. Participants in this study (n=12) were recruited from community agencies that provided social services to low-income families. Semi-structured individual interviews were conducted, guided by the Integrated Behavioral Model. Data were analyzed using content analysis to formulate narrative descriptions about attitudes, perceived norms, perceived control, and self-efficacy concerning mammography use. There were four themes that emerged from the data: Competing priorities, the costs of having a `free' mammogram, attitudes about mammography, and navigating the `red tape'. Findings indicated that the participants in this study experienced competing priorities and viewed screening behaviors, such as mammography, as a low priority. These women had conflicting attitudes about the advantages and disadvantages of mammography. Their perceptions about mammography were greatly influenced by family and friends. The overarching barrier to no-cost mammography for each of the participants was the amount of "red tape" encountered when navigating the healthcare system in order to obtain a "free" mammogram. Findings from this study may serve to inform future intervention strategies that may reduce barriers and increase utilization of no-cost mammography programs by eligible women.Abstract -- List of Illustrations -- List of Tables -- Acknowledgments -- Introduction -- Review of the Literature -- Methods -- Results -- Summary, Conclusions, Limitations, Recommendations and Implications for Practice -- Appendices -- References -- Vita

Comsol Modelling of Uniform Corrosion of Used Nuclear Fuel Canisters

Uniform corrosion of copper can occur in spent nuclear fuel canisters placed in deep geological repositories (DGR). To estimate the minimum thickness for safe design of canisters, it is necessary to analyze the corrosion rate. Copper Corrosion Model (CCM) has been used to model the corrosion process taking into account processes including adsorption/desorption, precipitation/dissolution, oxidation, and parameters including oxygen concentration, chloride, moisture and associated rate constants. In this work, CCM has been incorporated in COMSOL and validated with CCM. Once validated, the COMSOL model was used to examine the sensitivity of various parameters with respect to copper corrosion. It was found that initial chloride concentration, adsorption/desorption of cupric ions are parameters that most effect copper corrosion. The developed model can be used to simulate the uniform corrosion process under DGR conditions with more complexity including variation in temperature, saturation and pressure, and aid in the design of copper canisters

Design Optimization for Spatial Arrangement of Used Nuclear Fuel Containers

Canada's proposed deep geological repository is a multiple-barrier system designed to isolate used nuclear fuel containers (UFCs) indefinitely with no release of radionuclides for at least one million years. Placing UFCs together as densely as possible is ideal for mitigating repository size and cost. However, due to heat generation from radioactive decay and material limitations, a key design criterion is that the maximum temperature inside the repository must not exceed 100 °C. To satisfy that criterion, design optimization for the spatial arrangement of UFCs in a crystalline rock repository is performed. Spatial arrangement pertains to: (i) the spacing between UFCs, (ii) the separation between placement rooms underground, and (iii) the locations of variously aged UFCs that generate heat at different rates. Most studies have considered UFCs to be identical in age during placement into the repository. Parameter analyses have also been performed to evaluate repository performance under probable geological conditions. In this work, the various ages of UFCs and the uncertainties in spacing-related design variables are of focus. Techniques for the actual placement of UFCs in the deep geological repository based on their age and methods for repository risk analysis using yield optimization are developed. The thermal evolution inside the deep geological repository is simulated using a finite element model. With many components inside the massive repository planned for upwards of 95,000 UFCs, direct optimization of the model is impractical or even infeasible due to it being computationally expensive to evaluate. Surrogate optimization is used to overcome that burden by reducing the number of detailed evaluations required to reach the optimal designs. Two placement cases are studied: (i) UFCs all having been discharged from a Canadian Deuterium Uranium reactor for 30 years, which is a worst-case scenario, and (ii) UFCs having been discharged between 30 and 60 years. Design options that have UFC spacing 1–2 m and placement room separation 10–40 m are explored. The placement locations of the variously aged UFCs are specified using either sinusoidal (cosine) functions or Kumaraswamy probability density functions. Yield optimization under assumed design variable tolerances and distributions is performed to minimize the probability of a system failure, which occurs when the maximum temperature constraint of 100 °C is exceeded. This method allows variabilities from the manufacturing and construction of the repository components that affect the design variables to be taken into account, incorporating a stochastic aspect into the design optimization that surrogate optimization would not include. Several distributions for the design variables are surveyed, and these include uniform, normal, and skewed distributions—all of which are approximated by Kumaraswamy distributions

MICROBIAL ABUNDANCE, DIVERSITY, AND POTENTIAL ACTIVITY IN BENTONITE CLAY

The Canadian deep geologic repository (DGR) concept for long-term safe storage and isolation of used nuclear fuel incorporates a multi-protective engineered barrier system. However, due to the inevitable presence of microorganisms and their metabolic products in a DGR, the integrity of the containers, and hence the repository, might be compromised. Therefore, the emphases of this thesis are to characterize and identify the microbial populations present in bulk and highly-compacted Wyoming MX-80 bentonite, to determine the conditions under which the survival and activity of microorganisms in highly-compacted bentonite clay (one of the engineered barriers) will be minimized or regulated, and to observe the microbial capacity to interact with bentonite particle under nutrient regime (clay-microbe aggregation study). To achieve these, culture-dependent and molecular biology methods (e.g., 16S rRNA sequencing), a range of analytical chemistry assays (e.g., sulfate turbidimetric method), pressure cell studies, microscopic technique (e.g., confocal laser microscopy (CLSM)), particle size analyses and laboratory-scale enrichment (or microcosm) assays were carried out. Culture-dependent techniques revealed the presence of spore-forming bacterial isolates belonging to phyla Actinobacteria and Firmicutes in bulk MX-80. Interestingly, when MX-80 bentonite was highly compacted, Gram-positive spore-formers were also identified after being exposed to the collective effect of > 2,000 kPa swelling pressure, 0.96 water activity, oxygen-free environment, and ≥ 1.6 g/cm3 dry density conditions for ~ 145 days and ~ 8 years. It was determined that microbial culturability was suppressed at or below background level (i.e., ≤ 2 x 102 Colony Forming Units per g) when the aforementioned parameters were applied and when 50 g/L NaCl solution infiltrated the highly-compacted bentonite (HCB). Sulfate reducing bacteria (SRB) in the HCB, however, were speculated to remain as spores during the incubation period since their microbial counts were similar at different dry densities. The enrichment assays for SRB containing bentonite clay slurry amended with carbon, electron donors and acceptors revealed that lactate was the preferred substrate for sulfidogenesis and that high salinity could impede the same process. Finally, the clay-microbe aggregation study showed that extracellular polymeric substance (EPS) contribute to the clay-microbe aggregation and that nutrient concentration, carbon substrate type and bentonite concentration affect EPS production. Overall, these studies are relevant to DGR operations because the results obtained will assist in understanding the potential consequences of microbial interactions with clay minerals

Canada's Nuclear Crossroads: Steps to a Viable Nuclear Energy Industry

Canada is at an energy and environmental crossroad. Fossil fuels cause environmental damage and the growth potential of large-scale hydroelectricity is limited. Policymakers are reconsidering the merits of nuclear power as both a low-carbon emitting and low-cost base load electricity source. While nuclear power may look like an attractive option, nuclear power must overcome problems such as the high and uncertain cost of construction, dealing with nuclear waste, reactor licensing and regulation, and the future of Canada’s nuclear reactor builder, Atomic Energy of Canada Limited (AECL), a federal Crown corporation.economic growth and innovation, energy and environmental policy

Resistance to Nuclear Waste Disposal: Credentialed Experts, Public Opposition and their Shared Lines of Critique

This article asks the question whether, in regard to controversial technical decision-making, lay public groups advance different kinds of resistance than credentialed experts. This question is explored via a case-study analysis of one of Canada's major public controversies of the past quarter century—nuclear waste disposal. Having arrived on the policy radar in 1977, nuclear waste remained an internal government/nuclear industry matter until terms of reference for a public inquiry were announced in 1989. Several access points for public input followed that announcement: scoping sessions in 1990, comments received during 1994-96 on an Environmental Impact Statement (EIS) prepared by Atomic Energy Canada Limited (AECL), nation-wide public hearings in 1996-97, and ongoing public consultation since 2002. This article focuses on the comments on the EIS, and discusses several lines of shared resistance: the expert judgment of AECL was disputed, the lack of peer review was criticized, accusations of unreliability were made, and general deficiencies in the EIS were attributed to narrow terms of reference and poor institutional culture. This article recommends the use of a dramaturgical approach to technical texts, and reveals the assumptions framing the dualist notion that one can unambiguously separate technical and social criticisms of technical projects.Dans cet article, nous nous interrogeons sur la spécificité des actes de résistance des associations citoyennes lors de controverses techniques. Nous explorons cette question par l’analyse d’une des controverses publiques les plus importantes au Canada au cours des dernières décennies : la gestion des déchets nucléaires. Arrivés sur la scène politique en 1977, les déchets nucléaires demeurent un enjeu limité au gouvernement et à l’industrie nucléaire jusqu’à ce que les termes de références pour une enquête publique soient annoncés en 1989. Les possibilités pour le public de faire valoir son point de vue se multiplient dès l’annonce de l’enquête : des séances d’information en 1990, la réception de commentaires entre 1994 et 1996 sur une étude d’impacts environnementaux (EIE) préparée par Énergie Atomique du Canada Limité (EACL), des audiences publiques à la grandeur du pays en 1996 et 1997, et une consultation publique continue depuis 2002. Cet article s’intéresse aux commentaires sur l’EIE, et discute plusieurs arguments que partagent les associations citoyennes et les experts techniques : la contestation du jugement expert de l’EACL, la critique de l’absence d’évaluation par les pairs, l’accusation de manque de fiabilité, et l’attribution des carences de l’EIE à l’étroitesse des termes de références et à une pauvre culture institutionnelle. L’article recommande une lecture dramaturgique des textes techniques, et révèle les conditions de notre incapacité à séparer clairement les critiques techniques et sociales des projets techniques