Browsing by Subject "Radioactive waste disposal"
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Item Finite element evaluation of thermal stresses during the solidification of a glass pour(Texas Tech University, 1997-08) Li, JianminThe purpose of this thesis is to determine the temperature history, thermal stress history, and the susceptibility to fracture of glass (borosilicate) as it is poured (in a liquid state) into a canister and allowed to cool into a solid state. The general purpose finite element code ABAQUS was utilized to simulate the glass pour problem. The thermomechanical problem was solved using an axisymmetric geometry and with proper boundary conditions. Three specific problems were addressed: (1) determination of temperature history in the glass pour as it was being poured into a stainless steel canister; (2) determination of the thermal stress history in the glass as it solidifies and cools to room temperature; and (3) assessment of potential for fracture in the solidified glass as a result of the induced thermal stresses. Phase change effects were not considered in the model. In determining the temperature history of the glass pour, heat loss due to natural convection and radiation from various surfaces were considered. Once the canister was full, the temperature history was recorded. The recorded temperature history was then used to determine the thermal stress history in the glass pour. Based on the determined thermal stress history, the principal stresses were calculated and compared with the yield strength of glass to determine the potential for crack formation. When determining the thermal stress history in glass, two different sets of boundary conditions were used. The first boundary condition assumes that glass remains in contact vdth the canister wall as it cools down. The second boundary condition allows the glass to separate from the canister wall as it contracts. The fracture analysis results showed that both cases have potential for crack formation. However, the second set of boundary conditions (the set that allows the glass to separate from the canister wall) seems to simulate more realistically the possibility and location of the cracks that may form.Item Isoamethyrin analogues and cyclo[n]pyrrole as sensors for cations and anions(2007-05) Melfi, Patricia Jennifer, 1979-; Sessler, Jonathan L.The increased worldwide interest in nuclear power and the politically charged threat of nuclear weapons release has made understanding the components, as well as the waste, of nuclear energy an important area of research. More specifically, the identification and selective extraction of the dioxoactinide cations uranyl (UO₂²⁺) and plutonyl (PuO₂⁺), low valent actinides scuh as Am³⁺ or Cm³⁺ and various anions, such as pertechnetate (TcO₄⁻), is essential in the event of a weapons release or the spill of nuclear waste. It has been previously demonstrated that the expanded porphyrin [24]hexaphyrin(1.0.1.0.0.0), commonly referred to as isoamethyrin, displays a dramatic color change, from golden yellow to red, upon coordination of uranyl, neptunyl and plutonyl cations. Chapter 2 details quantitative investigations of isoamethyrin with the uranyl cation as well as the interactions of isoamethyrin with other, potentially competing, cations. This work was carried out in order to assess the ability of isoamethyrin to serve as a colorimetric sensor for the actinide cations. Chapter 3 describes the synthesis and properties of periphery-modified isoamethyrin analogues. The addition of functional groups to this expanded porphyrin allows for immobilization onto a solid support and may enhance its utility as a sensor. Chapter 4 presents the preliminary investigations into the metalation and anion binding properties of a new series of macrocycles, the cyclo[n]pyrroles. Chapter 5 provides experimental methods and characterization data.Item Metal cation complexation and separation with macrocyclic polyether ligands(Texas Tech University, 2004-12) Vogel, Howard FAt Hanford, Washington, the Department of Energy maintains a site that contains approximately 6x10^7 gallons (2 x l0^8 liters) of waste left over from the development of nuclear weapons after WWII. This volume of material is too great to be stored in Yucca Mountain. Separation of the high-level radionuclides from the bulk of the material will allow the remainder to be treated and disposed of as low-level waste. Once separated, the high-level nuclides are then available for use in commercial applications, such as medical imaging and remote power plants. This study explores the use of crown and lariat ethers for the separation of metal ions. A large number of compounds varying in specific structural aspects are studied using isothermal titration calorimetry (ITC), which directly determines the association constant, stoichiometry, and enthalpy of each metal-ligand system. Augmenting the ITC study is the intense study of a small selection of compounds. These compounds are studied under various conditions using a variety of techniques, such as ion-selective electrodes (ISE) and solvent extraction (SE), allowing for a fuller understanding of their association behavior. The presence of metal ion is our world is ubiquitous. Some of these metals are benign, or even necessary for life. Others are harmful in minute quantities. The ability to selectively remove specific metal ions from waste streams, the environment, and our bodies will be an important process in years to come.Item Perceptions of risk in siting nuclear waste facilities: a localized perspective(Texas Tech University, 2000-08) Skopek, Tracy AnnThe issue of nuclear waste continues to reappear among the general public in America as a salient issue. Hazardous and toxic waste disposal is of increased concern to many citizens due to a continued need for disposal facilities as well as safety issues associated with long-term disposal facilities. The new trend toward environmental concern in recent years has led to a shift in values, which emphasize a balance between economic development and environmental preservation. Because of this shift, there has been increased public involvement in environmental issues, especially in the nuclear waste disposal policymaking process. Public support is crucial in developing a policy to site high level nuclear waste repositories since they typically must be placed near at least a few communities. This dissertation seeks to model the construct of how citizens in local communities perceive the risks when faced with the placement of a potential nuclear hazard. Using survey data from Amarillo, Texas (the Pantex Nuclear Facility) and Tricities area, Washington (Hanford Nuclear Reservation), the hypothesis that communities with similar historical associations with nuclear facilities in their area tend to build local cultures around those associated risks and are likely to view a proposed new facility differently, with less fear, than areas without the nuclear context. This view is an important element of nuclear waste siting policy since the Department of Energy tends to favor placing new nuclear waste repositories in areas with existing facilities, since they feel there is less resistance. However, this practice can not continue as the areas with such facilities is limited. But, by understanding how individuals in those areas ultimately formulate their attitudes toward the risks, steps can be taken to better handle local oppositional behavior, or NIMBY (not in my backyard), as it occurs in facility siting. The research findings in this dissertation indicate that the level of trust individual have in their local leaders is the most important indicator of how they will perceive the risk associated with a nuclear waste facility. In particular, the more they trust local leaders, the lower their risk perception.Item Synthesis of new separating agents for nuclear materials(Texas Tech University, 1998-08) Nam, JaewookSynthetic methods for the preparation of complexing agents for the separation of radionuclide materials are described in this dissertation. Several series of new bifunctional anion-exchange resins were prepared by reaction of Reillex™ 402 po]y(4-vinylpyridine) resin with alkylating agents CL>-Br(CH2)nQ^ in Q"^ = trimethylammonio. trimethylphosphonio, and pyridinium groups. By variation of the number of methylene groups in the spacer, the distance between the two anion-exchange sites was systematically varied. The structural variations in these bifunctional anion-exchange resins were made to investigate their Pu(IV) sorption behavior from nitric acid media. Partial substitution of linear poly(vinylpyridine)with hydrophilic groups provided new water-soluble polymers which have potential for use in metal separation using ultrafiltration membranes. For the cesium extraction from acidic nitratemedia, several series of macrocyclic polyether compounds which have oxygenated, aliphatic side arms were prepared. Acylation of dibenzo-18-crown-6 (or dibenzo-21-crown-7) and subsequent reduction provided new carbon atom-linked side armed cyclic polyether extractants. Several approaches to the synthesis of oxygen atom-linked side armed cyclic polyether extractants were explored with the model compound Sesamol. Although results of the model studies were promising, all attempts to extend the methods to the preparation of oxygen atom-linked side armed crown ethers were unsuccessful.Item The United States, Texas, and high-level radioactive waste disposal(Texas Tech University, 1999-05) DeKay, Todd R.There are three broad reasons which explain why the topic of nuclear waste is a neglected historical field. First, even though radioactive waste has been accumulating since the Manhattan Project, its relative danger seemed inconsequential until the early 1970s. The atomic blasts that ended World War II left the United States, according to Edward R. Murrow, in a state of "uncertainty and fear" and with a sense "that the future is obscure and survival is not assured." This fearful uncertainty led the United States and the Soviet Union into the Cold War in which both combatants concentrated on the construction of nuclear weapons. During the decades long struggle, the possibility of a nuclear war overshadowed the dangers associated with the radioactive waste.