Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2000. / Includes bibliographical references (p. 379-382). / Experimental and analytical studies were performed to investigate the behavior of uranium with bacteria in an anaerobic environment. Laboratory studies used Shewanella putrefaciens because of its ability to grow rapidly in aerobic conditions and reduce metals in anaerobic conditions. Under anaerobic conditions, Shewanella putrefaciens use aqueous uranium as the electron acceptor in lieu of oxygen. The reduction of U(VI) to U(IV) removes uranium from solution and forms an insoluble compound known as uraninite. Ultraviolet/Visible Spectroscopy was used to analyze uranium ion complexion with several oxazine dyes that included Brilliant Cresyl Blue, Celestine Blue, and Gallomine Triethoiodide. Complexion and resultant color changes with U(VI) and U(IV) with the dye solutions were tested at a variety of pH levels. The dye behavior was evaluated for future use as a visible reduction indicator for microbial reduction when performing direct plating experiments. These studies showed the best visual indicator to be Celestine Blue. Significant absorbance changes in the 400 to 800 nm wavelength range for Brilliant Cresyl Blue and Gallomine Triethoiodide solutions were not detected. X Ray Diffraction and Electron Microprobe Spectroscopy characterized the solid precipitates by the bacteria. The dark black precipitate exhibited visible characteristics of both UO2(s) and U3O8 (s). Electron microprobe showed a very small crystal formed by the bacteria, but was inconclusive with respect to the elemental composition of the mineral. The XRD spectra determined that precipitate was uranium dioxide U02(s). The investigation included a time phased uranium isotope analysis in the precipitate and supernatant samples. Thermal Ionization Mass Spectrometry (TIMS) measured the uranium isotopic ratio of 238U /235U to determine if microbial reduction of U(VI) to U(IV) affected these ratios. The isotopic ratios of both the supernatant and precipitate were measured at times ranging from zero to 95 hours. An enriched uranium solution was created by dissolving an enriched sample of U308(s) in nitric acid. The U308(s) was standard reference material (SRM) from the New Brunswick National Laboratory, and was enriched to roughly 50 percent 235U. The results of the TIMS experiment showed that there was not a detectable level of fractionation. / by Matthew R. Lewis. / S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, February 2001. / Includes bibliographical references (leaves 198-204). / Flow Accelerated Corrosion (FAC) is the most prevalent material degradation mechanism for low carbon steel in steam-water flow systems. The band of uncertainty in predictions of wear rate due to FAC spans one to two orders of magnitude. Such a wide range of uncertainty inhibits the ability to devise safe and economical repair and replacement schedules. The goal of this thesis is to reduce uncertainty of predictions of wear caused by FAC. Reduction in the uncertainty in FAC wear rate predictions is achieved through the development of a new predictive FAC model, the incorporation of this model in a flow system analysis environment, and the use of this environment to identify improved methodologies for predicting FAC wear rate. The new FAC model is based on a published empirical model, published data, and physical mechanisms identified to be significant in the wear process. The new FAC model is shown to have less uncertainty for single phase lab data and single and two phase plant data. The flow system analysis environment is an interactive program that calculates parameters relevant to the FAC phenomenon based on plant description. Functionality of this environment is validated for each of the four calculations it performs: thermodynamic, thermal hydraulic, chemistry, and degradation rate. Additionally, this environment can be used to analyze contributions to uncertainty that are not yet identified. This environment was used to analyze the contribution to uncertainty from the current method of incorporating chemistry parameters in predictions of FAC wear. Based on this analysis, suggestions are made to improve these methods, thereby reducing prediction uncertainty and improving the knowledge necessary for safer and more economical plant operation. / by Mark Johan van der Helm. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2000. / Includes bibliographical references. / Fuel cladding for water-cooled power reactors must meet certain requirements for optimal performance. To function in the extreme conditions typical of a nuclear reactor core the material used must be corrosion resistant, have low thermal neutron cross section, and high strength. Corrosion resistance is one of the most important parameters for reactor materials. From the beginning of the use of reactors, engineers have been faced with the problem of excessive corrosion in several different forms. In recent years, a peculiar corrosion phenomenon has increased in significance. Several occurrences of local corrosion enhancement of zirconium-base alloys in proximity to other components have been observed. This corrosion enhancement talcs the form of a "shadow" of a metal component in proximity, hence its name, "shadow effect." Although much recent attention has been given to the shadow effect, it has been known since the sixties, but has only lately been considered a possible threat to material integrity. Today the interest in local corrosion enhancement due to the shadow effect and its implications for in-core performance of cladding and structural material is increasing worldwide. International experience has shown that the phenomenon has occasionally resulted in serious corrosion problems threatening material integrity. In order to prevent future obstruction from the phenomenon an understanding of the shadow effect needs to be developed. This becomes important in today's rapid expansion of aggressive reactor environments with higher burn-up and the need for longer fuel residence times for more economical runs. This project was conducted at MIT, funded by ABB Atom, which had the goal of identifying the basic mechanisms of the shadow effect. The MIT research reactor MITR-11 was used to simulate BWR core coolant conditions. The sample train included Zr-2- alloy with various surface treatments. Different counter electrodes surrounded each cladding piece. They were high and low beta emitters, inert material and Zircaloy-2 in contact and non-contact at various separation distances. Post-irradiation examination of the cladding pieces showed: * Beta-radiation is not the main mechanism for the shadow effect. * Shadow corrosion is partly dominated by an electrochemical mechanism. * Radiolysis plays an important role for the formation of shadow corrosion. / by Anthony R. Châtelain. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999. / Includes bibliographical references (p. 165-167). / Southeast Asia needs strong financial and infrastructure bases for continuous development. in the next century. Although the turmoil of the 1997 Asian financial crisis slowed down economic growth the region is recovering gradually, and will need increasing energy supplies in the future. In the electricity sector, which has had to expand more slowly than it did in the 1980s, the main focus has been changing from how to satisfy the growing demand for high reliability to how to cut the cost of electricity. Under these circumstances, we examine the effective role of nuclear power, which can contribute to the stable supply of electricity and still meet the requirement of low emissions. A method of multi-attribute analysis is proposed to assess the feasibility of introducing nuclear power in combination with other generating facilities, such as natural gas, coal, oil and hydro. Capacity expansion plans from the year 2000 through 2020 in Japan Thailand, and Vietnam, which are composed by a technique of dynamic expansion planning, are evaluated on the basis of total costs, emissions, waste and energy security. In addition, the impact of electricity trade in Southeast Asia on the role of nuclear power is examined. This work concludes that nuclear power is compatible with the energy, economic and environmental conditions that may prevail in the region. The factors that promote nuclear power are: its low variable costs, the need for financial stability against unexpected economic disruptions of gas prices low interest rates to finance its capital needs and the limitation on CO2 emissions due to international concerns about global climate change. / by Tatsuro Kobayashi. / S.M.

Thesis (Nucl. E.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1990. / Includes bibliographical references (leaves 177-181). / by Arivaldo Antonio Rios Esteves. / Nucl.E.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1986. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 208-212. / by Eric Hans Esarey. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1986. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 322-326. / by Tae Sun Ro. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1986. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Bibliography: v.2, leaves 294-303. / by Renato Salang Ornedo. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1985. / Bibliography: leaves 229-230. / by Richard Dean Wittmeier. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 194-197. / by Han-Sem Joo. / Ph.D.