Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999. / Includes bibliographical references (leaves 157-165). / This thesis presents experimental results of a megawatt power level, 140 GHz coaxial gyrotron oscillator. The coaxial gyrotron has the potential to transport very high power electron beams and thus achieve higher microwave output power levels than conventional gyrotrons. A TE2 ,3 coaxial gyrotron was designed to operate at 95 kV, 76 A. This tube was tested to high power with the first high power Inverted Magnetron Injection Gun (IMIG). The IMIG electron gun was tested to 10 MW (105 kV, 93 A), which is the highest power level for a non-relativistic gyrotron gun. Operation of the coaxial gyrotron oscillator yielded power levels of greater than 1 MW in two different configurations: with the coaxial conductor (at 92kV, 70 A, and 16% efficiency) and without the coaxial conductor (85 kV,65 A, and 18% efficiency). We also successfully operated this tube in three configurations (empty cavity, radial output, and axial output) with no beam interception. We observed regimes of dominant single mode and multi-mode operation. We also identified electron beam asymmetries and tube alignment as two major issues, which can limit the performance of a coaxial gyrotron. An unexpected source of magnetic field error was found in the magnetization of the stainless steel parts. All these results have led to techniques for improving not only coaxial gyrotrons but also other gyrotron tubes. / (cont.) We also investigated a ferroelectric cathode, which has the potential to achieve higher currents than thermionic cathodes in a simpler, low cost gun. We report the first results on a ferroelectric cathode gun in a magnetron injection gun configuration suitable for use in a gyrotron. It had an annular emitter shape with a diameter of 11.4 cm and a width of 0.25 cm and operated at currents of up to 10 A (1.1 A/cm2) at 8 kV, in 5 Vs flat-top pulses. This result (along with the kiloampere beam obtained at Integrated Applied Physics) demonstrate the scalability of ferroelectric cathodes to large diameter electron beams. Also, the first ever microwaves from a ferroelectric cathode were generated in a collaboration experiment at Tel Aviv University. Finally, we developed a theory to explain the emission process from ferroelectric cathodes. The experiments reported have shown the suitability of ferroelectric cathodes for future microwave generation experiments. / by Rahul N. Advani. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999. / Includes bibliographical references. / by Cynthia Fu-Yu Chuang. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 74-77. / by Mark William Zimmermann. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1967. / Bibliography: leaves 169-173. / Edward Ernest Pilat. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999. / Includes bibliographical references. / An integrated model has been developed to evaluate the effect of reactor flux, fluence, and other operating conditions on crack growth rates in austenitic stainless steels in boiling water reactor (BWR) environments. The model evaluates the following in order to account for all factors affecting irradiation assisted stress corrosion cracking. *water chemistry including radiolysis and hydrogen injection *radiation induced segregation of the metal *radiation hardening of the metal *crack tip strain rate of a growing crack *dissolution rate at the crack tip following passive film rupture. The results of each of these models are combined to determine the crack advance rate for the given conditions. Environmentally assisted cracking (EAC) is a phenomenon where a combination of aggressive environment, susceptible material, and significant tensile stress result in accelerated degradation, including stress corrosion cracking (SCC), and hydrogen embrittlement. The EAC model is based on first principles electrochemistry and physical metallurgy. The effect of neutron and gamma radiation dose is included so that irradiation assisted stress corrosion cracking can be studied. By integrating the bulk chemistry with crack tip processes, the crack growth behavior of an aqueous system can be completely characterized. The model integrates chemistry and mechanical behavior to allow the study of EAC in general. / (cont.) EAC phenomena of interest include anodically driven stress corrosion cracking as well as cathodically driven hydrogen embrittlement. The model is able to predict measured data in the literature with good accuracy and precision. It predicts the effects of dose-rate and accumulated dose on stress corrosion cracking in BWRs. This model contributes to the field of crack growth modeling by creating a complete picture including all the major factors effecting crack growth in irradiated systems. / by Thomas Todd Pleune. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999. / Includes bibliographical references (p. 215-220). / by Laura Grace Murphy. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999. / Includes bibliographical references (leaves 116-120). / by Mark Andrew Sitek. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999. / Includes bibliographical references (leaves 79-80). / by Gongyin Chen. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1986. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Bibliography: leaves 95-97. / by Matthew Jay Schor. / M.S.

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