Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2003. / Includes bibliographical references (p. 59-60). / An experimental study was conducted to determine the practicality of various unit operations for fluorination of uranium dioxide. The objective was to prepare ammonium uranium fluoride double salts from uranium dioxide and ammonium bifluoride, then decompose these salts to uranium tetrafluoride through heating to temperatures near 425 °C in either a fluidized bed or a stirred bed. Fluorination in the stirred bed was attempted without pretreatment of the reagents. For the fluidized bed experiments, reagents were ball-milled prior to being heated in the bed. Experiments were conducted in either argon or 4% hydrogen in argon. The ball mill appeared to be an effective technique for fluorinating uranium dioxide with ammonium bifluoride. Samples changed color from brown to bright green, and no oxides could be detected in the x-ray diffraction pattern of the product. It was found that stainless steel is a suitable material of construction for reaction vessels, whereas mild steel parts corroded quickly. Only a small degree of fluidization provided adequate mixing in fluidized beds, but a paddle mixing the stirred beds left an unmixed region around the bed perimeter. Results from the stirred beds showed the initial fluorination reaction completed only when the reagents were heated to 110 °C for at least three hours under argon. Decomposition took place under argon with a temperature ramp up to 425 °C. The product UF4 contained less than 1% oxide as an impurity, and the decomposition appeared to be complete. Fluidized beds were run with both argon and 4% hydrogen in argon as carrier gases. Experiments with 4% hydrogen in argon produced uranium tetrafluoride, with ammonium uranium pentafluoride and uranium dioxide as impurties. Experiments in argon produced uranium tetrafluoride, with uranyl difluoride, ammonium diuranyl pentafluoride and triuranium octoxide as impurities. Minimum temperatures and times needed to decompose the double salt in the fluidized beds were 200 minutes at 115 °C, a 500-minute ramp to 425 °C, and 200 minutes at 425 °C. The intermediate double salt produced at 110 °C appeared to be triammonium uranium septafluoride. / by Charles Burnett Yeamans. / S.M.

Massachusetts Institute of Technology. Dept. of Nuclear Engineering. Thesis. 1969. Ph.D. / Bibliography: leaves 307-312. / Ph.D.

Massachusetts Institute of Technology. Dept. of Nuclear Engineering. Thesis. 1970. M.S. / Bibliography: leaf 59. / M.S.

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999. / Includes bibliographical references (leaf 157). / For U.S. nuclear power stations to continue to generate electricity they must operate both safely and economically. Although the average safety and economic performance of U.S. power stations has improved over the past several years, some plants have not reached or have not sustained high performance levels. Stations achieving sustained high performance levels were identified by an analysis of safety and economic performance data. The core attributes considered necessary to achieve and maintain this level of performance were identified by interviews with executives from the stations and by analysis of effective programs and practices, Core attributes for long-term sustained high performance were determined to be: -- Strong teamwork among the plant staff. -- Extremely reliable equipment operation. -- Clear, effective communication throughout the station. -- Effective use of operating experience and benchmarking. -- Knowledgeable and involved station managers. -- Training focused on improving performance. -- Constant focus on safe plant operation. Recommended methods to identify shortfalls and improve core attribute performance at stations that have not achieved sustained high performance are self-assessment, development of station-wide core principles, and management and supervisory training. / by James E. Lynch. / M.Eng.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1996. / Includes bibliographical references (leaves 143-144). / by Boris Lekakh. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1994. / Includes bibliographical references (p. 185-186). / by Hernan Gerardo Trosman. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1992. / Includes bibliographical references (2nd v., leaves 394-400). / by Keung Koo Kim. / Ph.D.

Massachusetts Institute of Technology. Dept. of Nuclear Engineering. Thesis. 1973. Ph.D. / Includes bibliographical references. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1991. / Includes bibliographical references (leaf 147). / by Raymond Todd Klann. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1991. / Includes bibliographical references (leaves 128-130). / by Abdelouahab A. Dehbi. / Ph.D.