Optimization of hydride fueled pressurized water reactor cores

• Main Author: Shuffler, Carter Alexander
• Other Authors: Neil E. Todreas.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2006
• Subjects: Nuclear Engineering.
• Online Access: http://hdl.handle.net/1721.1/33634

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2004. === Includes bibliographical references (leaf 173). === This thesis contributes to the Hydride Fuels Project, a collaborative effort between UC Berkeley and MIT aimed at investigating the potential benefits of hydride fuel use in light water reactors (LWRs). This pursuit involves implementing an appropriate methodology for design and optimization of hydride and oxide fueled cores. Core design is accomplished for a range of geometries via steady-state and transient thermal hydraulic analyses, which yield the maximum power, and fuel performance and neutronics studies, which provide the achievable discharge burnup. The final optimization integrates the outputs from these separate studies into an economics model to identify geometries offering the lowest cost of electricity, and provide a fair basis for comparing the performance of hydride and oxide fuels. Considerable work has already been accomplished on the project; this thesis builds on this previous work. More specifically, it focuses on the steady-state thermal hydraulic and economic analyses for pressurized water reactor (PWR) cores utilizing UZrH₁.₆ and UO₂. A previous MIT study established the steady-state thermal hydraulic design methodology for determining maximum power from square array PWR core designs. === (cont.) The analysis was not performed for hexagonal arrays under the assumption that the maximum achievable powers for both configurations are the same for matching rod diameters and H/HM ratios. This assumption is examined and verified in this work by comparing the thermal hydraulic performance of a single hexagonal core with its equivalent square counterpart. In lieu of a detailed vibrations analysis, the steady-state thermal hydraulic analysis imposed a single design limit on the axial flow velocity. The wide range of core geometries considered and the large power increases reported by the study makes it prudent to refine this single limit approach. This work accomplishes this by developing and incorporating additional design limits into the thermal hydraulic analysis to prevent excessive rod vibration and wear. The vibrations and wear mechanisms considered are: vortex-induced vibration, fluid-elastic instability, turbulence-induced vibration, fretting wear, and sliding wear. Concomitantly with this work, students at UC Berkeley and MIT have undertaken the neutronics, fuel performance, and transient thermal hydraulic studies. === (cont.) With these results, and the output from the steady-state thermal hydraulic analysis with vibrations and wear imposed design limits, an economics model is employed to determine the optimal geometries for incorporation into existing PWRs. The model also provides a basis for comparing the performance of UZrH₁.₆ to UO₂ for a range of core geometries. Though this analysis focuses only on these fuels, the methodology can easily be extended to additional hydride and oxide fuel types, and will be in the future. Results presented herein do not show significant cost savings for UZrH₁.₆, primarily because the power and energy generation per core loading for both fuels are similar. Furthermore, the most economic geometries typically do not occur where power increases are reported by the thermal hydraulics. As a final note, the economic results in this report require revision to account for recent changes in the fuel performance analysis methodology. The changes, however, are not expected to influence the overall conclusion that UZrH₁.₆ does not outperform UO₂ economically. === by Carter Alexander Shuffler. === S.M.