Thermal hydraulic design and analysis of a large lead-cooled reactor with flexible conversion ratio

• Main Author: Nikiforova, Anna S., S.M. Massachusetts Institute of Technology
• Other Authors: Neil E. Todreas and Pavel Hejzlar.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2010
• Subjects: Nuclear Science and Engineering.
• Online Access: http://hdl.handle.net/1721.1/53277

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008. === Cataloged from PDF version of thesis. === Includes bibliographical references. === This thesis contributes to the Flexible Conversion Ratio Fast Reactor Systems Evaluation Project, a part of the Nuclear Cycle Technology and Policy Program funded by the Department of Energy through the Nuclear Energy Research Initiative. The goal of this project is to develop conceptual designs of fast flexible conversion ratio reactors using lead and liquid salt coolants and compare the results with the gas cooled fast reactor developed in an MIT NERI project and the sodium cooled reactor under development at ANL. This thesis is the summary of the design and analysis of the lead-cooled reactor portion of the project. Core designs that fit in the same reactor plant were executed for two limiting conversion ratios: (1) near zero to transmute legacy waste and (2) near unity to operate in a sustainable closed cycle. To reap the benefits of economy of scale, a large power rating of 2400MWt was set as the target thermal power for both reactor designs. In addition, the achievement of inherent reactor shutdown in unprotected accidents (without scram) was set as a desirable goal. The core employs transuranic metallic fuel. The large pool vessel contains four intermediate heat exchangers (IHX) that couple the primary system to an efficient and compact supercritical CO2 power conversion system. To prevent CO2 from entering the core in case of intermediate heat exchanger tube rupture, a dual-free level design for the primary vessel is adopted. Ultimate decay heat removal is accomplished by passive means through an enhanced reactor vessel auxiliary cooling system (RVACS) complemented by a passive secondary cooling system (PSACS). === (cont.) The transient simulation of station blackout (SBO) using the RELAP5-3D/ATHENA code shows that inherent shutdown without scram can be accommodated within the cladding temperature limit by the enhanced RVACS and PSACS by removing a fraction of decay power with the PSACS. The PSACS was designed such that the balance between two limiting cases was achieved: (1) peak cladding temperature limit is satisfied during unprotected station blackout with a minimum (two) number of PSACS trains operated, and (2) the minimum coolant temperature is kept above the freezing point with a maximum (four) number of PSACS trains operated. The PSACS design satisfies the conditions of both unity and zero conversion ratio cores. The other SBO accident conditions are bounded by the above cases. In addition, two other transients are considered: loss-of-flow accident (LOFA) and inadvertent reactivity insertion transient (UTOP). Both reactors show good performance during these additional transients. === by Anna S. Nikiforova. === S.M.