HETEROGENEOUS SODIUM FAST REACTOR DESIGNED FOR TRANSMUTING MINOR ACTINIDE WASTE ISOTOPES INTO PLUTONIUM FUEL By SAMUEL EUGENE BAYS A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2008 1 © 2008 Samuel Eugene Bays 2 To Nikki. 3 ACKNOWLEDGMENTS I would like to thank my faculty advisor, James Tulenko, for his constructive comments and guidance of this work. I would also like to thank the other members of my advisory panel, Edward Dugan, Samim Anghaie, Ronald Baney and Steve Herring for their sensible recommendations. I would like to especially thank and recognize Steve Herring for his technical guidance and support of this work. I greatly thank and appreciate Idaho National Laboratory for its financial support of this dissertation project. Thanks go to Douglas Crawford and David Nigg for their management of projects and activities in which this work supported. I thank Doug Porter, Mitch Meyer, Steve Hayes, Jon Carmack and Rory Kennedy for their technical feedback and discussions on transmutation and fast reactor fuels. Special thanks are given to Pavel Medvedev for his input on establishing the fuel performance criteria of the transmutation targets. Special thanks are given to Bevin Brush and Thomas Johnson for their technical insight of fuel handling and separations operations at the EBR-II fuel cycle facility. Special thanks are given to Steve Piet, Gretchen Matthern and David Shropshire for their technical insight into the system dynamics and economics of closing the domestic and international fuel cycles. Special thanks are given to Roald Wigeland, Giuseppe Palmiotti and Massimo Salvatores for their technical insight into reactor physics and design methodologies of sodium fast reactors. Many thanks are given to my friends and colleagues of the INL fuel cycle analysis team: Mehdi Asgari, Rodolfo Ferrer, Benoit Forget and Michael Pope for the excellent studies and results that we have produced over the last two years. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS ...............................................................................................................4 LIST OF TABLES...........................................................................................................................9 LIST OF FIGURES .......................................................................................................................12 ABSTRACT...................................................................................................................................22 CHAPTER 1 INTRODUCTION ..................................................................................................................24 Motivation and Objectives......................................................................................................26 Transmutation Physics............................................................................................................31 Neutron Spectrum Influence on Transmutation Behavior...............................................32 Transmutation and Nuclear Stability...............................................................................36 Isotopic Aspects of Repository Impacts..........................................................................39 Background on Previously Proposed TRU Burning SFRs.....................................................41 The Advanced Burner Reactor Design Concept .............................................................43 Transmutation Target Designs: Radial Blankets and Moderated Targets......................45 Transmutation Target Designs: Axial Blankets and Axial Targets................................48 Transmutation Based Reactivity Control Concept..........................................................49 Design Rationale of an Axial Heterogeneous Fast Transmutation Reactor ...........................52 Compensation for Inherent Positive Void Reactivity Feedback .....................................53 Benefits of Axial Targets for a Dedicated MA Burner Core Design ..............................54 Technology Compatibilities and Synergies............................................................................58 Actinide Partitioning: PUREX and UREX.....................................................................59 Pyroprocessing and the Integral Fuel Cycle....................................................................61 Assumptions for Using Transmutation Targets in SFRs.................................................63 2 COMPUTATIONAL METHODS AND FAST REACTOR PHYSICS................................66 Calculations and Fuel Cycle Modeling...................................................................................66 Fast Reactor Equilibrium Fuel Cycle Calculations Using the REBUS Code .................68 Light Water Reactor Spent Fuel Calculations Using the TRITON Code .......................72 Scoping Calculations and Benchmarking Using the MCNP Code .................................73 Physics of the Reference Metal Fueled Advanced Burner Reactor........................................74 Conversion Ratio and High Leakage Cores ....................................................................75 Conversion Ratio and High TRU Enriched Fuels ...........................................................80 Physics of the Axially Heterogeneous Fast Transmutation Reactor ......................................82 Axial Targets and Axial Leakage Recovery....................................................................82 Axial Targets and Minor Actinide Conversion ...............................................................85 Combining Leakage and Capture Effects...............................................................................90 5 3 AXIAL TARGET DESIGN ANALYSIS...............................................................................93 Waste Management Philosophies and Conversion Ratio Definition......................................93 Transmutation Based Reactor Design ....................................................................................96 Transmutation Targets and Accompanying Fuel Cycle ..................................................99 Transmutation Target Physics .......................................................................................103 Parametric Study...................................................................................................................106 Effects of Pin Diameter and Core Height......................................................................107 Effects of Moderating Pins............................................................................................111 Tall and Flattened Axial Heterogeneous Core Designs........................................................115 Radial and Axial Power Profiles ...................................................................................116 Reactivity Feedbacks.....................................................................................................123 Fuel Performance Indicators..........................................................................................125 Final Down-Selection: The AHFTR Design .......................................................................128 Fuel Cycle Performance of the Final AHFTR Design ..................................................129 Reactor Performance Characteristics of the Final AHFTR Design...............................132 Transmutation Analysis of the Final AHFTR Design...................................................135 4 REACTOR REACTIVITY CONTROL STRATEGY.........................................................139 Tc-99 versus B-10 as a Control Rod Neutron Poison...........................................................139 Control Assembly Design.....................................................................................................143 Traditional SFR Control Assembly Design: B4C Ultimate Shutdown Assembly........143 Technetium Based Primary Control Assembly Design.................................................144 Gas Expansion Module..................................................................................................148 Control Rod Worth ...............................................................................................................150 Reactivity Worth of Boron versus Technetium.............................................................155 Top versus Bottom Inserted Shim Rods........................................................................156 Axial Power Tilt and Shim Rod Insertion .....................................................................157 Other Reactivity Feedbacks..................................................................................................157 Axial Fuel Expansion ....................................................................................................160 Radial Fuel Bowing.......................................................................................................161 Technetium Transmutation Rate...........................................................................................164 5 DIFFUSION VERSUS TRANSPORT BENCHMARKS....................................................167 Diffusion and Transport Methods.........................................................................................168 Flux Spectrum Analysis ................................................................................................170