WASH 1097 UC-80 THE USE OF THORIUM IN NUCLEAR POWER REACTORS JUNE 1969 PREPARED BY Brookhaven National Laboratory AND THE Division of Reactor Development and Technology WITH THE ASSISTANCE OF ARGONNE NATIONAL LABORATORY BABCOCK & WILCOX GULF GENERAL ATOMIC OAK RIDGE NATIONAL LABORATORY PACIFIC NORTHWEST LABORATORY For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1.25 FOREWORD This report on "The Use of Thorium in Nuclear Power Reactors" was prepared under the direction of the Division of Reactor Development and Technology, U.S.A.E.C., as part of an overall assessment of the Civilian Nuclear Power Program initiated in response to a request in 1966 by the Joint Committee on Atomic Energy. It represents the results of the inquiry by the Thorium Systems Task Force whose membership included representatives of Babcock & Wilcox Company, Gulf General Atomic Company, the Argonne National Laboratory, the Brookhaven National Laboratory, the Oak Ridge National Laboratory, the Pacific Northwest Laboratory, and the U.S. Atomic Energy Commission. Publication of this report, which provides information basic to the AEC reactor development program, completes one phase of the evaluation effort outlined in the 1967 Supplement to the 1962 Report to the President on Civilian Nuclear Power, issued in February 1967. The 1967 Supplement outlined changes since 1962 in the technical, economic and resource picture and provided background for further study. Specifically, this report represents the consensus of the task force on the potential use of the thorium cycle and the specific thorium fueled reactor designs which have been proposed. It is expected that the relative promise of the use of thorium in reactors, and the future nuclear power industry may be judged on an increasingly sound basis as more information is obtained from the continuing developmental, analytical and engineering efforts. The design data upon which the review was based are limited, particularly those for the molten salt breeder reactor (MSBR) and for the thorium-fueled light-water cooled reactors. In the case of the MSBR, the system is in a very early experimental stage and detailed design information still must be developed. Thus, the review was based upon a very preliminary design which has been changing as a result of continuing technical reassessments and developments. The review of the use of thorium in light water reactors, of necessity, had to be inferred from very preliminary assessments carried out in 1961 - 1964. No detailed designs and only limited technical data are available to directly compare the use of uranium and thorium in the light-water cooled systems. The review of the potential of the use of thorium in light-water reactors was somewhat restricted since the concept studied in the greatest depth, the LWBR, emphasized fuel conservation rather than minimum fuel costs. Therefore, this report does not compare the LWBR concept to the other concepts. The Commission is proceeding with a demonstration of the LWBR concept in the Shippingport reactor, and the results of this demonstration are expected to be available by the middle 1970's. Successful completion of such a breeding demonstration will show the technical feasibility of installing thorium breeder cores in existing and future pressurized light water reactor plants. Information forthcoming from the activities of other task forces, such as those examining the reactor fuel cycle and projections of the future nuclear power economy, may also lead to changes in the predicted potential for the use of thorium in reactors. Also, since thorium-fueled systems are still in the experimental stage, any further data developed may necessitate changes in some of the conclusions of this report. In large measure, the report was based on information provided by the designers of the various thorium-fueled reactors, and the principal participants of the Thorium Systems Task Force included proponents of specific reactor systems. It is recognized that inclusion of membership from national laboratories and industrial organizations actively engaged in the development and promotion of specific reactors can result in a report that reflects the enthusiasm of the proponents of these reactor systems. In May 1968, a draft version of this report was distributed to selected representatives of the reactor plant industry, national laboratories, utilities, USAEC, and other agencies of the federal government for review and comment. The comments were carefully considered in the final preparation of the report. As discussed in the 1967 Supplement to the 1962 Report to the President on Civilian Nuclear Power, the magnitude of the cumulative effort expended to develop light-water reactors, and the success which has been achieved, has resulted in a state and pace of development and production that will make the development of competing systems difficult. The continued economic improvement of light-water reactors, and the successful development of an economic fast breeder would narrow the time span in which an advanced, non-breeding reactor system could alleviate the resource requirements for an economic nuclear power industry. Milton Shaw, Director Division of Reactor Development and Technology THE USE OF THORIUM IN NUCLEAR POWER REACTORS Contents Page 1. Introduction 1 1.1 Background 1 1.2 Objective of Study 1 1.3 Topics Considered 2 1.4 Source of Information 3 2. Summary 5 2.1 Nuclear Characteristics 5 2.2 Reactor Performance Characteristics 6 2.3 Utilization of Nuclear Fuel Resources 7 2.4 Economic Considerations 7 2.5 Status of Reactors Fueled with Thorium 8 2.5.1 HTGR 8 2.5.2 MSBR 9 2.5.3 LWR 10 2.5.4 HWR 10 2.5.5 FBR 10 2.6 General R&D for the Thorium Cycle 11 3. Features of the Thorium Cycle 13 3.1 Fuel Cycles 13 3.2 Nuclear Properties of Fertile and Fissile Isotopes 16 3.2.1 Properties in a Thermal Spectrum 16 3.2.2 Properties in a Fast Spectrum 19 3.3 Advantages of the Thorium Cycle for Applications in Thermal-Spectrum Reactors 20 3.3.1 Introduction 20 3.3.2 Fuel Conversion Ratio 21 3.3.3 Speeific Fissile Inventory 22 3.3.4 Fuel Exposure Time 23 3.3.5 Plant Efficiency 23 3.4 The Thorium Cycle in Fast-Spectrum Reactors 24 3.4.1 Introduction 24 3.4.2 Thorium as a Fertile Material 24 Page 3.4.3 U-233 as a Fissile Material 26 3.5 Transition from the Uranium to the Thorium Cycle 26 3.6 Summary 27 4. Nuclear Fuel Resources, Requirements, and Economics 29 4.1 Introduction 29 4.2 Nuclear Fuel Resources 29 4.3 Civilian Nuclear Power Growth 33 4.4 Reactor Uranium Requirements 34 4.5 Economics 37 4.6 Fuel Strategy 44 4.6.1 Crossed-Progeny System 47 4.6.2 The Thorium Cycle in a Growing FBR Economy 49 4.6.3 The Longer-Range Potential for Thorium 49 4.7 Summary 50 5. Utilization of the Thorium Cycle in Specific Reactor Types 51 5.1 Introduction 51 5.2 High Temperature Gas Cooled Reactor 51 5.2.1 General Description of the HTGR 51 5.2.2 Economics of the HTGR Thorium Fuel Cycle 55 5.2.3 Status of the HTGR Technology 58 5.2.4 R&D Required for the HTGR 63 5.3 Molten Salt Breeder Reactor 64 5.3.1 Introduction 64 5.3.2 Description of Single-Fluid MSBR 65 5.3.3 Nuclear Design 74 5.3.4 Fuel Processing 76 5.3.5 Status of the Molten Salt Reactor 79 5.3.6 R&D Required for the MSBR 80 5.4 Light Water Moderated Reactor 81 5.4.1 Economics of the LWR Thorium Fuel Cycle 81 5.4.2 Status of the LWR Technology 84 5.4.3 R&D Required for the LWR 84 5.5 Heavy Water Moderated Reactor 84 5.5.1 General Description of an HWOCR 86 5.5.2 Economics of the HWOCR 86 5.5.3 Status of HWR Technology 88 5.5.4 R&D Required for Pressure Tube HWR 90 5.5.5 Startup Period for the Pressure Tube HWR 90 5.6 Fast Breeder Reactor Using Thorium Fuel Cycle 91 5.6.1 Introduction 91 5.6.2 Nuclear Data Pertinent to the Thorium Fuel Cycle in a Fast Spectrum 91 5.6.3 Reactor Design Studies 92 5.6.4 Summary and Conclusions 93 6. General R&D for the Thorium Cycle 95 6.1 Reactor Physics 95 6.2 Thorium Fuels 95 6.3 Processing and Recycle of Thorium Fuels 96 Appendix A. Summary and Assessment of Reactor Physics of the Thorium Fuel Cycle 99 Appendix B. Appraisal of Thorium Fuels 111 Appendix C. Reprocessing of Thorium Fuels 119 Appendix D. Identification of Estimates of Nuclear Fuel Resources 125 Appendix E. Molten Salt Breeder Reactor-Two Fluid System 129 References 139 LIST OF TABLES No. TITLE Page 3.1 Thermal-Spectrum-Averaged Eta Values for U-233, U-235, and Pu-329 17 3.2 Typical Spectrum-Averaged Thermal, Epithermal, and Combined Thermal-plus-Epithermal Eta Values for U-233, U-235, and Pu-239 at 600°C 17 3.3 Fission Cross Sections and Eta Values for Fissile Nuclides at Three Neutron Energies 18 3.4 Some Selected Average Cross-Section Parameters for Fuel Nuclides in a Fast Breeder Reactor 19 3.5 Critical Mass, Breeding Ratio, and Sodium Void Effect for a 3000-Liter Metal Fueled Fast Reactor 25 3.6 Comparison of Breeding Performance of Selected 3000-Liter Fast Reactors using Oxide, Carbide and Metallic Fuel 25 4.1 Estimates of U. S. Uranium Fuel Resources 30 4.2 Estimates of U.