Can Thermal Reactor Recycle Eliminate the Need for Multiple Repositories?

1. Can Thermal Reactor Recycle Eliminate the Need for Multiple Repositories? C. W. Forsberg, E. D. Collins, C. W. Alexander, and J. Renier Actinide and Fission Product Partitioning and Transmutation: 8th Information Exchange MeetingOECD Nuclear Energy AgencyLas Vegas, Nevada; Nov. 9-11, 2004 The submitted manuscript has been authored by a contractor of the U.S. Government under contract DE-AC05-00OR22725. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes. File name: SNF Processing: P-T.Nevada.Nov04

2. The Existing Reactor Fleet is Made of LWRs: It Is the Only Near-Term Option for Waste Partitioning and Transmutation (P/T) • Economics currently favor LWRs • Fast-reactor capital costs are greater than LWRs • Uranium prices have remained low because of advances in uranium mining technologies • Introduction date for fast reactors is uncertain • LWRs imply lower P/T deployment costs, if the technology is viable

3. There are Multiple LWR Transmutation Strategies • Thermal-neutron reactor transmutation strategies • Low-enriched LWR fuels • High-enriched uranium driver fuel (demonstrated at SRS and HFIR with the production of Californium) • Transmutation with time (irradiation and storage) • One such option described herein

4. Basis For ORNL Decay and LWR-Irradiate P/T Strategy Large U. S. inventory of old SNF Simpler processing of old SNF Decay of shorter-lived actinides

5. The U.S Has A Massive Existing Inventory of SNF • Current inventory ~45,000 MTIHM • SNF generation rate is ~2000 MTIHM/year • If one large reprocessing plant (2000 tons/year) is constructed and the oldest fuel is processed first, the plant will receive 40 to 50 year old SNF on a steady-state basis

6. Processing Costs and Risks are Reduced with Old Spent Nuclear Fuel 2.5 12 10 2.0 Radioactivity 8 1.5 Radioactivity (106 curies/MTIHM) Decay Heat (kW/MTIHM) 6 1.0 4 Decay Heat 0.5 2 0 0 1 2 5 10 100 Time (years) • Decreased heat and radioactivity • Requirements for separation are greatly reduced or eliminated for some mobile radionuclides • Krypton • Tritium • Cesium • Strontium

7. Storage (Time) is a Potentially Usable Transmutation Strategy Long (> 30-year) Decay Period Alters Transmutation Path Short-cooled SNF transmutation 241Pu  242Pu 243Am 244mAm 244Cm T1/2 = 18.1 y 242Pu 17% Storage transmutation 241Pu 241Am 242Am 70 % fission T1/2 = 14.36 y 83% 242Cm 238Pu 239Pu • Building of heavier isotopes is suppressed and regeneration of fissile isotopes occurs (Reduces LWR thermal P/T penalty)

8. A Store and LWR-Irradiate P-T Scenario Was Evaluated • Only fission products go into the repository • Stored Pu in spent fuel (~ 98% of inventory) is protected by high radiation (“Spent Fuel Standard”) • Both Pu-Np and Am-Cm inventories reach near equilibrium ─“no net production” • Amounts of curium are minimized • Separate Am/Cm targets to minimize fabrication difficulties

9. Production (Recycle) Rates of Key Radionuclides with 30-year Decay Cycles

10. Comparison of 5- and 30-Year-Decay Production (Recycle) Rates

11. Comparison of 5- and 30-Year-Decay Production (Recycle) Rates with Time

12. Limited Facilities Are Required for a Store and LWR-Irradiate P/T Strategy Existing LWRs→ ←SNF dry storage Reprocessing-fabrication plant→

13. Conclusions • LWRs exist • Supports examination of thermal reactor P/T strategies • Several options available • Store and LWR-burn P/T option has several attractive features • Stops growth in the actinide inventory • One repository required for steady-state operation • Minimum investment relative to most other scenarios • Only fission products go into the repository • Actinide inventory in hot SNF • Store and burn P/T option has several constraints • Significant inventory of SNF • Requires dry storage capacity • Exit strategy is complex if no fast reactor