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: 8 th Information Exchange Meeting OECD Nuclear Energy Agency Las Vegas, Nevada; Nov. 9-11, 2004 The submitted manuscript has been authored by a contractor of the U.S. Government under contract DE-AC05-00OR 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 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

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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 6 Processing Costs and Risks are Reduced with Old Spent Nuclear Fuel  Decreased heat and radioactivity  Requirements for separation are greatly reduced or eliminated for some mobile radionuclides  Krypton  Tritium  Cesium  Strontium Time (years) Decay Heat Radioactivity Decay Heat (kW/MTIHM) Radioactivity (10 6 curies/MTIHM)

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 7 Storage (Time) is a Potentially Usable Transmutation Strategy Long (> 30-year) Decay Period Alters Transmutation Path Building of heavier isotopes is suppressed and regeneration of fissile isotopes occurs (Reduces LWR thermal P/T penalty) 241 Am 242 Am 242 Pu 242 Cm 238 Pu 239 Pu 17% 83% 241 Pu 70 % fission 244 Cm 244m Am 243 Am 242 Pu 241 Pu Short-cooled SNF transmutation Storage transmutation T 1/2 = 18.1 y T 1/2 = y

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 9 Production (Recycle) Rates of Key Radionuclides with 30-year Decay Cycles

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 10 Comparison of 5- and 30-Year-Decay Production (Recycle) Rates

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 11 Comparison of 5- and 30-Year-Decay Production (Recycle) Rates with Time

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 12 Limited Facilities Are Required for a Store and LWR-Irradiate P/T Strategy Existing LWRs→ Reprocessing- fabrication plant→ ←SNF dry storage

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY 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