Perspectives on the Back-end of the Nuclear Fuel Cycle: Present and Future

1. Perspectives on the Back-end of the Nuclear Fuel Cycle: Present and Future John Kessler, Program Manager, HLW & Spent Fuel Management (jkessler@epri.com; 704-595-2249) DOE Fission-Fusion Hybrid Workshop, Gaithersburg MDOctober 1, 2009

2. Projected US Commercial Spent Nuclear Fuel (CSNF) Inventory (assumes all existing plants run for 60 years) Current Yucca Mountain legal CSNF capacity limit (63,000)

3. Dry Interim Storage: High Burnup and Extended Storage • EPRI data and models are the basis for enabling: • Dry storage of spent fuel with burnup >45 GWd/MTU • Dominion, Duke Energy, Constellation, … • Dry storage license extended from 20 to 60 years • First license renewal: Surry site • Conclusion: Long(er)-term storage can give us time to introduce new technologies

4. EPRI Yucca Mountain and Generic Disposal Program • Yucca Mountain-specific • Pre- and post-closure • Transportation • Generic disposal • Compare post-closure doses from alternative fuel cycle waste forms • Need for a second repository?

5. DOE Yucca Mountain Repository Design

6. DOE TSPA Results • 10,000-year results • Mean peak dose rate to the RMEI: ~0.2 mrem/yr • ~0.1% of background • ~1% of dose limit • Dominated by (relatively) early failure of DOE/Defense wastes • 1,000,000-year results: • Mean peak to RMEI: ~2 mrem/yr • ~1% of background • ~10% of dose limit • Dominated by commercial spent nuclear fuel (CSNF)

7. EPRI TSPA Results (CSNF only) • 0.04 mrem/y • ~0.01% of background • ~0.2% of dose limit • 1/50th of DOE estimate • Why are EPRI estimates lower? • Reduction of conservatisms EPRI, 2006, Report # 1013444, Fig. 6-3

8. The Peak Dose is NOT Dominated by the Most “Radiotoxic” Species • The geology takes care of the more radiotoxic species • Example: relatively low solubility of many actinides (including Pu) • Sorption on geologic media impedes many radionuclides from movement • Conclusion: inappropriate to use “radiotoxicity” as a measure for potential technical improvements • Closing the fuel cycle • Fission-fusion hybrids, … • Only a handful of radionuclides contribute to long-term dose (not usually minor actinides)

9. Yucca Mountain Peak Dose Estimates Have Been Decreasing. Why? • Additional data • Removal of initial conservatisms • Improved (lower) Np solubility estimates dramatically decreased importance of Np-237 • EPRI drip shield example (next slide)

10. Example of Over-conservatism: Drip Shields are not Necessary • Overestimated the amount of net infiltration; • Overestimated the fraction of the repository experiencing seepage into the open drifts; • Overestimated seismic energy and rockfall; • Overestimated damage to the TADs due to seismic and rockfall events; • Overestimated the rate at which Alloy 22 will degrade; • Cladding performance was neglected; • Waste form alteration time was underestimated What did DOE do to make it think it needed Drip Shields?

11. Which is Cheaper, Faster, and Easier to Lower Dose Estimates for Disposal: • Additional work to remove conservatisms in dose estimates? • Drip shield example even saves money and time! • Introduce a major technological “fix” (e.g., fission-fusion hybrids)?

12. Several Benefits of Making Yucca Mountain Capacity Larger than the Current Legal Limit • Nuclear industry interested in building new plants • Opponents will point out there isn’t enough disposal space for existing plants • Delays or even eliminates the need for a second repository • Provides sufficient time buffer for introduction of advanced fuel cycles • R&D time to get closed fuel cycles into commercial operation: ~30-50 years

13. 0 Yucca Mountain Tuffs 41m 81m 20 m Yucca Mountain Capacity Options the EPRI Team Analyzed • Option 1: Expanded repository ‘footprint’ • Option2: Multi-level repository • Option 3: Grouped, single-level emplacement drifts • Determine the range in ‘expansion factor’ attributable to each option • Combinations of options

14. EPRI-Projected Yucca Mountain Technical Capacity is Much Higher Than the Legal Limit EPRI’s projected technical capacity range (~260,000-570,000 MTU, 4 to 9 times current legal limit) Current legal limit (63,000 MTU)

15. Feasibility of Direct Disposal of Dual-Purpose Canisters (DPCs, licensed for storage and transportation only) • Motivation: • Industry currently using DPCs • Avoids need to repackage • DPC capacity ~1.5x DOE’s Transportation, Aging, and Disposal canisters (TADs) • Considerations • DPC versus TAD diameter: it still fits • Added decay heat effects (hydrothermal, thermomechanical): Yucca Mountain can handle it • Post-closure dose: no effect • Criticality: still won’t happen

16. Need for Advanced Fuel Cycles for Waste Disposal Minimization? NO! • Yucca Mountain doses are already very low (<1% of background) • True for all other repository system estimates • Yucca Mountain technical capacity is big enough for decades to come • Why trade off near-term, certain increase in dose to lower very long-term hypothetical dose? • Need to compare source terms from the entire fuel cycle – not just what is headed to disposal • Which is cheaper and faster, introducing fission-fusion hybrids or doing some more work to eliminate conservatisms in disposal dose estimates? • “Radiotoxicity” is an inappropriate measure • Therefore, introduce advanced fuel cycle for reasons other than reducing waste disposal needs • Economics, resource utilization, energy independence, …

17. Yucca Mountain (and Most Other Repository Systems) can Help Keep our Options Open for Decades to Come • Use them as temporary storage until advanced fuel cycle(s) are ready • Co-locate storage, reprocessing, fuel fabrication, and disposal? • No need to move spent fuel twice if no nuclear advancement • Conclusion: Judicious use of repositories will support realistically-paced advanced fuel cycle development

18. Together…Shaping the Future of Electricity