James J. Laidler Chemical Technology Division Argonne National Laboratory

1. Separations TechnologyDevelopment James J. Laidler Chemical Technology Division Argonne National Laboratory

2. Accumulation of Spent Nuclear Fuel in the United States • Presently there are 103 commercial nuclear power stations operating in the U.S. • Over 2,000 tonnes of spent fuel is generated each year • Most of the fuel is in storage at the reactor sites, some at Independent Spent Fuel Storage Installations (ISFSIs) such as the GE Morris plant • Over half of the utility sites are at full capacity in their storage pools • By 2015, the U.S. spent nuclear fuel inventory will exceed 87,000 tonnes

3. Composition of Spent Nuclear Fuel Contents of 1 tonne (~ 2 fuel assemblies) after cooling for 40 years: Fission Products: 10.1 kg Lanthanides 0.5 kg 137Cs 0.2 kg 129I 0.8 kg 99Tc 0.006 kg 79Se 0.3 kg 135Cs 3.4 kg Mo isotopes 2.2 kg Ru isotopes 0.4 kg Rh isotopes 1.4 kg Pd isotopes 955.4 kg U 7.8 kg Pu (5.1 kg 239Pu) 0.6 kg 237Np 1.6 kg Am 0.02 kg Cm 34.7 kg fission products

4. Incentives forPartitioning and Transmutation • Reduce radiotoxicity of high-level waste to be disposed in a geologic repository • Elimination of 99.9% of the actinides reduces the radiotoxicity by a factor of 100,000 compared to direct disposal of spent fuel • Reduce health effects from uranium mining/milling • Make use of the energy potential in the fissionable isotopes present in spent fuel • Transuranic elements present in 80,000 tonnes of spent nuclear fuel can fuel all of the present U.S. reactors for over 20 years • Eliminate a source of weapons material • No weapons plutonium sent to repository storage • Eliminate safety uncertainties related to repository disposal • Reduce time frame of concern to <1,000 years (within realm of recorded human experience) • Reduce costs of geologic disposal • Place wastes in more durable waste forms (e.g., ceramics) • No need for active cooling

5. Transmutation Reactions • Transuranic elements (Np, Pu, Am, Cm): fission • Iodine: 129I53 + 1n0130I53130Xe54 + β- • \ • Technetium: 99Tc43 + 1n0 100Tc43100Ru44 + β- (12.4h) (stable) 23Na11 + 1n0 24Na11  24Mg12 + β- (15h) (stable) (15.8s) (stable)

6. ATW Separations System: Certain Constraints Apply to Technology Selection • Different fuels, different characteristics • LWR spent fuel • Oxide fuel, zircaloy-clad; cooled for 7-10 years • Low fissile content • Large throughput required, ~1,500-2,000 MTHM/y (total system) • Transmuter blanket fuel recycle • Inert matrix fuel (probably Zr matrix); cooled for only two years • Fissile content could be on the order of 15% at discharge • Low throughput, ~35-50 MTHM/y (total system) • Desire to remove uranium as low-level waste or in a form that can be stored on the surface without shielding • Likelihood of emergence of multi-tier system as the preferred path forward

7. Reference Separations Process • Aqueous process for treatment of LWR spent fuel • Pyrochemical process for treatment of ATW fuel • Stringent recovery targets to ensure realization of full benefits to repository disposal • 99.9% recovery of transuranics • 95% recovery of technetium and iodine • 99.9% recovery of uranium, as Class C low-level waste • Currently subject of detailed trade study • Alternative processes being considered, but reference system has received broad endorsement (domestic and foreign)

8. Overall Chemical Separations Scheme for AAA Program

9. Future Multi-Strata Nuclear Systems • U.S. program for transmutation of nuclear wastes is founded on a recovery efficiency of 99.9% for the transuranic elements present in spent fuel and the fissioning of at least 99.5% of these transuranics • In the multi-strata nuclear systems considered for future deployment, existing or advanced light water reactors will make up a large fraction of the nuclear generating capacity for several decades • The spent fuel from these LWRs will be processed to burn plutonium (and perhaps the minor actinides) in a critical reactor operated to generate electricity (“first tier”)

10. A Multi-Strata System • TIER 0 – Commercial Reactors • Existing and future reactors, electricity generation mission • Uranium-based fuels • Once-through fuel cycle, potential for Pu recycle • TIER 1 – Plutonium Burner Reactors • Efficient Pu-239 burners, electricity generation mission • Non-fertile fuel, very high burnup • Once through fuel cycle • TIER 2 – Minor Actinide Burner Reactors • Fast spectrum reactors, liquid metal cooling • Electricity generation mission • Critical or subcritical (accelerator-driven) • Multi-recycle fuel cycle for minor actinide destruction

11. Future Multi-Strata Nuclear Systems (continued) • The first-tier reactor will be one that is selected by U.S. utilities for deployment; it could be an advanced LWR, a gas-cooled reactor, or a fast reactor • The inherent safety characteristics of the gas-cooled reactor, together with its high thermal efficiency, make it a strong candidate for the first-tier system • It is foreseen that the gas-cooled reactor would operate as a once-through system with very high fuel burnup, to eliminate the need for fuel recycle • The unburned transuranics remaining after discharge from the first-tier reactor would be sent to a fast spectrum system, either critical or accelerator-driven, for burning in a multi-recycle mode

12. A Possible “Multi-Tier” Concept

13. TRISO Particles Allow Deep Burnup in Once-Through Mode  Pyrolytic Carbon TRISO Coating Silicon Carbide Porous Carbon Buffer Plutonium Oxide (PuO1.68) Particle diameter: 650-800 μm PARTICLES COMPACTS FUEL ELEMENTS

14. Pu Particles Achieved High Transmutation Levels in Peach Bottom I Reactor Pu Oxide Th - Pu Oxide 747,000 MW-days/tonne >95% 239Pu & >65% all Pu Transmuted 183,000 MW-days/tonne >95% 239Pu Transmuted

15. Candidate Tier 2 Transmuter Fuel Types • Requirement: • Inert matrix, non-fertile (uranium-free) fuel • Reliable operation to burnups of 15-30 atom % • Choice depends on: • Burnup capability • Coolant compatibility • Fabricability • Likely candidates: met-met, cer-met, cer-cer • Dispersion of TRU-Zr metal alloy in Zr metal matrix • Dispersion of TRU-Zr nitride in Zr nitride matrix • Dispersion of TRU oxides in Zr metal matrix • Dispersion of TRU oxides in stainless steel or molybdenum matrix • Dispersion of TRU oxides in ceramic matrix

16. Overall Chemical Separations Scheme

17. Criteria: LWR Fuel Treatment • Extraction of 99.9% of uranium at DF of 106 • Extraction of 95% of Tc and I in form amenable to target fabrication • Extraction of TRUs and conversion to metallic form with 99.9% recovery • Minimization of high-level liquid waste generation • Capability for high-throughput operation, 200 MTHM per year

18. LWR Fuel Separations Processing

19. The PUREX Process • PUREX is an aqueous solvent extraction process used to separate and purify U and Pu from dissolved spent fuel • 1st cycle: U and Pu are extracted into the organic solvent (TBP, tributyl phosphate) and the fission products and other actinides remain in the aqueous waste stream (“raffinate”) • Stripping step: U and Pu are stripped from the solvent separately • 2nd and 3rd cycles: U and Pu are re-extracted to achieve the required purification • Tc resides primarily in the raffinate, but is also a contaminant in both the U and Pu streams

20. PUREX Plant at Hanford 1,080 ft.

21. COGEMA Plant at LaHague (France)