The Fission-Fusion Hybrid

1. TheFission-Fusion Hybrid At last! A solution that has found a problem Jeff Freidberg MIT

2. What problem are we trying to solve? • Future large demand for CO2-free base load electricity • May need 10 TW CO2-free electricity by mid-century • 20 times more CO2-free electricity than now • Only coal and nuclear fission are realistic options • Coal must solve the sequestration problem - tough job • Nuclear must solve waste and proliferation problems – plausible solutions exist • Nuclear must also solve the fuel supply problem – only 30 years of proven reserves at 10 TW level

3. What problem are we trying to solve? (con’t) • Mid-century uncertainties • Coal Sequestration • Discovery of new uranium • Prudent to have other options • Problem to be solved: Produce large amounts of fissile fuel so that fission becomes a sustainable source of electricity

4. How are we going to solve the problem? • Revisit an old idea Use a fission-fusion hybrid to produce fissile fuel • What has changed to make this old idea interesting? • We may need a lot more uranium than we thought • The fission community, at least at MIT, is interested and receptive to the idea

5. The fission-fusion energy park • One 200 MWe-equivalent (i.e. 500 MWt) tokamak fusion core • Surround with a thorium-lithium blanket – produces about 5500 kg of U-233 plus 20 kg of tritium per year • Separate the U-233 and combine it with U-238 to form fissile fuel for a LWR • This fuel is sufficient to power two 800 MWe LWRs • Power gain = 8! • Burn the resulting Pu and actinides in an onsite 300 MWe fast reactor. • Store short lived radioactive byproducts on site • Transmute long lived radioactive byproducts in the hybrid blanket

6. Why is this good for fusion • How can fusion make a contribution by mid-century? • Fusion electricity is tough from a plasma physics and fusion engineering point of view • Fissile fuel from fusion is much easier • Need Q = 2 -5 for success rather than Q = 50 for electricity • Do not need steady state or ultra-high availability • Even if fusion electricity is successful, it will likely cost more than a comparable fission reactor • What about tainting fusion with fission? If we can help fission produce electricity we must do so and not be dilettantes posturing in the wind

7. Why is this good for fission? • The fission-fusion hybrid converts fission energy from an intermediate stop-gap energy source into one that is sustainable for over 10,000 years • Making fissile fuel from a fission-fusion hybrid may be better than alternate options

8. Comparison of options • What are the options for producing fissile fuel?

9. From ITER to a fission-fusion DEMO • Plasma physics • MHD, transport, heating OK • Divertor and first wall scale-up problems remain • Current drive may not be necessary • Larger B field very desirable for plasma physics • Fusion engineering • Materials for the first wall and divertor • Tritium and fissile fuel breeding • Increased neutron fluence • Increased availability

10. Recommendations for OFES • Initiate a 2 year pre-ARIES scoping study on the fission-fusion hybrid system • Increase emphasis on the first wall and divertor problems • Initiate a superconducting magnet R&D program to make higher field magnets