# Presentation: 693932

## The Fission-Fusion Hybrid

- At last!
- A solution that has found a problem
- Jeff Freidberg MIT

## 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

## 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*

## 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

## 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

## 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

## 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

## Comparison of options

- What are the options for producing fissile fuel?

## 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

## 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