Nuclear physics

1. Nuclear Fusion
Energy
Rishi Gohil
ChE 379: Energy Technology and Policy
Dr. Thomas Edgar
Fall 2007

2. Nuclear Fusion Principle
• Energy generated by joining two elements with
low atomic numbers.
• Most efficient reaction known is fusion of
Hydrogen isotopes, Deuterium and Tritium, to
form Helium.
• Fusion is source of energy for stars and the Sun.
• High temperatures > 100 million degrees Kelvin
needed for fusion on earth
• At high temperature, the gas mixture forms a
plasma (hot, electrically charged gas)

3. Nuclear Fusion
• This reaction releases 17.6 MeV of
energy. No limit on amount of fusion that
can occur (unlike fission).

4. Requirements for Fusion Reaction
• Plasma Temperature:100-200 million Kelvin
– Needed to overcome natural positive repulsive forces
of plasma ions
• Energy Confinement Time: 4-6 seconds
– The Energy Confinement Time is a measure of how
long the energy in the plasma is retained before being
lost.
• Central Density in Plasma:1-2 x 1020 particles m-
3
– Large density needed because number of fusion
reactions per unit volume is roughly proportional to
the square of the density

5. Plasma Toroid (Tokamak)

6. Flow of Energy

7. Challenges
• Current research in controlling high
temperature plasma
– How to heat plasma to >100 million deg C.
– How to confine such a plasma
– How to sustain the reactions.

8. Advantages
• Abundant fuels: Deuterium (from water),
Tritium (from Lithium) and Lithium (plentiful
on Earth’s crust).
• Inherently safe: Because conditions for
reaction are stringent and small amounts
of fuel used
• Environmentally safe: No greenhouse gas
emissions and byproduct of reaction is
Helium.

9. JET (Joint European Torus)
• JET: World’s largest nuclear fusion
research facility

10. Fusion Reactor
• EU to build pilot fusion reactor, Iter.
– Cost: 4.57 Billion EURO (2000 prices) over 10 yrs
– Life: 35 years
– Countries Involved: 7
– Design: reactions occur in 100 million degree gas (plasma)
suspended in donut shaped magnetic field.
– Problems: Sustained and stable reactions
– Potential: 500 MW output from 70 MW power input during
pulses of at least 400 secs.
– If technology works commercial reactor, Demo, will be built.
– Advantages: No greenhouse emissions, inherently safe due to
malfunction shutdown systems, no high-level long-lived
radioactive waste produced.

11. Iter Timeline

12. References
• "Nuclear Fusion 'Put to the Test'" BBC NEWS 17 Feb. 2005. 19 Nov. 2007
<http://news.bbc.co.uk/2/low/science/nature/4270297.stm>.
• “Fusion Power." United Kingdom Atomic Energy Authority. 20 Nov. 2007.
<http://www.fusion.org.uk/>.
• "JET." EFDA. 20 Nov. 2007. <http://www.jet.efda.org/index.html>.
• “Nuclear Fusion” howstuffworks.19 Nov 2007. Craig Freudenrich, Ph.D.
<http://science.howstuffworks.com/fusion-reactor3.htm>