Nuclear FusionNuclear FusionEnergy Energy

Rishi Gohil

ChE 379: Energy Technology and Policy

Dr. Thomas Edgar

Fall 2007

Nuclear Fusion PrincipleNuclear 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)

Nuclear FusionNuclear Fusion

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

Requirements for Fusion ReactionRequirements 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

Plasma Toroid (Tokamak)Plasma Toroid (Tokamak)

Flow of EnergyFlow of Energy

ChallengesChallenges

• 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.

AdvantagesAdvantages• 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.

JET (Joint European Torus)JET (Joint European Torus)• JET: World’s largest nuclear fusion

research facility

Fusion ReactorFusion 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.

Iter TimelineIter Timeline

ReferencesReferences• "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>