Nuclear Fusion - SAMI 2010

Introduction

• “Every time you look up at the sky, every one of those points of light is a reminder that fusion power is extractable from hydrogen and other light elements”

-Carl Sagan, 1991

Background

Fusion Basics

Nuclear Power

• Nuclear fission– Where heavy atoms,

such as uranium, are split apart releasing energy that holds the atom together

• Nuclear fusion– Where light atoms, such as

hydrogen, are joined together to release energy

The fuel of fusion

Even though the nuclear force is much stronger than the electromagnetic one, the RANGE of the nuclear one is much smaller.

Range of Electromagnetic force

Range of nuclear forcenucleus

These don’t get close enough to fuse together!

These get close enough to fuse together!

States of Matter

• Plasma is sometimes referred to as the fourth state of matter

Plasma Atoms

• In plasma the electrons are stripped away from the nucleus

• Like charges repel

– Examples of plasma on earth:

• Fluorescent lights

• Lightning

• Neon signs

Typical Plasmas

• Neon Signs• Thermonuclear

• Lightning• Fluorescent Lights

Plasma makes up the sun and the stars

Characteristics of Typical Plasmas

HOW FUSION REACTIONS WORK

P-P Fusion Reaction "P-P": Solar Fusion Chain

Inexhaustible Energy Supply

• Deuterium– Constitutes a small percentage of the hydrogen in water

• Separated by electrolysis• 1 barrel (42 gallons) water = ¾ oz. D = 32,000 gallons of oil

• Tritium– n + Li T + He– Lithium is plentiful

• Earth’s crust• Oceans

– Savannah, Georgia– Canada, Europe, Japan

D-T Fusion ReactionsD + T => He-4 + n

An enormous payoff

• The fraction of “lost” mass when H fuses into He is 38 parts out of 10,000

• This lost mass is converted into energy

• The energy released from 1 gram of DT = the energy from about 2400 gallons of oil

Energy-Releasing Reactions

Chemical Fission Fusion

Sample Reaction

C + O2 -> CO2 n + U-235 -> Ba-143 + Kr-91 + 2 n H-2 + H-3 -> He-4 + n

Typical Inputs (to Power Plant)

Bituminous Coal

UO2 (3% U-235 + 97% U-238) Deuterium & Lithium

Typical Reaction Temp. (K)

700 1000 108

Energy Released per kg of Fuel (J/kg)

3.3 x 107 2.1 x 1012 3.4 x 1014

E=mc2

• Einstein’s equation that equates energy and mass– E= energy– M= mass– C= speed of light (3 x 108 m/sec)

– Mass “lost “ in fusion is converted to energy

Plasma Confinement & Heating

Magnetic•Electromagnetic Waves

•Ohmic Heating (by electric currents)

•Neutral Particle Beams (atomic hydrogen)

•Compression (by magnetic fields)

•Fusion Reactions (primarily D+T)

Tokamak Schematic Laser-beam-driven Fusion

Inertial•Compression (implosion driven by laser or ion beams, or by X-rays from laser or ion beams)

•Fusion Reactions (primarily D+T)

Gravity•Compression (gravity)

•Fusion Reactions (such as the p-p chain)

Stars & Galaxies

Fusion By Magnetic Confinement

NOVA Machine- Inertial Confinement

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