Energy Systems & Energy Systems & SustainabilitySustainability

Freshman Seminar 2013Mayda M. VelascoMayda M. Velasco

Oct. 1, 2013Oct. 1, 2013

Few comments about...Nuclear Fusion

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

Our Sun

Fusion Advantages• Abundant fuel, available to all nations

– Deuterium and lithium easily available for thousands of years• Environmental Advantages

– No carbon emissions, short-lived radioactivity• Modest land usage

– Compact relative to solar, wind and biomass• Can’t blow up

– Resistant to terrorist attack– Less than 5 minutes of fuel in the chamber

• Not subject to daily, seasonal or regional weather variation– No large-scale energy storage nor long-distance transmission

• Can produce electricity and hydrogen– Compliments other nearer-term energy sources

Fusion Disadvantages

• Huge research and development costs• Radioactivity

Background

Fusion Basics

Energy-Releasing Reactions

Chemical Fission Fusion

Sample Reaction

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

Typical Inputs

(to Power Plant)

Bituminous Coal UO2 (3% 235 U+ 97% 238U) 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

What is an atom?

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

Fusion process

Stability Band – Lifetime

Radioactivewaste

Nuclear Binding EnergyFu

sion

favo

red

Fissionfavored

States of Matter

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

Plasma makes up the sun and the stars

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

Other Typical Plasmas

• Interstellar• Solar Corona• Thermonuclear

• Laser

Characteristics of Typical Plasmas

Basic Characteristics

• Particles are charged• Conducts electricity• Can be constrained magnetically

Fusion Fuel

• Tritium

• Deuterium

The fuel of fusion

Inexhaustible Energy Supply• Deuterium– Constitutes a small percentage of the hydrogen

in water• Separated by electrolysis• 1 barrel (42 gallons) water ¾ oz.

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

• Earth’s crust• Oceans

– Savannah, Georgia– Canada, Europe, Japan

Fusion Fuel: Deuterium

Other Possible Fusion Fuels:

Helium-3 Nuclear Fusion

Proton Proton NeutronProton

Where is Helium-3?

• Helium-3 comes to us from the sun on the solar wind

• It cannot penetrate the magnetic field around the earth, so it eventually lands on the moon

• One shuttle load- 25 tons- would supply the U.S. with enough fuel for one year

HOW FUSION REACTIONS WORK?

Two Main Types of Fusion Reactions: #1 = Proton-Proton

"P-P": Solar Fusion Chain

Two Main Types of Fusion Reactions: #2 = D-T

D + T 4He + n

More on Fusion Reactions

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

The result

• Inexhaustible fuel source– Seawater & Lithium

• The MOST “bang for your buck”• Inexpensive to produce• Widely distributed fuel source– No wars

• No pollution– Helium is not polluting

• Fuel that is non-radioactive– Residue Helium-4 is non-radioactive

• Waste reduction

More of Fusion Radioactivity

• Stray Tritium– Relatively benign

• Doesn’t emit strong radioactivity when it decays– So only dangerous when ingested or inhaled

• Shows up in one’s body as water– Easily and frequently flushed out

• Half-life of 12 years– No long-term waste problem– Won’t decay while in one’s body

– Less than natural exposure to radon, cosmic rays and much less than man-made x-rays

More on Fusion Radioactivity

• Reactor Structure– Development of special “low-activation” structural

materials• Vanadium• Silicon-carbide

– Wait ten to fifteen years after shutdown• The reactor will be less radioactive than some natural

materials (particularly uranium ores)• Recycle into a new fusion reactor

Waste Reduction

Power Source Total Waste (m3) High-Level RAD WastePower Source Total Waste (m3) High-Level RAD WasteCoalCoal 10,000 (ashes) 10,000 (ashes) 0 0

FissionFission 440 440 120 120

Fusion:Fusion:Today’s MaterialsToday’s Materials 2000 2000 30 30Advanced MaterialsAdvanced Materials 2000 2000 0 0

So why aren’t fusion plants already in operation?

How fusion works and the obstacles in the way

The Problems

• Harnessing the Energy• Achieving & sustaining high temperatures– The reaction takes place at a temperature hotter

than the surface of the sun– 0.1 seconds

• Containing the fuel & the reaction• Money for research and development

Harnessing the Energy

Achieving ignition temperatures

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