Energy Systems & Sustainability Freshman Seminar 2013 Mayda M. Velasco Oct. 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 ChemicalFissionFusion Sample Reaction C + O 2  CO 2 n U  143 Ba + 91 Kr + 2 n 2 H + 3 H  4 He + n Typical Inputs (to Power Plant) Bituminous CoalUO 2 (3% 235 U+ 97% 238 U)Deuterium & Lithium Typical Reaction Temp. (K) Energy Released per kg of Fuel (J/kg) 3.3 x x x 10 14

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  Radioactive waste

Nuclear Binding Energy Fusion favored Fission favored

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 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  4 He + 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 Waste Coal 10,000 (ashes) 0 Fission Fusion: Today’s Materials Advanced Materials

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 45