Nuclear Reactions:

AN INTRODUCTION TO

FISSION, FUSION, AND

NUCLEAR POWER

AN INTRODUCTION TO

FISSION, FUSION, AND

NUCLEAR POWER

Nuclear reactions deal with interactions Nuclear reactions deal with interactions between the nuclei of atomsbetween the nuclei of atoms

The focus of this presentation are the The focus of this presentation are the processes of nuclear fission and nuclear processes of nuclear fission and nuclear fusionfusion

Both fission and fusion processes deal with Both fission and fusion processes deal with matter and energymatter and energy

Introduction

Matter and Energy

Previous studies have taught us that “matter Previous studies have taught us that “matter and energy cannot be created nor destroyed”and energy cannot be created nor destroyed”

We now need to understand that Matter and We now need to understand that Matter and Energy are two forms of the same thingEnergy are two forms of the same thing

Matter can be changed into EnergyMatter can be changed into Energy

Einstein’s formula above tells us how the Einstein’s formula above tells us how the change occurschange occurs

In the equation above:In the equation above:E = EnergyE = Energym = Massm = Massc = Speed of Light (Universal Constant)c = Speed of Light (Universal Constant)

E = mc2

E = mc2

The equation may be read as follows:The equation may be read as follows:

Energy (E) is equal to Mass (m) multiplied Energy (E) is equal to Mass (m) multiplied by the Speed of Light (c) squaredby the Speed of Light (c) squared

This tells us that a This tells us that a small amount of mass can small amount of mass can be converted into a very largebe converted into a very large amount of amount of energyenergy because the speed of light (c) is an because the speed of light (c) is an extremely large numberextremely large number

Fission notes

Fission may be defined as the process of Fission may be defined as the process of splitting an atomic nucleus into fission splitting an atomic nucleus into fission fragmentsfragments

The fission fragments are generally in the form The fission fragments are generally in the form of smaller atomic nuclei and neutronsof smaller atomic nuclei and neutrons

Large amounts of energy are produced by the Large amounts of energy are produced by the fission processfission process

Fission notes

Fissile nuclei are generally Fissile nuclei are generally heavy atoms with heavy atoms with large numbers of nucleonslarge numbers of nucleons

The nuclei of such heavy atoms are struck by The nuclei of such heavy atoms are struck by neutrons initiating the fission processneutrons initiating the fission process

Fission occurs due to electrostatic repulsion Fission occurs due to electrostatic repulsion created by large numbers of protons within the created by large numbers of protons within the nuclei of heavy atomsnuclei of heavy atoms

A classic example of a fission reaction is that of A classic example of a fission reaction is that of U-235:U-235:

U-235 + 1 Neutron U-235 + 1 Neutron

2 Neutrons + Kr-92 + Ba-142 + Energy2 Neutrons + Kr-92 + Ba-142 + Energy In this example, a stray neutron strikes an atom of U-235. In this example, a stray neutron strikes an atom of U-235.

It absorbs the neutron and becomes an unstable atom of It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission. Notice that more U-236. It then undergoes fission. Notice that more neutrons are released in the reaction. These neutrons neutrons are released in the reaction. These neutrons can strike other U-235 atoms to initiate their fission.can strike other U-235 atoms to initiate their fission.

Fission notes

Fission notes

The fission process is a natural one. A French The fission process is a natural one. A French researcher found a natural uranium reactor in researcher found a natural uranium reactor in Gabon, West Africa; it has been estimated to Gabon, West Africa; it has been estimated to be over 2 billion years oldbe over 2 billion years old

Fission produces large amounts of heat energy Fission produces large amounts of heat energy and it is this heat that is captured by nuclear and it is this heat that is captured by nuclear power plants to produce electricitypower plants to produce electricity

Fusion is a nuclear reaction whereby Fusion is a nuclear reaction whereby two light two light atomic nuclei fuse or combine to form a single atomic nuclei fuse or combine to form a single larger, heavier nucleuslarger, heavier nucleus

The fusion process generates tremendous The fusion process generates tremendous amounts of energy; refer back to Einstein’s amounts of energy; refer back to Einstein’s equationequation

For fusion to occur, a large amount of energy For fusion to occur, a large amount of energy is needed to overcome the electrical charges is needed to overcome the electrical charges of the nuclei and fuse them togetherof the nuclei and fuse them together

Fusion notes

Fusion notes

Fusion reactions do not occur naturally Fusion reactions do not occur naturally on our planet but are the principal type on our planet but are the principal type of reaction found in starsof reaction found in stars

The large masses, densities, and high The large masses, densities, and high temperatures of stars provide the initial temperatures of stars provide the initial energies needed to fuel fusion energies needed to fuel fusion reactionsreactions

The sun fuses hydrogen atoms to The sun fuses hydrogen atoms to produce helium, subatomic particles, produce helium, subatomic particles, and vast amounts of energyand vast amounts of energy

Mass and Energy are two forms of the same Mass and Energy are two forms of the same thing; neither can be created nor destroyed but thing; neither can be created nor destroyed but mass can be converted into energy (E = mcmass can be converted into energy (E = mc22))

Fission is a nuclear reaction in which a heavy Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nucleiatomic nucleus is split into lighter atomic nuclei

Fusion is a nuclear reaction in which 2 light Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, atomic nuclei are combined into a single, heavier atomic nucleusheavier atomic nucleus

Review notes

Nuclear reaction notes

Chain reaction occurs when a Uranium atom splits

Different reactions

– Atomic Bomb in a split second

– Nuclear Power Reactor more controlled, cannot explode like a bomb

History of nuclear power

1938– Scientists study Uranium nucleus

1941 – Manhattan Project begins

1942 – Controlled nuclear chain reaction

1945 – U.S. uses two atomic bombs on Japan

1949 – Soviets develop atomic bomb

1952 – U.S. tests hydrogen bomb

1955 – First U.S. nuclear submarine

“Atoms for Peace”

Program to justify nuclear technology

Proposals for power, canal-building, exports

First commercial power plant, England 1956

The energy in one pound of highly enriched Uranium is comparable to that of one million gallons of gasoline.

One million times as much energy in one pound of Uranium as in one pound of coal.

Economic advantages notes

Emissions Free notes

Nuclear energy annually prevents

– 5.1 million tons of sulfur

– 2.4 million tons of nitrogen oxide

– 164 metric tons of carbon

Nuclear often pitted against fossil fuels

– Some coal contains radioactivity

– Nuclear plants have released low-level radiation

Nuclear Power Plants

Nuclear power around the globe

17% of world’s electricity from nuclear power

– U.S. about 20% (2nd largest source)

431 nuclear plants in 31 countries

– 103 of them in the U.S.

– Built none since 1970s (Wisconsin as leader).

– U.S. firms have exported nukes.

– Push from Bush/Cheney for new nukes.

Countries Generating Nuclear Power

Country Total MW

USA 99,784

France 58,493

Japan 38,875

Germany 22,657

Russia 19,843

Canada 15,755

Ukraine 12,679

United Kingdom 11,720

Sweden 10,002

South Korea 8,170

Technology depends on operators

Nuclear Reactor Process

3% enriched Uranium pellets formed into rods, which are formed into bundles

Bundles submerged in water coolant inside pressure vessel, with control rods.

Bundles must be SUPERCRITICAL; will overheat

and melt if no control rods. Reaction converts water to steam, which powers steam turbine

Nuclear Reactor Structure

Reactor’s pressure vessel typically housed in 8” of steel

36” concrete shielding

45” steel reinforced concrete

Back end: Radioactive waste

Low-level wastes in commercial facilities

Spent fuel in pools or “dry casks” by plants

Nuclear lab wastes

– Hanford wastes leaked radiation into Columbia River

High-level underground repository

– Yucca Mountain in Nevada to 2037

– Wolf River Batholith in Wisconsin after 2037?

– Risks of cracks in bedrock, water seepage

Yucca Mountain

Radioactive Waste Recycling

Disposal of radioactive waste from nuclear power plants and weapons facilities by recycling it into household products.

In 1996, 15,000 tons of metal were received by the Association of Radioactive Metal Recyclers . Much was recycled into products without consumer knowledge.

Depleted Uranium munitions for military.

Nuclear energy has no typical pollutants or greenhouse gasses

Nuclear waste contains high levels of radioactive waste, which are active for hundreds of thousands of years.

The controversy around nuclear energy stems from all parts of the nuclear chain.

Summary notes