Modern Physics Part 2 COMPLETE

Z value for radioactivity

Z > 83

Goal of radioactive isotopes

Stability

Types of nuclear decay

Alpha, Beta, Gamma, and Neutron radiation.

How isotopes achieve stability

They spontaneously emit mass and energy to achieve stability.

Alpha particle composition

Two protons and two neutrons. It is identical to a helium nucleus.

Effect of alpha particle on nuclear structure

Yes.

Most massive form of radiation

Alpha particle.

Stopping alpha particles

Because of its large mass, it can be stopped by paper.

Danger of alpha particles to humans

Yes they are dangerous to humans. They ionize critical biological functions such as DNA Replication.

Radioactive particle with highest electrical charge

The alpha particle.

Direction of alpha particle movement

Down.

Second most massive form of radiation

Beta radiation.

Antimatter counterpart to the electron

Positron, identical to the electron except for electrical charge, which it has a charge of +1.

What the positron does

Immediately after creation, it annihilates the electron, leaving only photons behind.

Particles gamma radiation accompanies

Alpha radiation and Beta negative radiation.

Radiation associated with antineutrinos

Beta negative.

Radiation associated with neutrinos

Beta positive.

When beta negative decay occurs

Occurs when a nucleus has too many neutrons compared to number of protons.

Neutron behavior in beta negative decay

Due to weak force interaction, it becomes a proton.

Effect of beta negative decay on an element

It moves it up the periodic table.

Occurrence of beta positive decay

It occurs when a nucleus has too many protons.

Proton behavior in beta positive decay

It turns into a neutron, because of weak force interaction.

Effect of beta positive decay on an element

It moves down the periodic table due to the loss of a proton.

When gamma radiation occurs

It occurs after an excited nucleus returns to ground state.

Definition of gamma radiation

Electromagnetic radiation of extremely high frequency.

Gamma radiation interaction with matter

It rarely does, to even stop it you would need several centimeters of dense material like lead or concrete.

Effect of gamma particles on DNA structure

No.

Decay constant

It is the probability of decay of a nucleus per second, and is unique to that particular nuclide. It is also exponential.

SI Unit for radioactive activity

The bequerel, and it measures one decay per second.

Definition of half-life

It is the time for 1/2 a substance to decay.

Duration of decay

Until a stable configuration is reached.

Exoergic Reactions

Exothermic reactions, occur when relatively little energy is introduced compared to the amount of energy produced.

Endoergic Reaction

Require great amounts of energy; more is put in than produced.

Threshold Energy

The minimum amount of kinetic energy needed to initiate an endoergic reaction.

Fission for elements heavier than iron

For elements heavier than iron, fission is exothermic.

Fission for elements lighter than iron

For elements lighter than iron, fission is endoergic.

Forces in fission

The electromagnetic force overpowers the strong force.

Induction of fission

Through introduction of neutrons into the nucleus.

Effect of neutron introduction into the nucleus

Because the strong force can't handle that many neutrons, it bursts.

Products of fission

Daughter Particles.

Weight comparison of fission products to parent particle

Lighter.

Behavior of free neutrons during fission

They are emitted, and may cause other fission events. This is the main element of chain reactions.

Inducing fission

Fission bombardment.

Minimum mass for chain reaction

Critical Mass.

K value measurement

The average number of neutrons from each fission event that will create another fission event.

K Value less than 1

It means it is subcritical, and no reaction exists.

K Value equal to one

It produces one neutron that can create another event. The material is critical.

K Value greater than 1

More than one neutron can cause another fission event, and the mass is supercritical.

Nuclear weapons K Value

The material needs to be supercritical.

Examples of fissionable fuels

Uranium - 235, natural uranium needs to be enriched for nuclear applications; Plutonium 239, which is not naturally occurring and is made from Uranium 238.

Neutrons produced by Plutonium 239

Plutonium 239 also makes 2.9 neutrons per event.

Fusion with elements lighter than iron

Exothermic.

Fusion with elements heavier than iron

Endoergic.

Energy source in fusion and fission

The mass defect.

Mass defect

The difference between the theoretical mass of adding two elements together and the actual observed mass.

Mass defect in fission and fusion

Given off as Kinetic Energy.

Where fusion naturally occurs

In stars, and the sun.

Thermonuclear weapons

Use fusion.

Spontaneous fission

Yes, but it is quite rare.

Requirements for fusion

Temperatures that exceed 10^8K (179,999,540 degrees F).

Challenges of fusion

You can't create a chain reaction with fusion.

Thermonuclear process

Nuclei fuse together, heavier nuclides are created, subatomic particles are emitted (beta particles, neutrinos, protons, gamma radiation), and then kinetic energy is emitted.

Common fuels for fusion

Protium, Deuterium, and Tritium, all of which are hydrogen based.

Nuclear Reactor

Essentially a steam engine.

Components of the Nuclear Reactor

Fuel rods, Coolant, Control Rods, Moderator, Turbine, Generator.

Function of fuel rods

Pellets are filled into rods & the rods are grouped into bundles. Rods are made of Zirconium.

Coolant in a reactor

Removes the heat produced by fission reactions, flows between fuel rods.

Control Rods

These control the speed of the reactions, controlled by inserting or withdrawing control rods made of elements that are good absorbers of neutrons.

Moderator

Slows down fast neutrons and prevents them from leaving the reactor core.

Why water is used as a moderator

Because it has a built in safety factor; once water runs out the K factor cannot achieve criticality.

Neutron Poisoning

Undesirable absorption of neutrons in a reactor core; causes less efficiency as something absorbs the neutrons and doesn't do anything with it.

Thermal neutrons

The slowed down neutrons that occur when they bounce off the moderator.

Heavy Water Reactors

Canada uses this, and heavy water is more effective than light water at slowing down the neutrons.

Light Water Reactor

United States uses these reactors, because it is cheaper.

Turbine in a reactor

Heat engines, subject to the second law of thermodynamics.

Generator in a reactor

Turns the steam power into electrical power.

Principle of Operation of reactors

The fission releases energy and converts it to heat from the fuel rods, then is converted into steam from the water system.

Breeder Reactors

Reactors that make more fissile material than they consume.

Leftover material from the reactor

Remaining U - 238 is sent to a reprocessing plant or stored at waste, or bombards U - 238 with neutrons creating Pu 239.

Methods of creating a nuclear explosion

Gun Assembly and Implosion.

Gun assembly

When two or more pieces of fissile material are brought together rapidly to form one piece that exceeds the critical mass.

Implosion

When you compress a subcritical quantity of a specific isotope of uranium or plutonium, it can become critical or supercritical.

Thermonuclear Weapons

Uses thermonuclear fusion (Needs temperatures from tens of millions of degrees).

Underwater Burst

Center of a nuclear explosion is beneath water

Underground Burst

Center of a nuclear explosion is beneath the ground

Surface Burst

Explosion occurs at or slightly above the surface of land or water

Air Burst

Moderately high altitude, fission products dispersed into the atmosphere

High altitude Burst

Explosion occurs higher than 100,000 feet

Explosion Phenomena

Rapid energy release; Temperature increases to millions; Pressure increases to millions; Ionization; Fireball (X-Ray)

Double-Pulse

Fireball overtakes shockwave

Blast/Shock

50% of energy in an Airburst

Thermal Radiation

35% of energy from an Airburst

Initial Nuclear Radiation

5% of total fission energy, released within first 60 seconds

Residual Nuclear Radiation

10% of total fission energy, emitted after first 60 seconds

Gamma Rays

Travels long distances through air and can penetrate thick materials

X-Rays

Formed by high energy electron interactions

Neutron Radiation

Comes from nuclear fuels, absorption can cause atoms to become unstable

Alpha Radiation

Created by unspent nuclear fuels and unstable isotopes from detonations

Beta Radiation

Comes from fission products in a nuclear event

Scanning electron microscope

Higher magnification and resolution than conventional