nuclear energy chapter 15. radioactivity 15.1 remember: atoms are made of protons, neutrons, and...

Nuclear Energy

Chapter 15

RADIOACTIVITY15.1

Remember:

Atoms are made of protons, neutrons, and electrons

Most atoms are stable

They have a correct

balance of protons and

neutrons.

Other atoms are unstable

They have an “off-balance”

number of protons and

neutrons.

radioactive

Atoms whose nuclei are unstable are said to be

Eventually, these atoms breakdown.

The process is called “radioactivity”.

Radioactivity is not new.

Radioactivity is not caused by man.

Radioactive decay in Earth’s

interior heats the water for

geysers

Radioactive decay in Earth’s interior heats the water for hot springs

Most of the radiation we

encounter

Nuclear Technology - Pros

• Medical X-rays & Anti Cancer Treatments

Nuclear Technology - Pros

• Smoke detectors

Nuclear Technology - Pros

• Nuclear Energy

Nuclear Technology - Cons

• Nuclear Disaster

Nuclear Technology - Cons

• Nuclear Weapons

Nuclear Technology - Cons

• Nuclear Weapons

Nuclear Technology Demands Responsibility

• Safeguard nuclear material• Safe, clean disposal• Protect the environment for

future generations

It’s up to you to make the

decisions for the future!

Alpha, Beta, and Gamma Rays

Chapter 15.2

Radioactive elements emit 3 different types of particles

alphabeta

gamma

αβ

γ

α particles are positively charged

β particles are negatively charged

γ particles are neutral

• http://www.youtube.com/watch?v=o-9yt7OAYmE

α particles are He nuclei

α particles are Helium nuclei

α particles• Relatively low speed• Eventually become

HE• Easy to shield against• Can’t go through

paper or clothing

β particles are electrons

• Neutrons “decay”• Produce a proton and

electron

β particles

• Faster than α particles• Can penetrate paper and clothes• Can penetrate and damage skin• Can not penetrate denser material like aluminum

γ (gamma) rays are pure energy

• Gamma rays have more energy than visible light, UV light or X-rays

γ (gamma) rays• Can easily

penetrate and damage living tissue

• Can penetrate most materials – except lead

Let’s Compare

PenetratingPower

γ (gamma) rays can help preserve food

Question

• Pretend you are given three radioactive rocks.

• One is an alpha emitter, one is a beta emitter and one is a gamma emitter and you know which is which.

Question

• You can throw one away.

• Of the other two, you must hold one in your hand and place one in your shirt pocket.

Question

• What can you do to minimize your exposure?

Answer

• Hold the alpha emitter in your hand.

• The skin on your hand will shield you.

Answer

• Put the beta emitter in your pocket.

• The combined thickness of you skin and clothing should shield you from the beta emissions.

Answer

• THROW AWAY THE GAMMA EMITTER!

• Because it would penetrate your body from any of these locations.

Answer

• In a perfect world……

• Distance yourself from all the rocks!.

Environmental Radiation

Chapter 15.3

Most radiation we encounter originates in nature

• Common rocks and minerals

Which family is exposed to more radiation?

The one living in a Brick house?

Or the one living in a wooden house?

• More radiation exposure

• Naturally Occurring

RadonA Common Source

of Radiation

• Radon

• Heavy, inert gas• Arises from uranium deposits

Is Radon Dangerous?

• According to the EPA, radon is the second leading cause of lung cancer.

• It is the leading cause of lung cancer in non-smokers.

How radon produces cancer

Levels vary with geology

You can check radon levels with a

test kit

High levels require action

Here’s another interesting question….

Which is a greater source of radiation?

Coal Combustion Nuclear power

The Coal Industry!

• Global combustion of coal releases about 13,000 tons of radioactive thorium and uranium into the atmosphere.

• In addition to other polluting molecules released into the air.

• Worldwide they generate about 10,000 tons of radioactive waste each year

• Almost all the waste is contained and not released into the atmosphere.

Nuclear plants

RADIATION DAMAGE TO THE BODY

Remember

• Most of the radiation we receive is from natural sources and medical procedures

The human body itself is a source of radiation!

The radiation comes from the potassium we eat.

Our bodies contain about 200 mg K

≈ 180 mgother Kisotopes

≈ 20 mg K40

*radioactive*

β emitter

Between every heartbeat…

≈ 5000 K40 undergo spontaneousradioactive decay!

Radiation is everywhere!

Radiation can cause damage to cells

Radiation can cause serious burns and hair loss

Cells can repair radiation damage if it is not too severe

Radiation can damage DNA

Radiation can damage DNA resulting in cancer

High doses of radiation can damage DNA resulting hereditary

birth defects

Common sense

• Avoid radiation when possible

• All radiation can not be avoided

• Most is simply part of nature

HALF- LIFEChapter 15.5

Radioactive isotopes decay at different rates

• Measured in terms of a characteristic time

• “Half-life”

Half-life

The time needed for half the radioactive atoms of a radioactive

material to decay

Radium (Ra 226)

• Half life = 1620 years

Half lives are constant

• Not affected by external conditions• Some are less than 1/1,000,000 sec

• Some are much longer

Uranium - 238

• Half life = 4.5 billion years

• In 4.5 billion years, half the uranium on earth will be lead!

ISOTOPIC DATING

• Cosmic rays constantly bombard the atmosphere

• Radioactive C14 is ultimately produced.

14C14C14CO214CO2

O2O2

Carbon dioxide takes C14 into the food cycle

Animals eat the plantsso

all animals have some C14 in them

…..soall living things on Earth contain

some C14

After death C12 remains constant

The amount of C14 decreases

Scientists can use this information to determine the age of carbon

containing artifacts

•Carbon-14 Dating

C-14 dating can only be used on something that was previously

alive

Scientists use the elements lead (Pb) and Uranium (U)

to date rocks samples.

Meteor crater, Arizona

Meteor CraterVideo -- Killer Asteroid -- National Geographic