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