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Nuclear Energy
Chapter 15
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RADIOACTIVITY15.1
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Remember:
Atoms are made of protons, neutrons, and electrons
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Most atoms are stable
They have a correct
balance of protons and
neutrons.
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Other atoms are unstable
They have an “off-balance”
number of protons and
neutrons.
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radioactive
Atoms whose nuclei are unstable are said to be
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Eventually, these atoms breakdown.
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The process is called “radioactivity”.
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Radioactivity is not new.
Radioactivity is not caused by man.
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Radioactive decay in Earth’s
interior heats the water for
geysers
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Radioactive decay in Earth’s interior heats the water for hot springs
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Most of the radiation we
encounter
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Nuclear Technology - Pros
• Medical X-rays & Anti Cancer Treatments
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Nuclear Technology - Pros
• Smoke detectors
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Nuclear Technology - Pros
• Nuclear Energy
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Nuclear Technology - Cons
• Nuclear Disaster
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Nuclear Technology - Cons
• Nuclear Weapons
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Nuclear Technology - Cons
• Nuclear Weapons
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Nuclear Technology Demands Responsibility
• Safeguard nuclear material• Safe, clean disposal• Protect the environment for
future generations
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It’s up to you to make the
decisions for the future!
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Alpha, Beta, and Gamma Rays
Chapter 15.2
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Radioactive elements emit 3 different types of particles
alphabeta
gamma
αβ
γ
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α particles are positively charged
β particles are negatively charged
γ particles are neutral
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• http://www.youtube.com/watch?v=o-9yt7OAYmE
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α particles are He nuclei
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α particles are Helium nuclei
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α particles• Relatively low speed• Eventually become
HE• Easy to shield against• Can’t go through
paper or clothing
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β particles are electrons
• Neutrons “decay”• Produce a proton and
electron
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β particles
• Faster than α particles• Can penetrate paper and clothes• Can penetrate and damage skin• Can not penetrate denser material like aluminum
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γ (gamma) rays are pure energy
• Gamma rays have more energy than visible light, UV light or X-rays
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γ (gamma) rays• Can easily
penetrate and damage living tissue
• Can penetrate most materials – except lead
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Let’s Compare
PenetratingPower
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γ (gamma) rays can help preserve food
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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.
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Question
• You can throw one away.
• Of the other two, you must hold one in your hand and place one in your shirt pocket.
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Question
• What can you do to minimize your exposure?
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Answer
• Hold the alpha emitter in your hand.
• The skin on your hand will shield you.
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Answer
• Put the beta emitter in your pocket.
• The combined thickness of you skin and clothing should shield you from the beta emissions.
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Answer
• THROW AWAY THE GAMMA EMITTER!
• Because it would penetrate your body from any of these locations.
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Answer
• In a perfect world……
• Distance yourself from all the rocks!.
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Environmental Radiation
Chapter 15.3
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Most radiation we encounter originates in nature
• Common rocks and minerals
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Which family is exposed to more radiation?
The one living in a Brick house?
Or the one living in a wooden house?
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• More radiation exposure
• Naturally Occurring
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RadonA Common Source
of Radiation
• Radon
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• Heavy, inert gas• Arises from uranium deposits
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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.
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How radon produces cancer
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Levels vary with geology
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You can check radon levels with a
test kit
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High levels require action
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Here’s another interesting question….
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Which is a greater source of radiation?
Coal Combustion Nuclear power
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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.
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• 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
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RADIATION DAMAGE TO THE BODY
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Remember
• Most of the radiation we receive is from natural sources and medical procedures
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The human body itself is a source of radiation!
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The radiation comes from the potassium we eat.
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Our bodies contain about 200 mg K
≈ 180 mgother Kisotopes
≈ 20 mg K40
*radioactive*
β emitter
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Between every heartbeat…
≈ 5000 K40 undergo spontaneousradioactive decay!
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Radiation is everywhere!
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Radiation can cause damage to cells
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Radiation can cause serious burns and hair loss
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Cells can repair radiation damage if it is not too severe
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Radiation can damage DNA
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Radiation can damage DNA resulting in cancer
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High doses of radiation can damage DNA resulting hereditary
birth defects
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Common sense
• Avoid radiation when possible
• All radiation can not be avoided
• Most is simply part of nature
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HALF- LIFEChapter 15.5
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Radioactive isotopes decay at different rates
• Measured in terms of a characteristic time
• “Half-life”
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Half-life
The time needed for half the radioactive atoms of a radioactive
material to decay
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Radium (Ra 226)
• Half life = 1620 years
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Half lives are constant
• Not affected by external conditions• Some are less than 1/1,000,000 sec
• Some are much longer
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Uranium - 238
• Half life = 4.5 billion years
• In 4.5 billion years, half the uranium on earth will be lead!
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ISOTOPIC DATING
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• Cosmic rays constantly bombard the atmosphere
• Radioactive C14 is ultimately produced.
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14C14C14CO214CO2
O2O2
Carbon dioxide takes C14 into the food cycle
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Animals eat the plantsso
all animals have some C14 in them
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…..soall living things on Earth contain
some C14
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After death C12 remains constant
The amount of C14 decreases
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Scientists can use this information to determine the age of carbon
containing artifacts
•Carbon-14 Dating
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C-14 dating can only be used on something that was previously
alive
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Scientists use the elements lead (Pb) and Uranium (U)
to date rocks samples.
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Meteor crater, Arizona
Meteor CraterVideo -- Killer Asteroid -- National Geographic