Post on 14-Jan-2016
Pleasebe
Seated
The Nucleus
Physics is Phun
October/November 2008
Topics:Nuclear structureNuclear reactorsNuclear radiationUseful radiation effects
Nu-cle-ar good
Nu-cu-lar not so good
The Electromagnetic Spectrum
c = f λ
c = the speed of lightf = frequency
λ = wavelength
E = h fE = photon energy
h = Planck’s constantf = frequency
“Waves” “Photons”
Infrared
Visible light
Ultraviolet
“Members” of the
Electromagnetic Spectrum
Atomic models:1. the “plum-pudding” model
2. the “nuclear” model(tiny nucleus with electrons
in much larger orbits)
Berylliumatom(withoutneutrons!!)
The HydrogenBalmer Series
The Nucleus1. Protons (positive charge)2. Neutrons (neutral charge)3. Nuclear Diameter ~10-15 m
(atomic diameter ~10-10 m)The term “nucleon” refers to either a proton or a neutron in the nucleus.
The term “nuclide” refers to a nucleus with a specific number of protons and neutrons.
The Chart of Nuclides
Stable Nuclides All Known Nuclides
Nuclear models:
1. the “water-drop” model2. the “shell” model
Models describe aspects of the structure of nucleiand how they behave.
The water-drop model
all nucleons “undifferentiated”
binding energy is equally distributed
Binding EnergyBE = M(Z protons) + M(N neutrons) – M(Nucleus)
Atomic Number: A = Z + N
BE is the energy required to separate the full nucleus into its
individual protons and neutrons
E = mc2
Average Binding energy per nucleon
Applications of thewater-drop model
1. Nuclear fission (very large nuclei break up)
2. Nuclear fusion(very small nuclei fuse together)
Nuclear fission235U + n –—> small nuclei + neutrons + ENERGY!! n + 235U –—> another fissioncreating a “chain reaction”
Vibrating water drop
Click title above to see video
Critical Mass
Click title above to see video
NuclearChain ReactionMousetrap Model
Click title above to see video
Uncontrolled fission:Atomic bomb
(235U or 239Pu bomb)
Controlled fission:Nuclear reactor
Pressurized Water Reactor
From: Joseph Gonyeau, P.E., Virtual Nuclear Touristhttp://www.nucleartourist.com/
Advantages of Nuclear Power:
1. Clean (no air pollution, including greenhouse gases)2. Safe compared with other fuels3. Price competitive with fossil fuels4. 100 year supply of 235U5. Infinite supply (>10,000 years) of
238U (if we use breeder reactors)
Patrick Moore*: Going NuclearA Green Makes the Case(for Nuclear Power)OUTLOOK, Washington Post, April 16, 2006
*Co-founder of Greenpeace (ca. 1970)
In the early 1970s when I helped found Greenpeace, I believed that nuclear energy was synonymous with nuclear holocaust, as did most of my compatriots. ….
…. Thirty years on, my views have changed, and the rest of the environmental movement needs to update its views, too, because nuclear energy may just be the energy source that can save our planet from another possible disaster: climate change.
"It doesn’t matter what is true; what matters is what people think is true."
Founder, Greenpeace (2000)
UM Reactor Core
Blue Cerenkov radiation
UM Reactor Core
Blue Cerenkov radiationNot green, Homer!
Nuclear fusion
2D + 2D –—> larger nuclei
+ LOTS OF ENERGY!!
Average Binding energy per nucleon
“Theta Pinch”electromagnetic squeezing
to produce fusion
Nuclear Shell ModelDiscrete energy levels
for protons and neutronsand
discrete energies for radiationwhen energy levels change
or following radioactive decay
Radiation types:Alpha particle (2 Ps + 2 Ns: 4He nucleus)
Beta particle (- or + electron)Gamma ray (photon energy packet)
Neutrons
Cosmic Rays
Radiation Exposure
Sources of radiation exposure:1. Natural Exposure2. Man-made Exposure
Natural Exposure:1. Radon gas2. Cosmic Rays3. External Environment4. Internal: The Body
238U Decay Chain
Cosmic Rays:1. Cosmic ray muons2. Other particles
Cosmic Radiation
Man-made radiation:1. X-rays and γ-rays2. Nuclear medicine3. Consumer products (food, etc.)
From: National Institutes of Health
Sources of Radiation Exposure
Useful Radiation Effects INuclear Power
Medical:Diagnostic scans, tracersMagnetic resonance imagingCancer radiation treatmentPlutonium powered pacemakerMedical, dental sterilization
Useful Radiation Effects IIPolymer cross-linking
Shrink tubing (eg., turkey wrapping)Ultra-strong materials (eg Kevlar)
Tires (replaces vulcanization)Flooring
Food irradiationSterilization of meatDisinfestation of grain and spicesIncrease shelf life (eg, fruits, veggies)
The “radura.”
Useful Radiation Effects IIIAbsolute sterilization of food:
hospitals and space travelRadioactive datingInsect controlSemiconductor dopingTesting of space computer technologyEnvironmental studies:
air purity, global warming, ozone
The Nuclear Waste
Test
Test Question #1 Suppose that all of the electrical energy for the world for the next
500 years were obtained from nuclear reactors. Further suppose that all of the nuclear waste from these reactors were dissolved and spread uniformly throughout the
oceans of the world.
Which statement is true:
1. The oceans would be a vast wasteland, unable to support life.
2. Much death and damage to ocean life would be caused.
3. Any effect would be so small that it would be virtually impossible to see
Which statement is true:
1. The oceans would be a vast wasteland, unable to support life.
2. Much death and damage to ocean life would be caused.
3. Any effect would be so small that it would be virtually impossible to see
Test Question #2
Consider all of the people throughout history who have been
exposed to man-made nuclear radiation, such as Hiroshima and Nagasaki, Chernobyl, Three Mile
Island, nuclear bomb tests, accidental spills, etc.
Which number most nearly approximates how many children conceived and born later to these
people suffered genetic damage due to a parent’s exposure, excluding
exposure during pregnancy?
1. ~ millions2. ~ thousands
3. zero
Which number most nearly approximates how many children conceived and born later to these
people suffered genetic damage due to a parent’s exposure, excluding
exposure during pregnancy?
1. ~ millions2. ~ thousands
3. zero
Reference materials:
Nuclear Physics and Society web site
Joseph Gonyeau's Virtual Nuclear Tourist! Nuclear Plants Around the World
Albert B. Reynolds: Bluebells and Nuclear Energy; Cogito Books, Madison, Wisconsin (1996)
A Nuclear Sunset
We are on the web at
http://www.physics.umd.edu/lecdem/
Animated Gifs compliments of bellsnwhistles.com
The EndSee you in January!
“ELECTRICITY AND MAGNETISM”