Please be Seated The Nucleus Physics is Phun

Please be Seated

The Nucleus Physics is Phun October/November 2008

Topics: Nuclear structure Nuclear reactors Nuclear radiation Useful radiation effects

Nu-cle-ar good Nu-cu-lar not so good

The Electromagnetic Spectrum “Waves” “Photons” c = f λ E = h f c = the speed of light f = frequency λ = wavelength E = photon energy h = Planck’s constant f = frequency

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) Beryllium atom (without neutrons!!)

The Hydrogen Balmer Series

The Nucleus 1. Protons (positive charge) 2. Neutrons (neutral charge) -15 3. Nuclear Diameter ~10 m -10 (atomic diameter ~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” model 2. the “shell” model Models describe aspects of the structure of nuclei and how they behave.

The water-drop model all nucleons “undifferentiated” binding energy is equally distributed

Binding Energy BE = 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 2 E = mc

Average Binding energy per nucleon

Applications of the water-drop model 1. Nuclear fission (very large nuclei break up) 2. Nuclear fusion (very small nuclei fuse together)

Nuclear fission 235 U + n –—> small nuclei + neutrons + ENERGY!! n + 235 U –—> another fission creating a “chain reaction”

Vibrating water drop Click title above to see video

Critical Mass Click title above to see video

Nuclear Chain Reaction Mousetrap Model Click title above to see video

Uncontrolled fission: Atomic bomb (235 U or 239 Pu bomb) Controlled fission: Nuclear reactor

Pressurized Water Reactor From: Joseph Gonyeau, P. E. , Virtual Nuclear Tourist http: //www. nucleartourist. com/

Advantages of Nuclear Power: 1. Clean (no air pollution, including greenhouse gases) 2. Safe compared with other fuels 3. Price competitive with fossil fuels 4. 100 year supply of 235 U 5. Infinite supply (>10, 000 years) of 238 U (if we use breeder reactors)

Patrick Moore*: Going Nuclear A Green Makes the Case (for Nuclear Power) OUTLOOK, Washington Post, April 16, 2006 *Co-founder of Greenpeace (ca. 1970)

In the early 1970 s 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 radiation Not green, Homer!

Nuclear fusion 2 D + 2 D –—> larger nuclei + LOTS OF ENERGY !!

Average Binding energy per nucleon

“Theta Pinch” electromagnetic squeezing to produce fusion

Nuclear Shell Model Discrete energy levels for protons and neutrons and discrete energies for radiation when energy levels change or following radioactive decay

Radiation types: Alpha particle (2 Ps + 2 Ns: 4 He nucleus) Beta particle (- or + electron) Gamma ray (photon energy packet) Neutrons Cosmic Rays

Radiation Exposure

Sources of radiation exposure: 1. Natural Exposure 2. Man-made Exposure

Natural Exposure: 1. Radon gas 2. Cosmic Rays 3. External Environment 4. Internal: The Body

238 U Decay Chain

Cosmic Rays: 1. Cosmic ray muons 2. Other particles

Cosmic Radiation

Man-made radiation: 1. X-rays and γ-rays 2. Nuclear medicine 3. Consumer products (food, etc. )

Sources of Radiation Exposure From: National Institutes of Health

Useful Radiation Effects I Nuclear Power Medical: Diagnostic scans, tracers Magnetic resonance imaging Cancer radiation treatment Plutonium powered pacemaker Medical, dental sterilization

Useful Radiation Effects II Polymer cross-linking Shrink tubing (eg. , turkey wrapping) Ultra-strong materials (eg Kevlar) Tires (replaces vulcanization) Flooring Food irradiation Sterilization of meat Disinfestation of grain and spices Increase shelf life (eg, fruits, veggies)

The “radura. ”

Useful Radiation Effects III Absolute sterilization of food: hospitals and space travel Radioactive dating Insect control Semiconductor doping Testing of space computer technology Environmental 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

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. ~ millions 2. ~ 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

The End See you in January! “ELECTRICITY AND MAGNETISM” We are on the web at http: //www. physics. umd. edu/lecdem/ Animated Gifs compliments of bellsnwhistles. com