why do you need to know about nuclear physics? 1.radioactivity and health radon pet scans...
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Why do YOU need to know about Nuclear Physics?
1. Radioactivity and health
• Radon
• PET scans
• occupational hazards
2. Determining isotope ratios
• Dating human artifacts, rocks, meteorites
• Detecting illicit nuclear weapons programs
3. Nuclear weapons (fission, fusion)
4. Nuclear power plants
5. Nuclear cleanup
• health issues
• costs!
6. Future power source - controlled nuclear fusion
These issues affect your health, your power bills, and how and where and why wars are fought.
Bohr pictured the electron as orbiting the nucleus in certain quasi-stable orbits. Light is emitted when
the electron jumps from one orbit to another.
PHOTON:
E = hf,
(h= Planck’s constant)
The periodic table can be formed by listing the elements in order of increasing atomic weight and
then cutting the list at certain points. Elements with similar chemical properties are then aligned in columns.
The basic building blocks of the nucleus are the proton and the neutron.
How big are these particles?
Alpha decay of radium-226. The daughter isotope is radon-222.
Beta decay of lead-214. The daughter isotope, bismuth-214, has a higher atomic number than lead.
Gamma decay of bismuth-214. The daughter isotope is a more stable (lower-energy)
version of the original bismuth-214.
Decay curve for radon-222. The amount remaining decreases by one-half every 3.8 days, the half-life.
NUCLEAR REACTION
The collision of an alpha particle and a nitrogen nucleus results in a proton being emitted and an oxygen-17 nucleus remaining in place of nitrogen.
Lecture Quiz #39 - Question 1:
An allowed reaction is n = p+ + e- +
Consider the possible reaction n = p+ + 2e- + This would not be allowed mostly because of conservation of:
A. energy
B. linear momentum
C. angular momentum
D. electric charge
E. mass
Lecture Quiz #39 - Question 2:
An allowed reaction is n = p+ + e- +
Consider the possible reaction n = 2p+ + 2e- + This would not be allowed mostly because of conservation of:
A. energy
B. linear momentum
C. angular momentum
D. electric charge
E. mass
Nuclear Processes:
1. Alpha decay
2. Beta decay
3. Gamma decay
4. Fission
5. Fusion
Alpha decay of radium-226. The daughter isotope is radon-222.
Beta decay of lead-214. The daughter isotope, bismuth-214, has a higher atomic number than lead.
Gamma decay of bismuth-214. The daughter isotope is a more stable (lower-energy)
version of the original bismuth-214.
Reading Quiz
Which of these nuclei has more than one proton?
1. helium
2. hydrogen
3. deuterium
4. tritium
The proton and neutron numbers for the most common isotopes of several elements. The nucleus gets larger
as the number of protons and neutrons increases.
Nuclear Processes:
1. Alpha decay
2. Beta decay
3. Gamma decay
4. Fission
5. Fusion
Lecture Quiz #40 - Question 1:
Consider the possible reaction
What are the mass number and atomic number of X?
€
2He4 +7N
14⇒ ?X? +1H
1
€
1. 12X16
2. 8X17
3. 9X18
4. 7X18
5. 5X17
Lecture Quiz #40 - Question3:
In a nuclear power plant, the uranium fuel produces power from the process called
A. Fusion
B. Fission
C. Chemical Bonding
D. Photosynthesis
E. Mass Number
FISSIONBarium-142 and krypton-91 are two possible fission fragments produced when a neutron is absorbed by
uranium-235, causing a fission reaction.
Nuclear energy comes from E = mc2.Nuclear Fusion
Nuclear reaction: He4 + Be9 -> C12 + n1
Initial mass = 13.014 uFinal mass = 13.008 u m = 0.006 u ~ 10 me
1u=1.7x10-27 kg
So mcx 10-13 Joules ~ 6,000,000 eV
~ 6 million chemical bonds!!!
Similar results obtained from FISSION:
n + U235 -> Kr91 + Ba142 + 3n
Lecture Quiz 40: Question 4
Initially a container holds only the element Iron (Fe). Later it is found to still have only Iron, but these nuclei now have less energy.
This could be explained by:
A. Alpha decay
B. Beta decay
C. Gamma decay
D. Fission
E. Fusion
F. More than one of the above
G. None of the above.
Lecture Quiz 40: Question 5
Initially a container holds only the element Radium (Ra). Later it is found to also contain some Actinium (Ac).
This could be explained by:
A. Alpha decay
B. Beta decay
C. Gamma decay
D. Fission
E. Fusion
F. More than one of the above
G. None of the above.
Lecture Quiz 40: Question 6
Initially a container holds only the element Plutonium (Pu). Later it is found to also contain some Tin (Sn).
This could be explained by:
A. Alpha decay
B. Beta decay
C. Gamma decay
D. Fission
E. Fusion
F. More than one of the above
G. None of the above.
A chain reaction involving nuclear fission. Neutrons are produced in each fission of a uranium-235 nucleus,
which, in turn, can initiate more fission reactions.
ISOTOPIC ENRICHMENT
Natural Uranium: 0.7% U235 (0.7 billion years)
99.3% mostly U238 (4.5 billion years)
Only U235 is fissile, releasing neutrons spontaneously.
These neutrons are too fast to cause a chain reaction at this concentration.
If they are slowed down, chain reaction is adequate for a nuclear power plant.
If the U235 is enriched to maybe 7%, then the fast neutrons can cause a chain reaction. If there is a critical mass, a nuclear bomb is possible.
Chernobyl type ReactorGraphite was used to moderate to slow down the neutrons.Control rods set the number of neutrons.This is a “mechanically” controlled system.
U.S. Reactors
The Reactors are based on water moderator. The reactor get hot the water turns to steam and the reactor stops. If the reactor cools the water becomes more dense and the reactor warms up.
This is a “naturally” stable system.
A diagram of a modern pressurized-water nuclear reactor. Hot water coming from the reactor is
converted to steam when the pressure is reduced in the steam generators. The steam turns the turbines, which power the electric generator.
€
1H2+1H
3⇒ 2He4
1+0n1
FUSIONA deuterium nucleus and a tritium nucleus combine to form a helium-4 nucleus and a neutron. The difference in the masses is converted to the kinetic energy of the emerging particles.
FUSION
mass difference ~ 0.019 u ~ 30 me
energy gain ~ 20,000,000 chemical bonds!!!