Transcript radioactivity PowerPoint Presentation

ABC’s of Radiation
Howard
AAPT
2005
Matis
- Albuquerque
- [email protected]
1
Howard Matis
Lawrence Berkeley National Laboratory
•
•
•
•
•
•
AAPT 2005 - Albuquerque
Howard Matis - [email protected]
2
What is a Nucleus?
Quarks determine if proton or neutron
• Neutrons
• Protons
• Protons determine chemical propertiesRatio of neutrons to protons
make a nucleus stable or unstable
•
•
•
•
Examples - Isotopes
Uranium-238 (23892U)
–
•
Uranium-235 (23592U)
–
–
•
1 proton, 0 neutrons, mass 1
Deuterium (21D)
–
•
92 protons, 143 neutrons, mass 235
Hydrogen (11H)
–
•
92 protons, 146 neutrons, mass 238
1 proton, 1 neutron, mass 2
Tritium (31T)
–
1 proton, 2 neutrons, mass 3
• Nuclear Stability
• N = # of Neutrons
• Z = # of Protons
• White are the stable nuclei
• For light nuclei, stable nuclei have N=Z
• If too many protons, then a proton will turn into a neutron
• If too many neutrons, a neutron will turn in a proton
•
• How Does it Decay?
• Alpha - lose an alpha particle (a - helium
nucleus)
Beta - emit a beta particle (b - electron or
anti-electron)
Gamma - emit a gamma (g or photon or
light particle)
•
• Alpha Decay
• Alpha particle or helium nucleus emitted
• Nucleus changes mass by four units and charge by two
units
– Alpha particle easily stopped
– 4 x nucleon mass
– +2 Charge
– Big
• Beta Decay
• Beta minus - neutron converts to electron and anti-neutrino
• Beta plus - proton converts to a anti-electron and neutrino
• Nucleus changes charge but not mass number
– Radiation moderately penetrating
– +1 charge
• Small electron
•
• Gamma Decay
• Nucleus changes energy level - emits gamma ray or
photon
• Nucleus stays the same
– Very penetrating
– Very small
– Neutral
• Penetrating Properties of
• Ionizing Radiation
• Cosmic Rays
Another form of Radiation
• Comes from outside the earth
Particles from the sun
• Star dust - from supernova - exploding
stars
Consists of protons and neutrons
•
• Sources of Radiation
• Average radiation exposure in the United
States - 360 mrem Very location
dependent
•
•
•
Additional Sources
Plane travel
•
Living at high elevation - Albuquerque has 2x cosmic radiation
Soil
•
Medical x-rays
•
Occupational exposure
• Is radiation bad for you?
• Too difficult to directly measure risk of low level
• Use high exposure studies to determine radiation
damage
• Extrapolate from high exposure to low
• Model assumes that body does not heal from radiation
exposure
• Similar to calculating the risk of death from a pin prick by
extrapolating from a knife wound
• Relative Risk1 in a million fatality
• 40 tablespoon peanut butter (aflotoxin)
•
2 days in New York City (air quality)
•
•
3 mrem radiation (cancer)
1 mile on motorcycle (collision)
•
300 miles in car (collision)
•
10 charbroiled steaks
•
Smoking 1 cigarette