Chapter 4Nuclear Radiation
Background image source: http://www.newprophecy.net/Pak-India_Nuclear_Blast__1.jpg
Natural Radioactivity
• Unstable isotopes• Elements with atomic numbers over 84• Repulsion within the nucleus
• Often written Uranium-238 or U-238• Usually read “Uranium-238”
U238
92
Mass number
Atomic number
Source: http://www.kernchemie.uni-mainz.de/~pfeiffer/home_for_old_atoms.jpg
Radiation• Alpha (α) particle
– He nucleus: 2 protons, 2 neutrons– Heaviest– Charge: 2+– Least penetrating– Most damaging: electron-hungry!
• Destroys DNA and proteins– Sources of exposure: heavy metals in soil
taken up into plants, smoke detectors, cigarettes
Radiation• Beta (β) particle
– High-energy electron from unstable nucleus– Insignificant mass– Charge: 1-– More penetrating than α particles– Not as damaging, also ionizing radiation– Sources of exposure: heavy metals in soil
taken up into plants, cigarettes
Neutron Proton Electron (β particle)
Radiation• Beta (β+) particle
– High-energy positron from unstable nucleus– Insignificant mass– Charge: 1+– More penetrating than α particles– Not as damaging, also ionizing radiation– Sources of exposure: heavy metals in soil
taken up into plants, cigarettes
NeutronProton Positron (β+ particle)
Radiation• Gamma (γ) Ray
– Collection of radiation (energy only)– No mass– No charge– Most penetrating radiation– Least damaging, but most prevalent!– Sources of exposure: medical treatments,
industrial processes, sterilization
Positron (β+ particle)Electron (β particle) γ Ray
Comparison
Half-Life
• The amount of time it takes for one half of a sample to decay
• Ever reaches zero?• Decay curve
Try it!
• Iron-59 has a half-life of 46 days. If the laboratory received a sample of 8.0g Fe-59, how many grams are still active after 184 days?
0.50g
Radiometric Dating• The half-life of an element is used to determine how
long ago something lived• Element studied in a sample depends on what you
need to see!– Fossils: carbon-14 (half-life = 5730 years)– Rocks: potassium-40 (half-life = 1.3 x 109 years)– Medical applications:
• Carbon-11 (half-life = 20 minutes)• Potassium-42 (half-life = 12 hours)• Iron-59 (half-life = 46 days)
Radiometric Dating
Nuclear Fission
• Splitting atoms• “Missing mass” in products—converted to
enormous energy• Starts a chain reaction
– Sufficient quantities of material in close proximity
• Great source of power?
Nuclear Fusion• Joining atoms• More energy required and released than
fission• Need temperatures of at least 100 million °C• “Missing mass” in products—converted to
enormous energy• Great source of power?
Try it!• Complete the following fission reaction:
235U 131Sn + ? + energy
104Mo• Complete the following fusion reaction:
2H + 1H + energy ? + ENERGY
3He
Radiation and You
Source: http://www.uic.com.au/ral.htm
Radiation and You
• Radiation is all around us every day—some harmful and some very useful
• Benefits of radiation
• Dangers of radiation
Radiation and You• Radiation used in war
– WWII was ended after Japan was bombed by U.S. forces
– Hiroshima: uranium fission bomb
– Nagasaki: plutonium fission bomb
– Nearly ¼ million died• Radioactive fallout
– Incorporation into tissues: continuous radiation
Source: http://www.uic.com.au/ral.htm
Nuclear Power• Power Plant Design
Source: http://www.npp.hu/mukodes/tipusok/tipusok-e.htm
Source: http://www.npp.hu/mukodes/tipusok/tipusok-e.htm
Source: http://galileo.phys.virginia.edu/Education/outreach/8thgradesol/RadiationProtection.htm
Nuclear Power• Is it worth the risk?
Source: http://www.uic.com.au/ral.htm
