Transmutation
• Transmutation is the process of atoms of unstable nuclide A changing into atoms of nuclide B.– This can occur naturally (by radioactive
decay) or...– ...as a result of bombardment reactions
• Example: Bombardment of nitrogen-14 with alpha particles... oxygen-17 was formed.
Bombardment Reactions
• The production of synthetic elements (transuranium elements) and non-natural nuclides of other elements are the result of bombardment reactions.
Example:208Bi + 4He --> 210At + ?14N + 4He --> 17O + ?
Chemical Effects of Radiation• Radiations produced from radioactive decay can interact
with atoms and molecules of surrounding material.– Electrons of these atoms/molecules are most directly affected
by radiation.• Excitation• Ionization
• Types of radiation:– Nonionizing - excitation (low energy)– Ionizing (high energy) - resulting in formation of ion pairs
Free Radical Formation
– Free radical: atom, molecule or ion containing an unpaired electron
– Free radicals rapidly react with nearby chemicals.• Stable molecule
• Another free radical
• Example:– H2O + radiation --> H2O+ + e-
– H2O+ + H2O --> H3O+ + OH
(hydroxyl radical)
Radiation Effects on the Human Body
• Protection?: paper or
clothing
metal foil
(such as Al) thick
concrete & Pb
Biochemical Effects of Radiation
• Alpha - due to ingestion– Example: polonium-210 (t1/2 = 138 days)
• Beta - both internal and external
– Example: iodine-131 (t1/2 = 8.0 days)
cobalt - 60 (t1/2 = 5.3 years)
skinburns
• Gamma - this is very effective!!
Alpha, beta, and gamma radiation differ in penetrating ability.
Radiation Detection
• Filters– Example: Film badges used in
nuclear power facilities
• Geiger counters– Contain gas atoms which are
ionized...
Film badges are used to determine a person’s exposure to radiation.
Radiation passing through a Geiger counter ionizes one or more gas atoms, producing ion pairs.
Sources of Radiation• Natural
– Radon seepage, rocks & soils, minerals in the body, cosmic radiation.
• Human-made– Medical X-rays, nuclear medicine,
consumer products, occupational exposure, nuclear fallout (from weapons testing and nuclear power plants)
• Cells that reproduce rapidly are most sensitive to radiation damage.
Nuclear Medicine• Diagnostic uses: use a
radionuclide of an element already present in the body– The movement of the
radionuclide is easily monitored.
Brain scans are obtained using radioactive technetium-99 (emitter), a laboratory-produced radionuclide.
Therapeutic Uses
• used to selectively destroy abnormal cells
Fission & Fusion reactions
• Fission: a large nucleus splits into two medium-sized nuclei with the release of several free neutrons and LOTS of energy.
• Fusion: two small nuclei are collided together to produce a larger nucleus and LOTS of energy.
Fission
• Uranium-235 undergoes fission when a neutron collides with the nuclide.
• If enough radionuclides are present, a “chain reaction” can occur. Watch out!
Fission Nuclear Reactors
• The fission reactor produces heat that is used to turn water into steam in order to drive a turbine.
• The benefits include a large amount of energy from a relatively small amount of fuel.
• The potential risk includes:– Disposal of radioactive products
– Fallout if an explosion occurs
Fusion• Naturally occurs in stars!
Consider what happens during a star’s lifetime!
Ex.1H + 2H --> 1H + 3H -->
Benefits: Nearly unlimited fuel supply; no radioactive wasteRisks: Very difficult to maintain the reaction (need
extremely high Temperatures to keep the reaction going)
The process of nuclear fusion maintains the interior of the sun at the temperature of approximately 15 million degrees.
Comparing Chemical & Nuclear Reactions
