Transcript Found in Nature - Bremen High School District 228

Radioactivity Part 2
Nuclear Chemistry
Three types
Alpha Radiation
• Polonium-210 is an alpha emitter. During radioactive decay, it
loses two protons, and becomes a lead-206 atom, which is
stable (i.e., nonradioactive).
Uses
• Radium-226 to treat cancer
• Polonium-210 eliminates static in paper mills by alpha particles
attracting loose electrons
• Americium-241 in smoke detectors to help create electrical
current (smoke will interrupt the current and set off the alarm)
Found in Nature
• Radium-226 & Uranium-238 are present in all rocks, soil, water
• Mining tends to increase exposure in humans & the
environment
Effects
• Lack energy to penetrate skin (must be inhaled, ingested,
absorbed)
• Greatest hazard to lung tissue (inhaled)
• Inside us it’s the most dangerous (Causes cancer)
Human Exposure to Radioactivity
• Radon (Radioactive Gas) is part of the radioactive decay
chain of naturally occurring uranium in soil. You can’t see,
smell or taste radon.
• Health effect = lung cancer
• Test every 2 years
Above 4.0 pCi/L of radan in the
air should be dealt with.
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important for the management/disposal of radioactive materials
During decay – Radon-222 is commonly produced.
•
It’s a gas and seeps up through the soil into the air. It can
accumulate into high concentrations in basements.
•
Gives off alpha particles
•
Its short half life means it emits alpha particles at a high rate.
Beta Radiation
Uses
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Iodine-131 to treat cancer
Strontium-90 is a tracer in medical & agricultural fields
Tritium used for luminous exit signs, dials and watches
Carbon-14 for dating organic matter
Found in Nature
• Carbon-14 & Potassium-40 found in our bodies
Effects
• Lack energy to penetrate solid material
• Direct exposure can redden or burn the skin
• Kills cells
• Iodine-131 accumulates in the thyroid gland
• Strontium-90 accumulates in bone and teeth
Gamma Radiation
Uses
• Cesium-137 cancer treatment, measurements (soil density,
packaging, oil wells)
• Cobalt-60 sterilize medical equipment, treats cancer,
pasteurizes foods and spices, measures thickness of metals
• Technetium-99 used for medical imaging (xrays)
• Can inspect welds and metal parts for leaks and defects
Found in Nature
• Potassium-40 found in soil and water, meats and foods high in
potassium like bananas
Effects
• Can improve durability of wood and plastics
• Radiation sickness
Your annual Radiation Dose
Average annual
radiation dose in US is
360 mrem.
The normal permissible
limit is 5,000 mrem
for those who work
8
Radiation Detection
Approximate amounts of radiation can be detected by the following
devices:
•Film badge
•Geiger-Muller counter
•Scintillation counter
9
Half-life
• Half-life – time required for half of the
original sample of radioactive nuclides
to decay
• Half of the radioactive parent atoms decay
after one half-life. Half of the remainder
decay after another half-life and so
on……..
Half life
The decay of radioisotopes can be used to measure the material’s age.
= radioisotope
At start there
are 16
radioisotopes
After 1 half life
half have
decayed (that’s
8)
= new atom formed
After 2 half
lives another
half have
decayed (12
altogether)
After 3 half
lives another 2
have decayed
(14 altogether)
Decay Curve
shows the decay of radioactive atoms and the remaining radioactive sample.
A very important point here is that we cannot predict when a
particular entity will decay.
 We do know though, that if we had a large sample of a radioactive
substance, some number will decay after a given amount of time.
 Some radioactive substances have a very high “rate of decay”,
while others have a very low decay rate.
Application of Half Life
Radioactive dating
a process used to determine the
approximate age of an object.
Ex. Carbon -14, a radioactive isotope is in all living things.
When organisms die Carbon-14 decreases and can
estimate how long something has been dead.
Video http://www.youtube.com/watch?v=phZeE7Att_s
Application of Half Life
• Iodine-131, a radioactive isotope, is injected into the
body to treat thyroid cancer.
• It’s half life is 8 days – this tells us the rest will
disappear in 80 days
• Good because it will be active long enough for a
cancer treatment, but should be short enough not to
do more damage to healthy cells and organs.
14
Videos
• http://www.youtube.com/watch?v=27qSAqafQ6o
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Alpha, Beta, Gamma http://youtu.be/5oUagoF_viQ
Alpha http://www.youtube.com/watch?v=j5TJRtJxVfs
Beta http://www.youtube.com/watch?v=rW0A5FZTxt0
½ life - http://youtu.be/tzM6aK5QbSU
http://www.youtube.com/watch?v=xhOtKurHa
yo
• Carbon dating