RADIATION LAB TIME - DISTANCE - SHIELDING

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RADIATION LABTIME - DISTANCE - SHIELDING

• Health Physics Society -
• Power Reactor Section
• Radiation Science Education

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Time

• Decrease the amount of time you spend near the
  source of radiation, and decrease the amount of
  radiation exposure you receive.
• If you spend a lot of time on the beach,
  ultimately you get a sunburn. By reducing the
  amount of time you spend on the beach, you can
  avoid a sunburn.

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Time Calculation

• ______ counts per minute
• (cpm)
• cpm 2 hours 60 min/hr
• __________ counts
• cpm 10 hours 60 min/hr
• ____________ counts

• Place the lantern mantle in your pocket and take
  a open window measurement.
• If you leave it there for 2 hours, how many
  counts does your leg see?
• If you leave it there for 10 hours, how many
  counts does your leg see?

4
Distance

• The farther away you are from a radiation source,
  the less exposure you will receive.
• Compare this to sitting in front of a fireplace.
  You can sit directly in front or across the room.
• If you are far from the source, your exposure
  will be much lower.

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Distance Calculation

• ______ cpm
• ______ cpm
• ______ cpm

• Measure the radiation level at the surface of the
  plate or mantle.
• Move 2 inches away, repeat the measurement.
• Move 1 foot away, repeat the measurement.
• Calculate the Distance Factor
• DF Contact (cpm) Distance (cpm)

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Shielding

• If you increase the shielding around a radiation
  source, it will decrease your exposure.
• If you stand out in the rain without an umbrella,
  you will get wet.
• But, if you use an umbrella to shield you from
  the rain, you will remain dry and protected.

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Shielding Factor Calculation

• ______ cpm
• ______ cpm
• ______ cpm

• Measure the radiation level on contact with a
  source using the open window detector.
• Place a light piece of material (wood) over the
  object and repeat the measurement.
• Place a heavy piece of material over the object
  and repeat the measurement.
• Calculate Shielding Factor.
• SF Contact (c/m) Shielded (c/m)

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Types of Radiation
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Detector Efficiency By Radiation Type
Voltage Source
Incident Ionizing Radiation



Electrical Current Measuring Device
-
-
-
Anode
Cathode -
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Beta and Gamma Activity Calculation

• Measure the gamma radiation level on contact
  with a source using the closed window detector.
• Assuming the detector sees 1 out of every 100
  gamma rays, calculate the gamma activity.
• Measure the beta gamma radiation level on
  contact with a source using the open window.
• Calculate the beta cpm by subtract the gamma
  cpm from the total beta gamma cpm.
• Assuming the detector sees 1 out of every 10
  beta particles, calculate the beta activity.

• _________ ? (cpm)
• ? activity ? (cpm) ? 0.01 (dpm/cpm)
• __________ dpm
• ___________ ?? (cpm)
• ? (cpm) ?? (cpm) - ? (cpm)
• ? activity ? (cpm) ? 0.1 (dpm/cpm)
• ____________ dpm