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									What is radiation?

Radiation is a form of energy. In this situation, we are discussing ionizing radiation that may
cause damage to living tissue and is used in medicine and industry.

Radiation is either electromagnetic waves or particles. A prime examp le of electromagnetic radiation is X-ray and
Gamma radiation. For the particles, Alpha and Beta radiation are the most frequently encountered types. In some
cases, neutrons can also be particle radiation. Because of the nature of the radiation, different techniques are
used to stop the different types of radiations. Lead is good for x -rays and gamma rays, but thick paper stops
alpha particles. Beta radiation is most often stopped using a plastic, like Lucite or Plexiglas. Neutrons are
stopped mostly by using materials with lots of hydrogen, like water or concrete.

Natural background radiation and radioactivity occur naturally in our environment. For example, the radioactive
materials, radium and radon gas occur naturally in our soil, air, and water. All animals and plants contain small
amounts of naturally occurring radioactive materials. We are also exposed to cosmic radiation from the sun,
space, as well as radiation emitted from radioactive material in the bricks and concrete used in building our
homes.

Other sources of radiation exposure are x-ray and nuclear medicine studies, certain consumer products like some
smoke detectors used in our homes to improve our safety. A mrem is a term used to quantify doses and the
potential effect of radiation has on the body.

Typical Radiation Doses
     Source                               Dose                       Source                       Dose

     Natural Radiation                                               Medical
     5-hr jet airplane ride            3 mrem                        Chest X-ray                  8 mrem
     Cosmic radiation                  30 mrem                       CT scan                      1000 mrem
     Internal (own body)               40 mrem/year                  Dental x-ray                 1 mrem

     Consumer Products                                               Occupational
     Building materials                4 mrem/year                   Nuclear Power                450 mrem/year
     Tobacco products                  5,300 mrem/year               Scientist                    25 mrem/year
     (Amount a smoker’s lungs receive from 20 cigarettes per         X-ray Technicians            120 mrem/year
     day)


The average American receives about 1 mrem per day from natural background and medical radiation. Some
areas of the country are more or less than that, based on radon concentrations, soil make up and elevation.

Average U.S. Background and Medical Radiation                               Total: 360 mrem/year
                                Radon 200
                                                                       Medical
                                  mrem
                                                                       55 mrem


                                                                       Cosmic 30
                                            Internal 40     Soil 35      mrem
                                               mrem         mrem



Are there limits for radiation exposure?

A person who works with radiation as part of their job can legally receive 5,000 mrem/year. A facility cannot
expose the general public to more than 100 mrem/year. On a tour of our facility, you will not receive any radiation
exposure above background.

Workers protect themselves from radiation using three main methods: Time, Distance and Shielding.
Whenever possible, we will reduce time we are exposed to a radiation field, increase our distance from source
and use shielding between the source and us. Shielding is dependent on the radiation itself, as shown below.




Glossary

Radiation: Radiation cannot be seen, felt or heard.           Roentgen Equivalent Man (REM): The REM relates
It comes in waveform, like light and in particulate           the RAD to the biological impact caused by different
form (very small particles), like electrons.                  types of radiation. It is a term used to quantify does
                                                              and the potential effect a does of radiation has on the
Radioactive Material: Any material that contains              body. In most cases the rem is that same value as
radioactive atoms. For example, when you get a                the rad. A millirem (mrem) is 1/1,000th of a rem.
nuclear medicine scan, you are injected with
radioactive material.                                         Curie (Ci): The curie is a unit to measure
                                                              radioactivity much as we would measure water in
Radiation Absorbed Dose (RAD): The RAD is a unit              gallons, quarts, or ounces. The amount of
used to measure the amount of energy absorbed in              radioactive material given to a patient is usually in
any material such as concrete, steel, bone, lead,             millicuries (mCi). A mCi is 1/1000th of a curie.
and tissue.
For more information on radiation, see the Radiation Information Network at
               http://www.physics.isu.edu/radinf/index.html
Examples of Applications of Radiation




 Medical:

 Diagnostic X-rays (dental X-rays, CAT scans, mammograms, etc).
 Therapeutic (Co-60, accelerators for cancer treatments).
 Diagnostic nuclear medicine (liver function tests).
 Therapeutic nuclear medicine (1-131 for thyroid cancer treatment).
 Nuclear thermoelectric-powered heart pacemakers.
 Blood irradiation




 Research:

 X-ray diffraction (study of molecular structure - e.g. DNA structure).
 Isotopic tracers (e.g. C-14 to study photosynthesis).
 Isotopic labeling (e.g. P-32 DNA electrophoresis)
 Accelerators (nuclear structure, materials analysis).
 Electron microscopes.


 Consumer Products:

 Cathode ray tubes (TVs)
 Smoke detectors.
 Emergency lighting.
 Static eliminators.
 Luggage screening systems. (X-ray).
Industrial:

                 Sterilization (of medical materials & supplies).
                 Insect eradication (release of insects sterilized by irradiation).
                 Food preservation.
                 Process control (density/Thickness gauges).
                 “Curing” of plastics.
                 Asphalt density
                 Moisture content for soil
                 Industrial radiography (verification of welds & structures).
                 Ion implantation (semiconductor industry).
                 Electron beam applications (e.g. vacuum deposition)




National Defense:

                 Nuclear weapons.
                 Strategic defense (X-ray lasers, particle beams, etc.)


Power:

Nuclear Fission Reactors for electricity (~20% of US electricity).
Nuclear Fission Reactors on Navy ships and submarines.
Nuclear Fusion (future use).
Isotopic electric power sources (satellites, spacecraft).
Visiting labs that use radioactive materials or radioisotopes.

Important things to keep your eye out for:

    1)   How do people protect themselves from the radiation?
    2)   Why are they using the radioisotopes?
    3)   How is the radioisotopes controlled?
    4)   How are the labs that use radioisotopes posted (labeled)?
    5)   How are the radioisotopes labeled?
    6)   What other uses of radiation do you see?

How a Geiger counter (Geiger Mueller detector) works


         GM Instrument
                                               Incident Ionizing Radiation
   Ne +Halogen
                                                 Cathode -
         Gas
                                 +
                             +
                         +
                     +               -
                             -                                   Electrical
                         -
                                                                  Current
                                                                 Measuring
                                                                  Device

                  Anode +                Voltage Source
                                             +    -



The most common type of instrument is a gas filled radiation detector. This instrument works on the principle that
as radiation passes through air or a specific gas, ionization of the molecules in the air occur. Ionization means that
the radiation gives up some energy to the surrounding atoms, causing those atoms to loose their electrons. This
results in ionized atoms (positive charged) and free electrons (negative charge). When a high voltage is placed
between two areas of the gas filled space, the positive ions will be attracted to the negative side of the detector (the
cathode) and the free electrons will travel to the positive side (the anode). In a GM tube as shown above, the
voltage difference is high, so that the ions gain energy as they move towards the anode and cathode, causing more
ionization. The whole tube will ionize, causing a large amount of charge at one time. The charge is collected by the
anode and cathode as a pulse of current in the wires going to the detector. By placing a very sensitive measuring
device along that wire, the pulse measured and displayed as a count. The more radiation which enters the chamber,
the more count are seen by the instrument.

								
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