Chapter #8
Protecting against Internal Radiation

 

Once radionclides  have been taken into the body there is little that can be done in the way of protection. Therefore, one of the the primary objectives of radiation protection  is to prevent the intake of radioactive materials  into the body.

When dealing with external exposure  the methods of protection are fairly straight forward. The nature of the radiation can be determined and the level easily measured. The exposure can be terminated at any time or reduced by the methods previously described. This is not the case for internal radiation for the following reasons:

1. Internal sources  irradiate the body tissues continuously until they have been eliminated from the body by excretion or decay.
2. Long lived radionuclides may remain in the body for years and it is often impossible to increase their rate of elimination.
3. The quantity and distribution of the radionuclide may be difficult to determine making it difficult to assess the dose rate.
4. Alpha  and low energy beta particles   are a very serious internal hazard  . Gamma emitters  are also a hazard but only a fraction of their energy is absorbed before the photons   leave the body. Gamma emitters are more easily located in the body because of the emerging radiation.
5. Some radionuclides are chemically concentrated in organs of the body significantly increasing the local dose.

• Entry of Radionuclides to the Body
  • Elimination of Radionuclides from the Body
• Secondary Dose Limits
  • Annual Limit on Intake
  • Derived Air Concentration
• Committed Dose
  • Tritium
  • Radioiodines
• Particulates
  • Long-lived Particulates
  • The DAC for Particulates
  • Sources of Particulates
• Bioassay
  • Thyroid Counting
  • Urine analysis
  • Whole Body Counting
• Summary
• Assignment