Radiation Protection Principles – Time – Distance – Shielding

ionizing radiation - hazard symbol
ionizing radiation – hazard symbol

Radiation protection is the science and practice of protecting people and the environment from the harmful effects of ionizing radiation. The International Atomic Energy Agency (IAEA) defines radiation protection as:

“The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this”

It is a serious topic not only in nuclear power plants, but also in industry or in medical centres. According to the IAEA, radiation protection can be divided into three groups:

  • occupational radiation protection, which is the protection of workers in situations where their exposure is directly related to or required by their work
  • medical radiation protection, which is the protection of patients exposed to radiation as part of their diagnosis or treatment
  • public radiation protection, which is the protection of individual members of the public and of the population in general

According to the ICRP (Publication 103), the System of Radiological Protection is based on the following three principles:

  1. Justification. “Any decision that alters the radiation exposure situation should do more good than harm.”
  2. Optimisation of Protection. “Doses should all be kept as low as reasonably achievable, taking into account economic and societal factors.” (known as ALARA or ALARP)
  3. Dose Limitation. “The total dose to any individual … should not exceed the appropriate limits.”

See also: ICRP, 2007. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37 (2-4).

Radiation Protection Principles – Time – Distance – Shielding

External exposure is radiation that comes from outside our body and interacts with us. In this case, we analyze predominantly exposure from gamma rays, since alpha and beta particles, in general, constitute no external exposure hazard because the particles generally do not pass through skin. The source of radiation can be, for example, a piece of equipment that produces the radiation like a container with a radioactive materials, or like an x-ray machine. In radiation protection there are three ways how to protect people from identified external radiation sources:

  • radiation protection pronciples - time, distance, shielding
    Principles of Radiation Protection – Time, Distance, Shielding

    Limiting Time. The amount of radiation exposure depends directly (linearly) on the time people spend near the source of radiation. The dose can be reduced by limiting exposure time.

  • Distance. The amount of radiation exposure depends on the distance from the source of radiation. Similarly to a heat from a fire, if you are too close, the intensity of heat radiation is high and you can get burned. If you are at the right distance, you can withstand there without any problems and moreover it is comfortable. If you are too far from heat source, the insufficiency of heat can also hurt you. This analogy, in a certain sense, can be applied to radiation also from radiation sources.
  • Shielding. Finally, if the source is too intensive and time or distance do not provide sufficient radiation protection, the shielding must be used. Radiation shielding usually consist of barriers of lead, concrete or water. There are many many materials, which can be used for radiation shielding, but there are many many situations in radiation protection. It highly depends on the type of radiation to be shielded, its energy and many other parametres. For example, even depleted uranium can be used as a good protection from gamma radiation, but on the other hand uranium is absolutely inappropriate shielding of neutron radiation.
References:

Radiation Protection:

  1. Knoll, Glenn F., Radiation Detection and Measurement 4th Edition, Wiley, 8/2010. ISBN-13: 978-0470131480.
  2. Stabin, Michael G., Radiation Protection and Dosimetry: An Introduction to Health Physics, Springer, 10/2010. ISBN-13: 978-1441923912.
  3. Martin, James E., Physics for Radiation Protection 3rd Edition, Wiley-VCH, 4/2013. ISBN-13: 978-3527411764.
  4. U.S.NRC, NUCLEAR REACTOR CONCEPTS
  5. U.S. Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.

Nuclear and Reactor Physics:

  1. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).
  2. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.
  3. W. M. Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1.
  4. Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317
  5. W.S.C. Williams. Nuclear and Particle Physics. Clarendon Press; 1 edition, 1991, ISBN: 978-0198520467
  6. G.R.Keepin. Physics of Nuclear Kinetics. Addison-Wesley Pub. Co; 1st edition, 1965
  7. Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.
  8. U.S. Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.
  9. Paul Reuss, Neutron Physics. EDP Sciences, 2008. ISBN: 978-2759800414.

See above:

Radiation Protection