Facebook Instagram Youtube Twitter

Thermoluminescent Dosimeter – TLD vs OSL Dosimeter

TLD – Thermoluminescent Dosimeter

A thermoluminescent dosimeter, abbreviated as TLD,  is a passive radiation dosimeter that measures ionizing radiation exposure by measuring the intensity of visible light emitted from a sensitive crystal in the detector when the crystal is heated. The intensity of light emitted is measured by the TLD reader, depending on the radiation exposure. Thermoluminescent dosimeters were invented in 1954 by Professor Farrington Daniels of the University of Wisconsin-Madison. TLD dosimeters apply to situations where real-time information is not needed. Still, precise accumulated dose monitoring records are desired for comparison to field measurements or for assessing the potential for long-term health effects. In dosimetry, the quartz fiber and film badge types are superseded by TLDs and EPDs (Electronic Personal Dosimeter).

Advantages and Disadvantages of TLDs

Advantages of TLDs

  • TLDs can measure a greater range of doses compared to film badges.
  • Doses from TLDs may be easily obtained.
  • TLDs can be read on site instead of being sent away for development.
  • TLDs are easily reusable.

Disadvantages of TLDs

  • Each dose cannot be read out more than once.
  • The readout process effectively “zeroes” the TLD.

OSL Dosimeter

The OSL dosimetry (Optically Stimulated Luminescence) is a method that has established itself in whole-body dosimetry. As can be deduced, this method is based on optically stimulated luminescence. The OSL dosimeter provides a very high degree of sensitivity by giving an accurate reading as low as 1 mrem for x-ray and gamma ray photons with energies ranging from 5 keV to greater than 40 MeV. OSL dosimeters are designed to provide X, gamma, beta, and neutron radiation monitoring using OSL technology. OSL dosimeters apply to situations where real-time information is not needed. Still, precise accumulated dose monitoring records are desired for comparison to field measurements or for assessing the potential for long-term health effects. In diagnostic imaging, the increased sensitivity of the OSL dosimeter makes it ideal for monitoring employees working in low-radiation environments and pregnant workers. OSL dosimeters offer advantages that can be re-read and high sensitivity (low minimum measurable dose), and they have become popular because of these favorable properties.

OSL materials (e.g., beryllium oxide ceramic) contain defects in their crystal structure that trap electrons released by exposure to radiation. In TLDs, the trapped electrons are subsequently freed by stimulation with heat, while OSL uses stimulation with light. After stimulation by light, the detector releases the stored energy in the form of light, i.e., it is stimulated to emit light. The light output measured with photomultipliers is a measuring unit for the dose. Compared with TLDs, their major difference is that luminescence is produced by a light beam rather than by heat.

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, Instrumentation, and Control. DOE Fundamentals Handbook, Volume 2 of 2. June 1992.

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:

TLD