Dosimeter

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Electronic Personal Dosimeter (EPD). These give a dose rate and accumulated dose reading via the display.

Dosimeters measure an individual's or an object's[1] exposure to radiated energy. This article concentrates on the radiation dosimeter, which measures exposure to ionizing radiation.

The radiation dosimeter is of fundamental importance in the disciplines of radiation dosimetry and health physics. The ICRP states that if a personal dosimeter is worn on a position on the body representative of its exposure, assuming whole-body exposure, the value of ambient dose equivalent H(10) is sufficient to provide an effective dose value suitable for radiological protection. [2]

Other types of dosimeters are sound dosimeters, ultraviolet dosimeters and electromagnetic field dosimeters.

Applications[edit]

Ionizing radiation, such as X-rays, alpha rays, beta rays, and gamma rays, are undetectable by the human senses, therefore a measuring device is used to detect, measure and record these, and in some cases give an alarm when a preset level is exceeded.

Ionising radiation damage to the human body is cumulative, and is related to the total dose received, for which the SI unit is the sievert. Therefore, workers exposed to radiation, such as radiographers, nuclear power plant workers, doctors using radiotherapy, those in laboratories using radionuclides, and some HAZMAT teams are required to wear dosimeters so their employers can keep a record of their exposure to verify that it is below legally prescribed limits. Such devices are known as "legal dosimeters", meaning that they have been approved for use in recording personnel dose for regulatory purposes.

Crew members aboard NASA Space Shuttle missions had access to four types of active dosimeters should a radiation contingency occur. Crew members were required to wear passive dosimeters at all times throughout the mission.[3]

Types[edit]

Common types of wearable dosimeters for ionizing radiation include:

Quartz fiber dosimeters have to be prepared, usually daily, with a high voltage positive charge. As the gas in the dosimeter chamber becomes ionized by nuclear radiation the charge leaks away, causing the fiber indicator to rise up the graduated scale.[4]

Film badge dosimeters are for one-time use only. The level of radiation absorption is indicated by a change to the film emulsion, which is shown when the film is developed.

Both the quartz and film badge types are being superseded by the TLD and Electronic Personal Dosimeter. The latter has a number of sophisticated functions such as alarming at preset levels and live readout of dose accumulated.

Industrial process use[edit]

Manufacturing processes that treat products with ionizing radiation, such as food irradiation, use dosimeters to calibrate doses. These are different from personal dosimeters because they usually must have a greater range. They often consist of small blocks of material such as perspex (acrylic).

The dosimetry of neutron radiation uses specialised devices, such as superheated drop detectors.

Gallery[edit]

See also[edit]

References[edit]

  1. ^ For example: Mejdahl, V.; A. G. Wintle (1984). "Thermoluminescence applied to age determination in archaeology and geology". Thermoluminescence and thermoluminescent dosimetry. Boca Raton: CRC Press. pp. 133–190. Retrieved 2009-09-14. "Abstract: Thermoluminescent (TL) dating is used on non-pottery materials, including burnt flints and stones, calcareous deposits, volcanic lavas, and geological sediments. The development of new TL dosimeters and new detectors for radioactivity measurements has increased the ability to measure accurately the dose rate experienced by the samples today." 
  2. ^ ICRP pub 103 para 138
  3. ^ "Radiation Equipment". Retrieved 10 March 2011. 
  4. ^ Frame, Paul (2007-07-25). "Pocket Chambers and Pocket Dosimeters". Health physics historical instrument museum collection. Oak Ridge Associated Universities. Retrieved 2008-11-08. 

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