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University of Colorado Denver

Environmental Health and Safety, University of Colorado Denver

Radiation Safety

Dosimetry Program

Dosimetry devices are used to monitor an individual for exposure to penetrating sources of radiation. Explore the tabs below for further details on the dosimetry program. If you have questions, please email and list "TLD" in the subject line, or contact 303-724-0345 and press option 2 to speak to the receptionist.

Please visit our Forms​ page and download the "Dosimetry Badge Request" form to request a dosimetry badge.

​The Colorado Department of Health and Environment (CDPHE) requires radioactive material licensees to monitor adults "... likely to receive, in one year from sources external to the body, a dose in excess of 10 percent of the applicable limits in 6 CCR 1007-1 Part 4.6.1 ..."

This means any adult likely to receive a whole body dose of 500 mrem, in one year, must be monitored for penetrating exposure. Exposure to penetrating sources of radioactive material at CU Anschutz is not common and review of personal monitoring results confirms that an individual is unlikely to receive a dose in excess of 500 mrem in one year. In fact, monitoring results show occupational exposure to penetrating radiation has not exceeded 100 mrem in one year.

The As Low As Reasonably Achievable (ALARA) program provides two dose levels (ALARA I and ALARA II) whereby the Radiation Safety Officer (RSO) investigates potential exposures exceeding the outlined levels.

The RSO continuously reviews radioactive material use and personal monitoring results to ensure compliance with the regulatory requirements and the ALARA program.

​A thermoluminescence dosimeter (TLD) provides several advantages over film badges. A TLD may be worn for longer periods without affecting the accuracy of the dose measurement. They can report a dose as low as 1 mrem compared to the 10 mrem minimal detectable of a film badge. A TLD may also be reused after it is read compared to the one-time use of the film badge.

It is important to note that doses received below the detectable limit of the monitoring device are generally reported as "not detectable" (ND). Due to the low minimal detectable dose of the TLD, monitored individuals may see exposure numbers on their reports compared to the "ND" designation on reports from film badge readings. If you have any questions regarding exposure report results you receive, please contact the RSO.

Any individual who has the potential to exceed 10% of the applicable regulatory limit are monitored. At CU Anschutz, this includes individuals handling most gamma or x-ray emitters and those handling greater than 1 mCi amounts of P-32. Extremity dosimetry will be determined by the RSO, but generally will be required for handling 5 mCi or more of gamma or x-ray emitters, and 1 mCi or more of high energy beta emitters like P-32.

The Committee on Ionizing Radiation or the RSO may require monitoring for individuals that fall outside of the parameters outlined above if deemed necessary.

​The TLD exchange frequency is either on a monthly or a quarterly basis. The designated dosimetry badge contact for the lab is responsible to ensure all monitored individuals at the lab return their badges in a timely manner. Exchanges are typically handled via campus mail. New badges should arrive at the beginning of the monitoring period. Return badges to EHS, mail stop F-484, in the envelope the new badges arrived in. A missing badge report will be sent to the badge contact for any badges not returned.

TLDs must be returned by the 15th of the month following the monitoring period. For example, the 1st Quarter TLD badges need to be returned no later than April 15.

Quarters are divided into the following:

  • 1st Quarter:  January 1 - March 31
  • 2nd Quarter:  April 1 - June 30
  • 3rd Quarter:  July 1 - September 30
  • 4th Quarter:  October 1 - December 31
​Because of the potential for damage to a developing fetus, dose limits for declared pregnant workers are lower than the dose limits for other adults. Workers who declare pregnancy are monitored according to lower dose limits.

For purposes of radiation safety regulations, a radiation worker is considered pregnant only after she has declared her pregnancy to her employer in writing, along with the estimated date of conception.

Workers are encouraged to declare a pregnancy as soon as it becomes known to them, and to inform the Radiation Safety Officer in writing.

To declare pregnancy to the RSO, visit our Forms​ page and download the "Declaration of Pregnancy" form.

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