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University of Colorado Denver

Environmental Health and Safety, University of Colorado Denver

Radiation Safety

Dosimetry Program

​Dosimetry Monitoring Program Changes - Effective July 1, 2014

Film badges have been the university's primary device to monitor personal exposure to ensure compliance with regulatory limits. Film technology is being phased out by the supplier and thermoluminescent dosimeters (TLDs) will become the preferred monitoring device effective July 1, 2014.

The tabs below provide additional information about the changes. If you still have questions, please email and place TLD in the subject line, or contact 303-724-0345 and press option 2 to speak to the receptionist.

​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 dose of 500 mrem, in one year, must be monitored for penetrating exposure. Exposure to penetrating sources of radioactive material in a biomedical research setting 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) must investigate potential exposures that exceed the outlined levels. Any individual who exceeds either an ALARA I or ALARA II level will be contacted by the RSO to investigate the reading.

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

​TLDs provide several advantages over film badges. The 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 the 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). The minimal detectable dose for film badges is 10 mrem. This means any exposure received below 10 mrem (i.e. 1 - 9 mrem) is reported as "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.

The biggest change in the monitoring requirements affects those individuals handling P-32. As a high energy beta emitter, P-32 can produce bremmstrahlung x-rays, which are considered a penetrating radiation. Calculations were performed to evaluate whether an individual handling 1 mCi of P-32 would receive a dose in excess of 500 mrem. Furthermore, review of exposure records confirms individuals handling 1 mCi or less of P-32 have not exceeded 500 mrem. A determination was made that individuals handling 1 mCi or less of P-32 would not exceed a whole body dose in excess of 500 mrem. Therefore, monitoring any individual handling 1 mCi of P-32 will not be required.

Individuals who handle greater than 1 mCi amounts of P-32 would be required to be monitored for whole body exposure. Additionally, these individuals will continue to receive an extremity dosimeter (i.e. finger ring).

Individuals handling most gamma or x-ray emitters will also be monitored for whole body exposure. Extremity dosimetry will be evaluated by the RSO, but generally will be required for handling 5 mCi or more of gamma or x-ray emitters.

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 for most monitored individuals will be on a quarterly basis. For each quarter, the Radiation Safety staff will meet with each lab to exchange TLDs.  TLDs must be exchanged 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 through March 31
  • 2nd Quarter:  April 1 through June 30
  • 3rd Quarter:  July 1 through September 30
  • 4th Quarter:  October 1 through December 31

Rad Safety will arrange an exchange with the lab's designated dosimetry badge contact after the new monitoring period badges have arrived and prior to the 15th of the month following the monitoring period. The badge contact will be responsible to ensure all monitored individuals return their TLD for exchange with Rad Safety.

Monitored individuals who fall into an exchange frequency other than quarterly will be notified and instructed on the exchange protocol.

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