Dosimetry and Bioassay Requirements

DOSIMETRY

Radiation dosimetry is required for all personnel likely to receive a dose greater than 10 percent of the occupational dose limits set by the Nuclear Regulatory Commission or those who may enter a high radiation area. Evaluations of historical dosimetry data are performed by the RSS, as needed, to determine if personnel groups are likely to receive 10 percent of the occupational dose limits. Some groups will receive dosimeters even if they are not likely to receive 10 percent of the NRC limits. The RSS has developed a set of criteria used to evaluate the need for personnel dosimetry. Personnel assigned radiation dosimeters shall wear them when working with radiation sources. If a Radiation Worker (RW) is assigned dosimetry and plans to receive a diagnostic or therapeutic treatment with RAM (radiopharmaceuticals), then the RW must notify the RSS prior to the treatment so the RSS can advise the RW on the particulars associated with how to continue to monitor occupational exposure without it being affected by the radiation from the treatment or scan.

If a RW declares a pregnancy, then the pregnant worker will be issued a fetal dosimeter to monitor the external exposure levels to the fetus. Declaration of pregnancy is voluntary. The need for monitoring internal dose to the fetus will be assessed based on the likelihood of an intake of RAM by the pregnant worker. The results of the monitoring will be reviewed by the RSS monthly throughout the remainder of the pregnancy. Consult the assigned Health Physicist (HP) with any questions regarding dosimetry.

The following are criteria used by the RSS to determine the need for dosimetry.

  • RAM use
    • Dosimeters are not needed when using:
      • Only low-energy beta emitters (<300 keV max). Examples include H-3 and C-14.
      • Source material in basic physical and chemical manipulations, includes U(nat), U(depl), and Th(nat).
      • Gamma or high-energy beta emitters (>300 keV max) with activity <1 mCi.
    • An evaluation for needing dosimeters should be performed when using:
      • Source material in a complex process.
      • Gamma emitters with energy >100 keV. Examples include Tc-99m, F-18, Cu-64, I-124.
      • Gamma or high-energy beta emitters (>300 keV max) with activity ≥ 1 mCi.
      • Any radionuclide with activity greater than or near 1 Ci.
      • Alpha emitters.
    • Dosimeters are required when:
      • Using radiopharmaceuticals in a clinical setting.
      • Participating in HDR procedures.
  • X-ray use
    • Dosimeters are not needed when:
      • X-rays are only used when personnel are in a control room.
    • An evaluation for needing dosimeters should be performed when:
      • Lead aprons are worn. In this instance, collar badges should be worn instead of chest badges. If no lead is worn, chest badges will be assigned instead.
      • Fluoroscopy is used while personnel are in a control room or behind shielding (not including lead aprons).
      • X-rays are used in a veterinary setting where animals need to be held.
      • Personnel must be in the same room as an open beam x-ray device.
      • Workers in a different area with a similar function have been determined to need dosimetry.
    • Dosimeters are required when:
      • Fluoroscopy is used while personnel are present.

 

Exposure History

The exposure history of all monitored personnel is maintained by the RSS. Any RW who receives a dosimeter can request a copy of their record from the RSS or access it online.

 

BIOASSAYS

 

Iodine

A bioassay shall be performed immediately when greater than 0.100 µCi of material may have entered the body through absorption, ingestion, injection or other accidental deposition.

A bioassay shall be performed within 10 days for the following:

  • When greater than 1.0 mCi of material is processed in an open room,
  • When greater than 10.0 mCi of material is processed in an operating fume hood.
 
Tritium

A bioassay shall be performed within 7 days for the following:

  • When greater than 0.250 mCi of material may have entered the body through absorption, ingestion, injection or other accidental deposition,
  • When greater than 10 mCi of material is processed in an open room, or
  • When greater than 100 mCi of material is processed in an operating fume hood.

 

Page last updated on January 17, 2024.