The University of Iowa

Radionuclide Safety Guideline for Cr-51

Physical Data

  • Radiation: Gamma - 320 keV (9.8% abundance)
  • X-ray: 5 keV (22% abundance)


  • Physical: 27.7 days
  • Biological: 616 days
  • Effective: Bound - 26.6 days; (whole body)


  • Theoretically infinite in air (unshielded)

External, Skin & Eye Hazard

  • Is an external exposure hazard. Unshielded exposure rate from a 1mCi point source at a distance of 1 cm is 160 mrem/hour.

Internal Hazard

  • Critical Organ: Lower Large Intestine (LLI)


  • 0.90 cm of lead will reduce original exposure intensity greater than 96%

Safety Guidelines

  • Whole body and ring dosimeters are required to be worn by individuals working with > 1 mCi amount of Cr-51.
  • Wear a lab coat and disposable gloves when working with Cr-51. Change gloves frequently.
  • Avoid direct eye contact – wear safety glasses to avoid splashing Cr-51 into eyes.
  • Store >1mCi amounts of Cr-51 source vials and solutions behind lead shields.

updated 1/2013