27.7 Days



Beta Energy

320 keV

Travel distance

  • Air: 1105 feet or 337 m
  • Lead: 0.5 in (99% reduction) or 1.27 cm

Annual Intake Limit

  • Inhalation: 20,000 µCi
  • Ingestion: 40,000 µCi


  • Portable Survey Meters:
    • Geiger-Mueller with NaI scintillation probe
  • Wipe Test: Liquid Scintillation Counting


None required – mCi quantities not an external radiation hazard

Dosimeter Monitoring

  • Wear radiation dosimetry monitoring badges [body & ring] when handling 51Cr


  • Store 51Cr (including waste) behind lead shielding [1/4-1/2 inch thick]; survey (with GM meter) to check adequacy of shielding (accessible dose rate <2 mR/hr; should be background)
  • Avoid skin contamination [absorption], ingestion, inhalation, & injection [all routes of intake]
  • Use shielding to minimize exposure while handling 51Cr
  • Use tools to handle 51Cr sources and contaminated objects; avoid direct hand contact


  • Place the Lead shielding near a wall (not toward work area on the other side of the bench) away from the main flow of traffic in the lab. This applies to both work conditions and waste storage.
  • Check the radiation level in front of the shield to determine if additional lead should be added.
  • Dispose the waste as per USC radiation waste policies. Do not mix the waste with any other isotope.

Radiological Data

  • Radiotoxicity:
    • 0.145 mrem/uCi of 51Cr ingested [CEDE];
    • 0.334 mrem/uCi of 51Cr inhaled [CEDE]
  • Critical Organ:
    • Lower Large Intestine [LLI]
  • Intake Routes:
    • Ingestion, inhalation, injection, absorption
  • Radiological Hazard:
    • External & Internal exposure; contamination