Radionuclide Fact Sheet

CHROMIUM - 51

Symbol: ⁵¹Cr

States/Forms: Soluble

Physical Characteristics

Radioactive Half Life (T_½): 27.7 days
Decay Type: Electron (e^-) capture, Gamma, X-ray
Maximum Energy Emissions:
- 0.752 MeV (e^- capture)
- 0.320 MeV (Gamma)
- 0.005 MeV (X-ray)

Hazard Category

Radiological Characteristics

Critical organs: Liver (25%), bone (5%), lower large intestine, and kidneys
Routes of intake: Ingestion, inhalation, skin contamination (absorption).
Internal exposure and contamination: Primary radiological concerns with ⁵¹Cr.
External exposure: Primary radiological concern with ⁵¹Cr.

Dosimetry

Film badges and dosimeter rings are required if 10 millicuries (mCi) or more is to be handled at a given time, or if 5 mCi levels are handled frequently.

Bioassay Requirements

External Radiation Hazards and Shielding

The exposure rate at 1 cm from 1 mCi is 180 millirads per hour (mR/hr). The exposure rate varies directly with activity and inversely with the square of the distance. ¼ inch of lead shielding should be used when working with concentrations > 1 microcurie (μCi). ½ inch of lead shielding should be used when working with concentrations > 10 μCi.

Hazards if Internally Deposited

ALI (Annual Limit of Intake):

DAC (Derived Air Concentration):

Survey Instrumentation

Problems and Precautions

Lead shielding should be used when working with or storing 10 mCi of ⁵¹Cr or greater. Stock solution vials should be handled in shields or with tongs or forceps.
Lab coats and protective gloves should always be worn when working with ⁵¹Cr to keep skin free from contamination, and gloves should be changed often.
Survey frequently.
Waste should be segregated to those with half-lives from 15 days to less than 60 days.