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Isotopes: Iron 55


Physical Characteristics:
  • Half-life: 2.70 years
  • Emissions: Principal emissions are a 6 keV x-ray and 5.2 keV [average] Auger electrons.
  • Electron Maximum Range: 0.15 cm in air; 0.0 cm in tissue
Dose and Shielding:
  • Dose rate to the skin at 10 cm: negligible
  • (for an unshielded point source)
  • Dose rate to basal cells from skin contamination of 1 μCi/cm2: 59 mrem/hr
  • Shielding: None needed, when used in millicurie quantities, under normal laboratory operations.
  • Annual Limit on Intake (ALI): 2,000 microcuries via inhalation, and 9,000 microcuries via ingestion. The intake of one ALI will produce a dose of 5 rem.
Detection:

Liquid scintillation counting is the preferred method for detecting Fe-55 contamination, although a low energy sodium iodide crystal scintillation detector will also detect Fe-55 with a lower efficiency. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that the work space does not contain low-level removable contamination

Precautions:

External radiation from Fe-55 is low energy and does not normally present an external exposure hazard. Low-level Fe-55 contamination is not readily detected with a survey meter, and special precautions are needed to keep the work environment clean. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that your work space does not contain low-level removable contamination. Radiation Monitoring Requirements: Radiation monitoring badges are not required for Fe-55 users.

Waste Disposal:
  • Solid Wastes: through the Off-Site Radioactive Waste Disposal Program.