Iron-59

 

Physical Characteristics:

  • Half-life: 44.6 days
  • Emmissions:
  • Beta particles: 0.273 MeV (46%) and 0.466 MeV (53%) maximum energies with average energies of 0.081 MeV and 0.149 MeV respectively.
  • Gamma rays: 1.099 MeV (56%) and 1.292 MeV (44%).
  • Beta Maximum Range: ~ 100 cm in air; 0.14 cm in tissue; 0.12 cm in plexiglas
  • Fraction transmitted through the dead layer of the skin: 0.95
  • Half-Value Layer: 15 mm lead
    The half-value layer is the amount of material required to reduce the radiation intensity by 50%.

Dose and Shielding:

  • Gamma dose rate (deep tissue dose) at 30 cm: 7.0 mrem/hour/mCi (for an unshielded point source)
  • Beta dose rate to the skin at 30 cm: 130 mrem/hour/mCi (for an unshielded point source)
  • Dose rate to epidermal basal cells from skin contamination of 1 μCi/cm2: 3593 mrem/hour
  • Shielding: Generally, lead is the preferred shielding material for Fe-59 for lower activity operations. However, it may be desirable to use a combination of plexiglas and lead/steel as shielding when working with multi-millicurie amounts to minimize the amount of bremsstrahlung produced by the betas. In such a case, plexiglas should be placed closest to the source as primary shielding, and lead should be used outside the plexiglas as secondary shielding. Annual Limit on Intake (ALI): 800 microcuries via ingestion and 300 via inhalation. The intake of one ALI will produce a dose of 5 rem.

Detection:

A sodium iodide crystal scintillation detector is the preferred method for detecting Fe-59. Additionally a G-M detector will readily detect Fe-59 contamination, although liquid scintillation counting is also an acceptable method for detecting removable contamination.

Precautions:

High localized doses are possible while handling Fe-59 and as a result of skin contamination. Reduce doses by wearing safety glasses (for shielding the eyes), using remote handling tools such as tongs, using shielding extensively to shield storage and experimental containers and work areas, and performing thorough and frequent surveys of the work area, clothing and the body. Radiation Monitoring Requirements: Radiation monitoring badges must be worn by any person who uses open sources of Fe-59 in amounts of 0.5 mCi or more for extended operations (applies to most operations other than simple aliquoting from a stock vial).

Waste Disposal:

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

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