Section 15: Safety and Handling of Beta Emitters

A. Beta Emitters Commonly Used on Campus

  • The beta emitters most commonly used on campus are H-3, C-14, S-35, Ca-45, and P-32. The maximum energies of the betas emitted and their ranges in air are given in the table below:

    Radionuclide Emax (MeV) Range in Air (Cm)
    3H 0.018 Less than 1
    14C 0.155 28
    35S 0.167 33
    45C 0.254 51
    32P 1.71 635

B. Most Hazardous, Commonly Used Beta Emitter

  • The most hazardous, commonly used beta emitter on campus is P-32. Phosphorous-32 is used extensively in research and must be handled carefully. Phosphorous-32 emits beta particles with maximum energies of 1.71 Mev and average energies of 0.57 Mev.
    1. Significant dose rates may be experienced when handling P-32. For example, the dose rate at the surface of a 1 ml solution containing 1 mCi of phosphorous-32 is approximately 13 rem/hr. The average dose rate to the hand while it is in contact with a glass shipment vial containing 1 mCi of P-32 is 439 mrem/hr. As a final example, the average dose rate at a 10 cm distance from the side of a glass shipment vial containing 1 mCi of P-32 is 5 mrem/hr.
    2. Tritium, carbon-14, sufur-35, and calcium-45 are not external radiation hazards.

C. Dose Rates

  • Estimates of dose rates should be conducted before handling high-energy beta emitters, such as P-32. The dose rate estimates can be calculated using the equations below. These equations were taken from The Health Physics and Radiological Health Handbook (1984).
  • Equation 1 Dose Rate (rads/hr) at One Centimeter from a Point Source
    • DR1cm is approximately equal to 200 x A
    • Where DR1cm = the dose rate at 1 cm distance from the radioactive point source (rads/hr); and A is the quantity of radioactive material (mCi)

  • Equation 2 Dose Rate (rads/hr) in a Solution
    • Dsol is approximately equal to 1.12 EC/p
    • Where Dsol = the dose rate in solution (rads/hr);
    • E = the average beta particle energy (Mev);
    • C = the concentration of radioactive materials (?Ci/cm3);
    • And p is the density of the solution (g/cm3)

  • Note: The dose rate is about one-half this value at the surface of the solution.

D. General Practices and Guidelines

  • Follow the general lab practices and guidelines below to reduce radiation exposures:
    1. Always keep radioactive and non-radioactive work separated as far as possible, preferably by maintaining rooms used solely for radioactive work.
    2. Always work over a spill tray and in a ventilated enclosure (except with small (<1 mCi) quantities of 3-H, 35-S, or 14-C compounds in a non-volatile form in solution).
    3. Always use the minimum quantity of radioactivity compatible with the objectives of the experiment.
    4. Always wear protective clothing, safety glasses, and gloves when handling radioactive materials.
    5. Always wash your hands and monitor yourself before leaving an area where radioactive materials are handled or stored.
    6. Always work carefully and monitor the working area regularly to avoid ruining experiments by accidental contamination.
    7. Always label containers of radioactive material clearly, indicating radionuclide, total activity, compound, and date.
    8. Never eat, drink, smoke, or apply cosmetics in an area where unsealed radioactive materials are handled or stored.
    9. Never use ordinary handkerchiefs to clean items or surfaces; use paper tissues and dispose of them as radioactive waste.
    10. Never work with cuts or breaks in the skin unprotected, particularly on the hands or forearms.
    11. Never pipette radioactive solutions by mouth.
    12. In the event of a spill, it is essential to minimize the spread of contamination by adhering to the following steps:
      • Cordon off the suspected area of contamination. Ascertain, if possible, the type of contamination, i.e. the nuclide(s) involved (as it may be necessary to use breathing apparatus, protective clothing, or other equipment).
      • Determine the area of contamination by monitoring, after taking the necessary precautions.
      • Decontaminate the area in convenient sectors by wiping and scrubbing, starting from the outer edge.
      • Ensure that a sector is clean by monitoring before moving to another sector.

    13. Use tongs or other remote handling equipment, where appropriate, to minimize dose to the extremities.

E. Specific Practices

  • Specific practices to follow when handling P-32 and volatile radioactive materials are listed below. These practices are in addition to those stated in Item D.
    1. Phosphorous-32
      • Place containers of P-32 and materials/items contaminated with P-32 such as pipettes into Plexiglas or Lucite containers that are about 1 cm thick.
      • If the measured exposure rate from a container with P-32 exceeds 1mR/hr at 1 ft, additional shielding in the form of 1/16-1/8 in. lead sheets should be used. This shielding should be placed exterior to the Plexiglas.
      • Notes:
        • Baylor University Machine Shop personnel can prepare blocks of Plexiglas with holes drilled to fit test tubes, vials, beakers, and other containers.
        • Additional information on handling P-32 safely is provided in the Appendix to this manual.

    2. Volatile Radioactive Material
      • Handle volatile radioactive materials in fume hoods that are operating properly.
      • Volatile radioactive materials include, but are not limited to, those compounds that are labeled with H-3, S-35, C-14, I-125, and I-131.

    3. Radioiodine (I-125, I-131)
      • Handle radioiodine (I-125, I-131) in quantities greater than 10 mCi in fume hoods with activated charcoal filters.
      • Note: The above steps and many of those in Item D above will reduce the potential for ingestion and inhalation of radioactive materials.