Introduction

Phosphorus-33 is becoming more commonly used radionuclide with a half-life of 25.4 days, emitting only beta particles with a maximum energy of 0.249 MeV and an average energy of 0.083 MeV. The beta particles from P-33 travel a maximum of 46 cm in air.

Concerns

The major concern with using P-33 is that it cannot be easily monitored during its use, therefore, special precautions are needed to keep the work environment clean. The regular use of wipe testing is the only way to insure that your work space is not contaminated. Contamination on the skin will not likely cause a significant dose to the dead layer of skin, however, it could lead to the internal absorption of P-33. The maximum permissible body burden to the whole body is 3 mCi.

Shielding

Glass and plastic are the best shields for beta particles from P-33.

Detection

A tiny drop of contamination from P-33 can be easily detected with a wipe test from a Liquid Scintillation Counter. Most Geiger Counters will not efficiently detect the presence of P-33.

Equipment/Supplies

The following equipment and supplies must be available:

  • A Liquid Scintillation Detector
  • Disposable latex or plastic gloves
  • A full-length lab coat
  • Radioactive waste receptacle
  • Pipettes dedicated to the use of P-33
  • Commercial decontaminate

Safety Rules

If the following safety precautions are used, personnel radiation exposure will be as low as reasonably achievable.

  • Designate a specific area of the lab for P-33 handling
  • Full-length lab coats must be worn by all persons who handle P-33
  • Protect your hands from becoming contaminated from spills by wearing two pairs of disposable gloves
  • Never pipette P-33 by mouth
  • Only use pipettes which have been dedicated to your specific use of P-33
  • Pipettes will easily become contaminated and therefore, should not be shared with others
  • If you have reason to believe that your gloves are contaminated, immediately dispose of them in the radioactive waste container

Post-Use Procedures

  • Conduct a wipe test and count the wipes in a Liquid Scintillation counter
  • Check all equipment, centrifuges, water baths for contamination
    • If any contamination is found, use a commercial radiation contamination remover with paper towels to clean up the equipment
    • Place the towels in the radioactive waste receptacle
  • If contamination cannot be removed, place a "radiation" label on the equipment indicating that it is P-33, maximum cpm found, and the date you measured the level
  • Check the work bench and floor
    • If contamination is found, it can usually be removed easily
    • If it cannot be removed, contact the RSO at rso@wpi.edu to obtain shielding materials
    • Inform your fellow lab workers if any unremovable contamination is found
  • Check the normal trash container to make sure no radioactive waste has been accidentally placed there
  • Store the waste temporarily in containers marked with labels "Radioactive Waste-Do Not Empty"
  • Wash your hands thoroughly

Other Information

Physical Data

  • Beta energy: 0.249 keV (maximum, 100% abundance)
  • 0.085 keV (average)
  • Physical half-life: 25.4 days
  • Biological half-life: 19 days (40% of intake; 30% rapidly eliminated from body, remaining 30% decays)
  • Effective half-life: 24.9 days (bone)
  • Specific activity: 1,000 - 3,000 Ci/millimole
  • Maximum beta range in air: 89 cm
  • Maximum range in water/tissue: 0.11 cm
  • Maximum range in plexiglas/lucite/plastic: 0.089 cm
  • Half-Value Layer (HVL): 0.30 mm (water/tissue)

Radiological Data

  • Critical organ (biological destination) (soluble forms): Bone marrow
  • Critical organs (insoluble forms or non-transportable P-33 compounds): Lung (inhalation) and G.I. tract/lower large intestine (ingestion)
  • Routes of intake: Ingestion, inhalation, puncture, wound, skin contamination (absorption)
  • Internal exposure and contamination are the primary radiological concerns
  • Committed Dose Equivalent (CDE): 0.5 mrem/mCi (inhalation)
  • Skin contamination dose rate: 2,910 mrem/hr/uCi/cm2 (7 mg/cm2 or 0.007 cm depth in tissue)
  • Fraction of P-33 beta particles transmitted through the dead skin layer is about 14%
  • Tissues with rapid cellular turnover rates show higher retention due to concentration of phosphorus in the nucleoproteins.
  • P-33 is eliminated from the body primarily via urine
  • Phosphorus metablolism: 30% is rapidly eliminated from body
  • 40% has a 19-day biological half-life
  • 60% of P-33 (ingested) is excreted from body in first 24 hrs

Shielding

Not required; however low density material is recommended, e.g., 3/8" thick plexiglas, acrylic, lucite, plastic or plywood

Survey Instrumentation

  • GM survey meter with a pancake probe
  • Liquid scintillation counting of wipes may be used to detect removable surface contamination

Dosimetry

  • Not required, since they do not detect this low energy nuclide
  • It is recommended, however, that dosimetry should be worn when handling radioisotopes of any nature

General Precautions

  • Inherent volatility (STP): Insignificant
  • Skin dose and contamination are the primary concerns.
  • Drying can form airborne P-33 contamination.
  • Monitor work areas for contamination, using smears or wipes to check for removable contamination.