Sulfur-35

Physical Characteristics:

• Half-life: 87.6 days
• Emissions: Beta particles with a maximum energy of 167 keV and an average energy of 49 keV.
• Maximum Range in Air: 24 cm in air; 0.030 cm in tissue.
• Fraction transmitted through the dead layer of the skin: 0.12

Dose:

• Dose rate to the skin at 10 cm: 625 mrad/hour/mCi
  (for an unshielded point source)
• Dose rate to epidermal basal cells from skin contamination of 1 mCi/cm2:1460 mrad/hour

Shielding: 

• ¼ inch Plexiglas/acrylic/lucite/plastic/wood
• Do not use lead foil or sheets as primary barrier! Penetrating bremsstrahlung x-ray will be produced!
• Use lead sheets or foil to shield bremsstrahlung x-rays only after low density Plexiglas/acrylic/lucite/wood shielding.

Annual Intake Limits (ALI)

• 10 millicuries via ingestion for most compounds of sulfur.
  Note: 1.0ALI = 5,000 mrem CEDE

Detection:

• Survey meter equipped with a G-M pancake or thin-window probe can be used to detect the betas from the S-35. Typical efficiency for a G-M pancake survey meter is between 4% and 6%.
• A liquid scintillation counter should be used to detect removable S-35 contamination on wipe tests smears. Typical efficiency for a LSC to detect S-35 is greater than 85%.
• Whole Body dosimeter: Not required
• Finger dosimeter: Not required

Precautions:
35S-labeled methionine/cysteine compounds can volatilize. Stock solutions and thawed materials should be opened within a fume hood. Activated charcoal can be used to trap contamination within equipment such as incubators. Contact EHS for further information. Low-level S-35 contamination cannot be easily detected with a G-M 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 the work space does not contain low-level removable contamination.

Waste Disposal: Call radiation safety office