HP-25: Tritium

Introduction

Hydrogen-3 is a commonly used radionuclide with a half-life of 12.3 years, emitting only beta particles with a maximum energy of 0.019 MeV (Million Electron Volts) and an average energy of 0.0057 MeV. The beta particles from H-3 travel a maximum of 6 mm in air.

Concerns

The major concern with using H-3 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 H-3. The maximum permissible body burden to the whole body is 1 mCi.

CONTACT
Office Location: 37 Lee Street - 105B
Phone: 508-831-4603

Shielding

Glass and plastic are the best shields for beta particles from H-3.

Detection

A tiny drop of contamination containing H-3 can be easily detected with a wipe test from a liquid scintillation counter. A Geiger counter will not detect the presence of H-3.

Equipment/Supplies

The following equipment and supplies must be available:

  • A liquid scintillation detector
  • Disposable latex or plastic gloves
  • full-length lab coat
  • containers for radioactive waste
  • pipettes dedicated to the use of H-3
  • 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 H-3 handling
  • Full-length lab coats must be worn by all persons who handle H-3
  • Protect the skin of your hands from becoming contaminated from spills by wearing two pairs of disposable gloves
  • Never pipette H-3 by mouth
  • Only use pipettes which have been dedicated to your specific use of H-3; 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 H-3, 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 waste temporarily in specially marked containers
  • Wash your hands thoroughly.

Other Information

Physical Data

  • Beta Energy: 18.6 keV (maximum)
  • 5.7 keV (average) (100% abundance)
  • Physical Half-Life: 12.3 years
  • Biological Half-Life: 10-12 days
  • Effective Half-Life: 10-12 days1
  • Specific Activity: 9640 Ci/gram
  • Maximum Beta Range in Air: 6 mm
  • Maximum Beta Range in Water: 0.006 mm
  • Penetrability in Matter or Tissue: Insignificant2

1Forcing liquids to tolerance (3-4 liters/day) will reduce the effective half-life of tritium by a factor of 2 or 3. (Relatively easy to flush out of system with fluids.) 20% of beta particle energy transmitted through dead layer of skin

Radiological Data

  • Least radiotoxic of all radionuclides
  • Critical Organ: Body Water or Tissue
  • Routes of Intake: Ingestion, Inhalation, Puncture, Wound, Skin Contamination (Absorption)
  • External exposure from weak tritium beta energy - not a radiological concern
  • Internal exposure & contamination are primary radiological concerns
  • Committed Dose Equivalent (CDE): 64 mrem/mCi (ingested), 64 mrem/mCi (inhaled), 64 mrem/mCi (puncture)
  • Committed Effective Dose Equivalent (CEDE): 90 mrem/mCi (ingested), 63 mrem/mCi (inhaled)
  • Annual Limit on Intake (ALI):1 80 mCi (ingestion or inhalation)
  • Skin Contamination Exposure Rate: 57900 mrad/hr/mCi (contact)2
  • Rule of Thumb: 0.001 uCi/ml of tritium in urine sample is indicative of a total integrated whole body dose of approximately 10 mrem (average person) if no treatment is instituted (i.e., flush with fluids); [NCRP-65, 1980]

1[1.0 ALI = 80 mCi (Tritium = 5000 mrem CEDE) 2Exposure rate to dead layer of skin only (Skin contamination of 1.0 uCi/cm2 = 0 mrad/hr dose rate to basal cells)

Shielding

None required.

Survey Instrumentation

  • CANNOT detect tritium using a G-M or NaI survey meter
  • Liquid scintillation counter (indirect) is the only monitoring method

Dosimetry

Whole Body Badge or Finger Rings: Not Needed (beta energy too low)

Radioactive Waste

Solid, liquids, scintillation vials, pathological materials, animal carcasses

Regulatory Compliance Information

  • Derived Air Concentration (DAC):2.0E-5 uCi/cc (occupational)
  • Airborne Effluent Release Limit: 1.0E-7 uCi/cc1
  • If this concentration was inhaled continuously for over one year the resulting TEDE would be 50 mrem
  • Controlled Area Removable Contamination Limit: 2,200 dpm/100 cm2
  • Urinalysis: Required when handling greater than or equal to 100 mCi tritium

1Applicable to the assessment & control of dose to the public (10CFR20.1302)

General Radiological Safety Information

  • Inherent Volatility (at STP): Substantial
  • Experimental uses include: total body water measurements & in-vivo labeling of proliferatory cells by injection of tritium-labeled compounds (i.e., thymidine)
  • Tritium labeling is also used in a variety of metabolic studies
  • Oxidation of tritium gas in air is usually slow (< 1% per day)
  • Absorption of tritium inhaled in air is much less when it is present as elemental tritium than as tritiated water (HTO)
  • Tritium penetrates the skin, lungs, and GI tract either as tritiated water or in the gaseous form
  • As gaseous hydrogen, tritium entering the lung or GI tract is completely absorbed and rapidly dispersed within the body
  • Some tritium is incorporated into cellular components and has a long turnover rate
  • Forcing fluids reduces integrated internal exposures from tritium
  • Monitor for tritium contamination using only wipe-testing (bench tops, floors, refrigerator/freezer handles, phone, etc.)
  • Always wear a lab coat & disposable gloves when handling tritium
  • Skin contamination, inhalation, ingestion, or absorption through the skin is assumed to be completely and instantaneously absorbed and rapidly mixed with total body water
  • The volume of total body water (standard man) is 42,000 mL
  • The concentration of 3H in urine assumed to be the same as in total body water
  • Detection limit of tritium in urine: 1.08E-5 uCi/mL (approximately)
  • For a continuous inhalation exposure at a rate of 1/365 of an ALI per day, the equilibrium concentration of tritium in urine is 0.073 uCi/mL [NOTE : 1/365 of 80 mCi (ALI) = 219 uCi]
  • The predicted concentration activity normalized to unit intake from inhalation is 2.204E-5 uCi/mL/uCi of tritium