CHARACTERISTICS OF COMMONLY USED RADIONUCLIDES
Tritium is a low-energy beta emitter and cannot be monitored directly with a thin-window G-M
probe. Monitoring is normally performed by taking a swipe of the area and counting the swipe in
a liquid scintillation counter.
1. Maximum energy: 0.018 MeV (average energy is 0.006 MeV or about 1/3 the
2. Maximum range in air: 1/4 inch (6 mm).
3. Maximum range in water: 6 x 10-3 mm.
4. International Atomic Energy Agency (IAEA) toxicity classification: Low.
5. Physical half-life (T1/2): 12.35 years.
6. Effective half-life (Teff): 10 days (the time it takes for of the material to be eliminated
from the body by both biological processes and radioactive decay).
7. Critical organ: Whole body (the part of the body where the most limiting dose is
8. Personnel monitoring: Bioassay - urinanalysis, NOT detected with a dosimeter
(thermoluminescent dosimeter or film).
9. Annual Limit of Intake (ALI):
Tritiated water: 80 mCi (3 x 109 Bq) by inhalation or ingestion.
10. Shielding: None (the low-energy beta is not very penetrating).
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