Iodine-131 (I-131) - doe-hdbk-1106-97

DOE-HDBK-1106-97

IODINE-131 (I-131)

Iodine-131 is a gamma, X-ray and beta emitter. I-131 contamination may be detected by a thin-

window G-M probe or with liquid scintillation counting.

1. Maximum beta energies: 0.248 - 0.606 MeV.

2. Primary gamma energies: 0.364 MeV, 0.637 MeV and 0.284 MeV.

3. IAEA toxicity classification: Medium-high.

4. Physical half-life: 8 days.

5. Effective half-life (Teff): 7.6 days.

6. Critical organ: Thyroid gland.

7. Personnel monitoring: Dosimeter, thyroid scan for uptakes.

8. ALI:

0.05 mCi (2 x 106 Bq) by inhalation, daily clearance.

0.03 mCi (1 x 106 Bq) by ingestion.

9. Shielding: 2.3 mm of lead is the first half-value layer.

10. Other considerations for iodine compounds:

Volatilization of iodine is the most significant hazard.

Simply opening a vial of sodium iodide (NaI) at high-radioactive concentrations

can cause minute droplets to become airborne.

Solutions containing iodide ions should not be made acidic nor stored frozen;

both lead to formation of volatile elemental iodine.