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IODINE - 125
(125I)
| Physical Half-life: | 60.14 days |
| Radiations: | x/gamma 35 keV |
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| External Exposure: | External hazard when mCi quantities
are present. Radiation exposures from 1.0 mCi source are 62.4 mR/hr and
0.156 mR/hr at 5 cm & 100 cm, respectively. |
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| Biological Data: |
ALI | 0.04 mCi (ingestion), 0.06 mCi
(inhalation), thyroid |
| Biological half-life |
138 days |
| Effective half-life |
42 days |
| Critical Organs |
Thyroid |
| Bioassay |
Thyroid Scans |
| Shielding: |
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HVL 0.017 mm of lead; TVL 0.056 mm of lead |
Monitoring
& Efficiency |
LSC (Eff. ~50%)
Gamma Counter (Eff. 50-90%)
Low Energy Gamma (Scintillation) Meter (Eff. 50-90%) |
Special Considerations
- Work with volatile 125Fe (e.g. NaI) must be done in an
approved fume hood.
- Use a breathing zone monitor when working with 1.0 mCi or more of
volatile radioiodine or 10.0 mCi or more of nonvolatile radioiodine.
- Survey the work area immediately following any iodination. Document
survey results. Send a copy of the survey results to the Radiation Safety
Officer if 50 mCi or more are used.
- Thyroid bioassay is required ater using greater than or equal to 100
uCi of volatile 125I or greater than or equal to 1.0 mCi of
125 bound to a nonvolatile compound. Bioassay must be done
within 10 days after receipt of the iodine.
- To minimize volatilization avoid acidic solutions. Do not store NaI
solutions in freezers. Seal waste containers on the completion of our
iodination.
- Wear a radiation badge when handling 1.0 mCi or more of
125I.
- Do not use GM survey meters to monitor for contamination as they are
not sensitive to contamination levels of concern.
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