Nuclide reference
I-131 — Iodine-131
The half-life of I-131 is 8.0252 d. Main decay mode: β⁻ decay to Xe-131 (98.92%).
Identification
- Element
- Iodine (I)
- Atomic number Z
- 53
- Mass number A
- 131
- State
- Radioactive
Key quantities
- Half-life
- 8.0252 d
- Specific activity
- 4.596e+15 Bq/g
- Gamma constant Γ (H*(10))
- 0.06596 µSv·m²/(MBq·h)
- Dose rate, 1 GBq at 1 m
- ≈ 66 µSv/h
- A1 / A2 for transport (SSR-6, НП-053-16)
- 3 TBq / 0.7 TBq
- D-value (НП-067-24)
- 0.2 TBq
Decay modes
- β⁻ decay → Xe-131 — 98.92 %
- β⁻ decay → Xe-131m — 1.085 %
Main gamma lines
| Energy, keV | Yield, % |
|---|---|
| 364.489 | 81.5 |
| 636.989 | 7.156 |
| 284.305 | 6.121 |
| 80.185 | 2.616 |
| 29.778 · X-ray line | 2.548 |
| 722.911 | 1.769 |
| 29.458 · X-ray line | 1.376 |
| 503.004 | 0.3594 |
| 325.789 | 0.273 |
| 177.214 | 0.269 |
Lines of the bare nuclide (ENDF/B-VIII.0), without daughter ingrowth.
Alpha and beta particles
| Radiation | Energy, keV | Yield, % |
|---|---|---|
| β⁻, E max | 606.31 | 89.6 |
| 333.81 | 7.23 | |
| 247.89 | 2.08 | |
| 303.87 | 0.645 |
For β⁻ the endpoint (maximum) energy of the spectrum is given. ENDF/B-VIII.0.
Related calculators
Other isotopes of this element
Reference data vs computed valuesHalf-life, gamma lines and D-value are reference data (ENDF/B-VIII.0, НП-067-24).Gamma constant Γ is H*(10) at 1 m computed from ICRP-107 spectra (NIST µ_en/ρ, ICRP-74 Table A.21) including short-lived progeny in equilibrium (e.g. Cs-137/Ba-137m, Ra-226 series); specific activity uses molar mass M ≈ mass number A.Dose rate example: point source, no shielding or scatter, Ḣ = Γ·A/r².K-series X-ray energies are from NIST SRD 128 (Deslattes et al., 2003): in ENDF/B-VIII.0 they are given to 1 % and shifted by up to 0.7 keV for heavy elements. L-series lines and all yields are ENDF/B-VIII.0.