Nuclide reference
Cs-131 — Caesium-131
The half-life of Cs-131 is 9.689 d. Main decay mode: electron capture to Xe-131 (100%).
Identification
- Element
- Caesium (Cs)
- Atomic number Z
- 55
- Mass number A
- 131
- State
- Radioactive
Key quantities
- Half-life
- 9.689 d
- Specific activity
- 3.806e+15 Bq/g
- Gamma constant Γ (H*(10))
- 0.01673 µSv·m²/(MBq·h)
- Dose rate, 1 GBq at 1 m
- ≈ 16.7 µSv/h
- A1 / A2 for transport (SSR-6, НП-053-16)
- 30 TBq / 30 TBq
- D-value (НП-067-24)
- 20 TBq
Decay modes
- electron capture → Xe-131 — 100 %
Main gamma lines
| Energy, keV | Yield, % |
|---|---|
| 29.778 · X-ray line | 39.78 |
| 29.458 · X-ray line | 21.48 |
| 33.625 · X-ray line | 7.24 |
| 4.09585 · X-ray line | 4.602 |
| 4.47707 · X-ray line | 4.25 |
| 33.563 · X-ray line | 3.734 |
| 34.408 · X-ray line | 1.527 |
| 34.408 · X-ray line | 0.783 |
| 5.1312 · X-ray line | 0.6515 |
| 3.67511 · X-ray line | 0.5849 |
Lines of the bare nuclide (ENDF/B-VIII.0), without daughter ingrowth.
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.