Nuclide reference
Th-228 — Thorium-228
The half-life of Th-228 is 1.912 years. Main decay mode: α decay to Ra-224 (100%).
Identification
- Element
- Thorium (Th)
- Atomic number Z
- 90
- Mass number A
- 228
- State
- Radioactive
Key quantities
- Half-life
- 1.912 years
- Specific activity
- 3.034e+13 Bq/g
- Gamma constant Γ
- —
- A1 / A2 for transport (SSR-6, НП-053-16)
- 0.5 TBq / 0.001 TBq
- D-value (НП-067-24)
- 0.04 TBq
Decay modes
- α decay → Ra-224 — 100 %
Main gamma lines
| Energy, keV | Yield, % |
|---|---|
| 238.632 (Pb-212) | 43.86 |
| 2,614.51 (Tl-208) | 36.07 |
| 583.187 (Tl-208) | 30.73 |
| 77.109 (Pb-212) · X-ray line | 16.94 |
| 74.817 (Pb-212) · X-ray line | 10.12 |
| 510.77 (Tl-208) | 8.171 |
| 727.33 (Bi-212) | 6.708 |
| 860.557 (Tl-208) | 4.519 |
| 240.986 (Ra-224) | 4.122 |
| 84.373 | 1.22 |
Includes daughter nuclides in equilibrium: Ra-224, Rn-220, Po-216, Pb-212, Bi-212, Tl-208 (yield per decay of Th-228); the emitting nuclide is in brackets. Equilibrium is reached in about 26 d. In transient equilibrium a daughter's activity exceeds the parent's, so a yield can be above 100%. Equilibrium with radon requires a sealed source.
Alpha and beta particles
| Radiation | Energy, keV | Yield, % |
|---|---|---|
| α | 5,423.2 | 72.2 |
| 5,685.4 (Ra-224) | 95.42 | |
| 6,288.1 (Rn-220) | 100.4 | |
| 6,778.3 (Po-216) | 100.5 | |
| β⁻, E max | 331.27 (Pb-212) | 83.59 |
| 569.9 (Pb-212) | 11.97 | |
| 2,252.1 (Bi-212) | 55.7 | |
| 1,801.3 (Tl-208) | 17.75 |
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.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.