Nuclide reference
Ac-225 — Actinium-225
The half-life of Ac-225 is 10 d. Main decay mode: α decay to Fr-221 (100%).
Identification
- Element
- Actinium (Ac)
- Atomic number Z
- 89
- Mass number A
- 225
- State
- Radioactive
Key quantities
- Half-life
- 10 d
- Specific activity
- 2.147e+15 Bq/g
- Gamma constant Γ
- —
- A1 / A2 for transport (SSR-6, НП-053-16)
- 0.8 TBq / 0.006 TBq
- D-value (НП-067-24)
- 0.09 TBq
Decay modes
- α decay → Fr-221 — 100 %
Main gamma lines
| Energy, keV | Yield, % |
|---|---|
| 440.45 (Bi-213) | 26.03 |
| 218.12 (Fr-221) | 11.38 |
| 14.7188 · X-ray line | 8.995 |
| 12.0208 · X-ray line | 8.836 |
| 10.642 | 8.5 |
| 1,567.09 (Tl-209) | 2.204 |
| 465.13 (Tl-209) | 2.139 |
| 117.211 (Tl-209) | 1.861 |
| 99.8 | 1 |
| 99.6 | 0.7 |
Includes daughter nuclides in equilibrium: Fr-221, At-217, Bi-213, Po-213, Tl-209, Pb-209 (yield per decay of Ac-225); the emitting nuclide is in brackets. Equilibrium is reached in about 23 h. In transient equilibrium a daughter's activity exceeds the parent's, so a yield can be above 100%.
Alpha and beta particles
| Radiation | Energy, keV | Yield, % |
|---|---|---|
| α | 5,830 | 50.7 |
| 6,341 (Fr-221) | 83.42 | |
| 7,066.9 (At-217) | 99.93 | |
| 8,375.9 (Po-213) | 98.14 | |
| β⁻, E max | 1,423 (Bi-213) | 66.03 |
| 982.56 (Bi-213) | 30.85 | |
| 1,827.6 (Tl-209) | 2.181 | |
| 644 (Pb-209) | 101.7 |
For β⁻ the endpoint (maximum) energy of the spectrum is given. ENDF/B-VIII.0.
Related calculators
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.