Nuclide reference
Fr-222 — Francium-222
The half-life of Fr-222 is 14.2 min. Main decay mode: β⁻ decay to Ra-222 (100%).
Identification
- Element
- Francium (Fr)
- Atomic number Z
- 87
- Mass number A
- 222
- State
- Radioactive
Key quantities
- Half-life
- 14.2 min
- Specific activity
- 2.207e+18 Bq/g
- Gamma constant Γ
- —
- D-value (НП-067-24)
- —
Decay modes
- β⁻ decay → Ra-222 — 100 %
Main gamma lines
| Energy, keV | Yield, % |
|---|---|
| 206.17 | 50 |
| 111.11 | 13.1 |
| 88.473 · X-ray line | 3.513 |
| 324.31 (Ra-222) | 2.893 |
| 85.76 · X-ray line | 2.151 |
| 242.11 | 1.95 |
| 130.98 | 0.625 |
| 190.24 | 0.595 |
| 1,060.33 | 0.46 |
| 707.54 | 0.445 |
Includes daughter nuclides in equilibrium: Ra-222, Rn-218, Po-214 (yield per decay of Fr-222); the emitting nuclide is in brackets. Equilibrium is reached in about 4.4 min. 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 | 6,559 (Ra-222) | 101.2 |
| 6,241 (Ra-222) | 3.185 | |
| 7,129.2 (Rn-218) | 104.3 | |
| 7,686.8 (Po-214) | 104.4 | |
| β⁻, E max | 1,710.7 | 54 |
| 1,916.9 | 38 | |
| 2,028 | 3 | |
| 1,785.9 | 1.7 |
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.