Radium-224
Ra-224 · Radium, Z = 88, A = 224
At 5.94e+15 Bq/g — 1.61e+5 Ci/g — a gigabecquerel of Ra-224 amounts to 168 ng, which is why activity rather than mass is how anyone states the quantity. Radium-224 decays by alpha decay with a half-life of 3.6316 days, falling to 26.29% of today's activity in a week and 2.9e-6% in three months.
Alpha emission is led by 5.685 MeV at 94.92%, one of 2 recorded lines. None of it reaches through skin, so the limit here is intake, not external dose.
Decay is the only handle: a week leaves 26.29% of today's activity and three months leaves 2.9e-6%, with ten half-lives at 36.3 days and a mean life of 5.24 days per atom.
Half-life 3.6316 days, 5.94e+15 Bq/g, and no line recorded
| Half-life | 3.6316 days (3.138e+5 s) |
| Decay mode | alpha decay |
| Specific activity | 5.94e+15 Bq/g (1.61e+5 Ci/g) |
2 alpha lines, strongest 5.685 MeV
2 recorded lines from 5.449 to 5.685 MeV, the strongest 5.685 MeV at 94.92% of 99.98% total alpha emission.
| Energy (MeV) | Emission probability (%) |
|---|---|
| 5.6854 | 94.92 |
| 5.4486 | 5.06 |
Activity over months and years
Ten half-lives is 36.3 days — a storage problem rather than a disposal one, with 5.3e-29% of today's activity still there after a year. The mean life 1/λ is 5.24 days.
| Elapsed | Fraction remaining |
|---|---|
| 1 half-life | 50.0 % |
| 2 half-lives | 25.0 % |
| 5 half-lives | 3.13 % |
| 10 half-lives | 0.0977 % |
| Time to fall to 10 % of today's activity | 12.1 days |
| Time to fall to 1 % | 24.1 days |
| Time to fall to 0.1 % | 36.2 days |
Limits — intake, not external dose
- Alpha reaches nothing through skin — Ra-224 is an intake problem, not an external one.
- What every sheet leaves out, internal dose included.
Decay and mass calculators for Ra-224
Other Radium nuclides: Ra-223, Ra-226, Ra-228
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.