Radium-228
Ra-228 · Radium, Z = 88, A = 228
Radium-228 decays by beta-minus decay, half-life 5.75 years. Specific activity is 1.01e+13 Bq/g (273 Ci/g), so a gigabecquerel comes to 99.1 µg — weighable, but on an analytical balance. Over a year the activity falls to 88.64%, and over forty years to 0.81%.
At 1.01e+13 Bq per gram, a 1 kBq aliquot of Ra-228 is 99.1 pg — the quantity that has to be recovered, dissolved and counted, because this dataset carries no photon, beta or alpha line for it above the reporting thresholds.
Decay is the only handle: a year leaves 88.64% of today's activity and forty years leaves 0.81%, with ten half-lives at 57.5 years and a mean life of 8.30 years per atom.
Half-life 5.75 years, 1.01e+13 Bq/g, and no line recorded
| Half-life | 5.75 years (1.815e+8 s) |
| Decay mode | beta-minus decay |
| Specific activity | 1.01e+13 Bq/g (273 Ci/g) |
Activity over decades and centuries
Ten half-lives is 57.5 years, which puts decay storage out of reach: 0.81% survives forty years. The mean life 1/λ, the quantity that enters an integrated dose, is 8.30 years.
| 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 | 19.1 years |
| Time to fall to 1 % | 38.2 years |
| Time to fall to 0.1 % | 57.3 years |
Limits of these figures
- What every sheet leaves out, internal dose included.
Decay and mass calculators for Ra-228
Other Radium nuclides: Ra-223, Ra-224, Ra-226
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.