Gadolinium-148
Gd-148 · Gadolinium, Z = 64, A = 148
Gadolinium-148 decays by alpha decay, half-life 71.1 years. Specific activity is 1.26e+12 Bq/g (34.0 Ci/g), so a gigabecquerel comes to 795 µg — weighable, but on an analytical balance. Over a year the activity falls to 99.03%, and over forty years to 67.71%.
Alpha emission is led by 3.183 MeV at 100%. None of it reaches through skin, so the limit here is intake, not external dose.
Decay is the only handle: a year leaves 99.03% of today's activity and forty years leaves 67.71%, with ten half-lives at 711 years and a mean life of 103 years per atom.
Half-life 71.1 years, 1.26e+12 Bq/g, and no line recorded
| Half-life | 71.1 years (2.244e+9 s) |
| Decay mode | alpha decay |
| Specific activity | 1.26e+12 Bq/g (34.0 Ci/g) |
One alpha line at 3.183 MeV
One recorded line, 3.183 MeV at 100% — monoenergetic as far as this dataset goes.
| Energy (MeV) | Emission probability (%) |
|---|---|
| 3.1827 | 100 |
Activity over decades and centuries
Ten half-lives is 711 years, which puts decay storage out of reach: 67.71% survives forty years. The mean life 1/λ, the quantity that enters an integrated dose, is 103 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 | 236 years |
| Time to fall to 1 % | 472 years |
| Time to fall to 0.1 % | 709 years |
Limits — intake, not external dose
- Alpha reaches nothing through skin — Gd-148 is an intake problem, not an external one.
- What every sheet leaves out, internal dose included.
Decay and mass calculators for Gd-148
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.