Americium-243
Am-243 · Americium, Z = 95, A = 243
A gigabecquerel of Am-243 is 135 mg of material, which follows from a specific activity of 7.39e+9 Bq/g (0.200 Ci/g). Americium-243 decays by alpha decay with a half-life of 7364 years; forty years leaves 99.62% of today's activity and ten thousand years leaves 39.01%.
Alpha emission is led by 5.275 MeV at 86.74%, one of 5 recorded lines. None of it reaches through skin, so the limit here is intake, not external dose.
Decay is the only handle: forty years leaves 99.62% of today's activity and ten thousand years leaves 39.01%, with ten half-lives at 73,638 years and a mean life of 10,624 years per atom.
Half-life 7364 years, 7.39e+9 Bq/g, and no line recorded
| Half-life | 7364 years (2.324e+11 s) |
| Decay mode | alpha decay |
| Specific activity | 7.39e+9 Bq/g (0.200 Ci/g) |
5 alpha lines, strongest 5.275 MeV
5 recorded lines from 5.181 to 5.349 MeV, the strongest 5.275 MeV at 86.74% of 100.0% total alpha emission.
| Energy (MeV) | Emission probability (%) |
|---|---|
| 5.2753 | 86.74 |
| 5.2333 | 11.46 |
| 5.1810 | 1.383 |
| 5.3494 | 0.24 |
| 5.3210 | 0.192 |
Activity over millennia
Ten half-lives is 73,638 years. On any timescale a facility can be planned over the activity is constant — 99.62% is left after forty years — and the mean life 1/λ is 10,624 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 | 24,462 years |
| Time to fall to 1 % | 48,924 years |
| Time to fall to 0.1 % | 73,386 years |
Limits — intake, not external dose
- Alpha reaches nothing through skin — Am-243 is an intake problem, not an external one.
- What every sheet leaves out, internal dose included.
Decay and mass calculators for Am-243
Other Americium nuclides: Am-241
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.