Plutonium-244
Pu-244 · Plutonium, Z = 94, A = 244
Plutonium-244 (Pu-244) is slow enough to be handled as a material rather than as a trace: 6.67e+5 Bq/g, or 0.0000180 Ci/g, puts a gigabecquerel at 1.50 kg. Decay is by alpha decay, half-life 8.13 × 10⁷ years, and shedding even one per cent of the activity takes 1.18 million years.
Alpha emission is led by 4.589 MeV at 80.5025%, 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: forty years leaves 100.00% of today's activity and ten thousand years leaves 99.99%, with ten half-lives at 813 million years and a mean life of 117 million years per atom.
Half-life 8.13 × 10⁷ years, 6.67e+5 Bq/g, and no line recorded
| Half-life | 8.13 × 10⁷ years (2.566e+15 s) |
| Decay mode | alpha decay |
| Specific activity | 6.67e+5 Bq/g (0.0000180 Ci/g) |
2 alpha lines, strongest 4.589 MeV
2 recorded lines from 4.546 to 4.589 MeV, the strongest 4.589 MeV at 80.5025% of 99.88% total alpha emission.
| Energy (MeV) | Emission probability (%) |
|---|---|
| 4.5890 | 80.5025 |
| 4.5460 | 19.3765 |
Activity over geological time
Ten half-lives is 813 million years. On any timescale a facility can be planned over the activity is constant — 100.00% is left after forty years — and the mean life 1/λ is 117 million 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 | 270 million years |
| Time to fall to 1 % | 540 million years |
| Time to fall to 0.1 % | 810 million years |
Limits — intake, not external dose
- Alpha reaches nothing through skin — Pu-244 is an intake problem, not an external one.
- What every sheet leaves out, internal dose included.
Decay and mass calculators for Pu-244
Other Plutonium nuclides: Pu-238, Pu-239, Pu-240, Pu-241, Pu-242
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.