Uranium-232
U-232 · Uranium, Z = 92, A = 232
A gigabecquerel of U-232 is 1.21 mg of material, which follows from a specific activity of 8.27e+11 Bq/g (22.4 Ci/g). Uranium-232 decays by alpha decay with a half-life of 68.9 years; a year leaves 99.00% of today's activity and forty years leaves 66.87%.
Alpha emission is led by 5.320 MeV at 68.15%, one of 3 recorded lines. None of it reaches through skin, so the limit here is intake, not external dose.
Decay is the only handle: a year leaves 99.00% of today's activity and forty years leaves 66.87%, with ten half-lives at 689 years and a mean life of 99.4 years per atom.
Half-life 68.9 years, 8.27e+11 Bq/g, and no line recorded
| Half-life | 68.9 years (2.174e+9 s) |
| Decay mode | alpha decay |
| Specific activity | 8.27e+11 Bq/g (22.4 Ci/g) |
3 alpha lines, strongest 5.320 MeV
3 recorded lines from 5.139 to 5.320 MeV, the strongest 5.320 MeV at 68.15% of 100.0% total alpha emission.
| Energy (MeV) | Emission probability (%) |
|---|---|
| 5.3201 | 68.15 |
| 5.2634 | 31.55 |
| 5.1390 | 0.3 |
Activity over decades and centuries
Ten half-lives is 689 years, which puts decay storage out of reach: 66.87% survives forty years. The mean life 1/λ, the quantity that enters an integrated dose, is 99.4 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 | 229 years |
| Time to fall to 1 % | 458 years |
| Time to fall to 0.1 % | 687 years |
Limits — intake, not external dose
- Alpha reaches nothing through skin — U-232 is an intake problem, not an external one.
- What every sheet leaves out, internal dose included.
Decay and mass calculators for U-232
Other Uranium nuclides: U-233, U-234, U-235, U-236, U-238, U-238m
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.