Californium-252
Cf-252 · Californium, Z = 98, A = 252
Californium-252 decays by alpha decay, half-life 2.647 years. Specific activity is 1.98e+13 Bq/g (536 Ci/g), so a gigabecquerel comes to 50.4 µg — weighable, but on an analytical balance. Over a year the activity falls to 76.96%, and over forty years to 2.8e-3%.
Alpha emission is led by 6.118 MeV at 81.4996%, 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 76.96% of today's activity and forty years leaves 2.8e-3%, with ten half-lives at 26.5 years and a mean life of 3.82 years per atom.
Half-life 2.647 years, 1.98e+13 Bq/g, and no line recorded
| Half-life | 2.647 years (8.353e+7 s) |
| Decay mode | alpha decay |
| Specific activity | 1.98e+13 Bq/g (536 Ci/g) |
3 alpha lines, strongest 6.118 MeV
3 recorded lines from 5.977 to 6.118 MeV, the strongest 6.118 MeV at 81.4996% of 96.28% total alpha emission.
| Energy (MeV) | Emission probability (%) |
|---|---|
| 6.1181 | 81.4996 |
| 6.0756 | 14.5362 |
| 5.9766 | 0.2423 |
Activity over decades and centuries
Ten half-lives is 26.5 years, which puts decay storage out of reach: 2.8e-3% survives forty years. The mean life 1/λ, the quantity that enters an integrated dose, is 3.82 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 | 8.79 years |
| Time to fall to 1 % | 17.6 years |
| Time to fall to 0.1 % | 26.4 years |
Limits — intake, not external dose
- Alpha reaches nothing through skin — Cf-252 is an intake problem, not an external one.
- What every sheet leaves out, internal dose included.
Decay and mass calculators for Cf-252
Other Californium nuclides: Cf-249
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.