Curium-242
Cm-242 · Curium, Z = 96, A = 242
At 1.23e+14 Bq/g — 3.31e+3 Ci/g — a gigabecquerel of Cm-242 amounts to 8.16 µg, which is why activity rather than mass is how anyone states the quantity. Curium-242 decays by alpha decay with a half-life of 162.88 days, falling to 88.01% of today's activity in a month and 21.13% in a year.
Alpha emission is led by 6.113 MeV at 74.08%, 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 month leaves 88.01% of today's activity and a year leaves 21.13%, with ten half-lives at 4.46 years and a mean life of 235 days per atom.
Half-life 162.88 days, 1.23e+14 Bq/g, and no line recorded
| Half-life | 162.88 days (1.407e+7 s) |
| Decay mode | alpha decay |
| Specific activity | 1.23e+14 Bq/g (3.31e+3 Ci/g) |
3 alpha lines, strongest 6.113 MeV
3 recorded lines from 5.969 to 6.113 MeV, the strongest 6.113 MeV at 74.08% of 100.0% total alpha emission.
| Energy (MeV) | Emission probability (%) |
|---|---|
| 6.1127 | 74.08 |
| 6.0694 | 25.92 |
| 5.9692 | 0.035 |
Activity over months and years
Ten half-lives is 4.46 years — a storage problem rather than a disposal one, with 21.13% of today's activity still there after a year. The mean life 1/λ is 235 days.
| 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 | 1.48 years |
| Time to fall to 1 % | 2.96 years |
| Time to fall to 0.1 % | 4.44 years |
Limits — intake, not external dose
- Alpha reaches nothing through skin — Cm-242 is an intake problem, not an external one.
- What every sheet leaves out, internal dose included.
Decay and mass calculators for Cm-242
Other Curium nuclides: Cm-243, Cm-244, Cm-245, Cm-246
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.