Tantalum-182m1
Ta-182m1 · Tantalum, Z = 73, A = 182 · isomeric state m1
Tantalum-182m1 (Ta-182m1) carries 8.11e+21 Bq/g, or 2.19e+11 Ci/g: a gigabecquerel is 123 fg, no weighable quantity at all. It decays by isomeric transition with a half-life of 283 milliseconds, which leaves 0% of today's activity after a day and 0% after a week.
All 2 recorded photon lines sit below the 20 keV cutoff, so Γ is zero by convention and no external dose rate is quoted. The strongest line is 16.27 keV. A monitor calibrated on Cs-137 under-responds at these energies, so a reading taken without an energy correction understates Ta-182m1 rather than missing it outright. The recorded spectrum runs 9.42 to 16.3 keV and carries 20.3% emission probability in all, which sets what a thin-window or proportional detector has to see.
Decay is the only handle: a day leaves 0% of today's activity and a week leaves 0%, with ten half-lives at 2.83 seconds and a mean life of 0.408 seconds per atom.
Half-life 283 milliseconds, 8.11e+21 Bq/g, and no line recorded
| Half-life | 283 milliseconds (0.2830 s) |
| Decay mode | isomeric transition |
| Specific activity | 8.11e+21 Bq/g (2.19e+11 Ci/g) |
Activity over the first hours
Ten half-lives is 2.83 seconds, so the activity moves measurably while a count is running: every figure has to carry the time it was referred to. The mean life 1/λ is 0.408 seconds.
| 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 | 0.940 seconds |
| Time to fall to 1 % | 1.88 seconds |
| Time to fall to 0.1 % | 2.82 seconds |
Limits of these figures
- Γ excludes 2 lines under 20 keV, carrying 20.3% of all emissions.
- What every sheet leaves out, internal dose included.
Decay and mass calculators for Ta-182m1
Other Tantalum nuclides: Ta-182, Ta-182m2
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.