Praseodymium-144
Pr-144 · Praseodymium, Z = 59, A = 144
Praseodymium-144 (Pr-144) carries 2.80e+18 Bq/g, or 7.56e+7 Ci/g: a gigabecquerel is 357 pg, no weighable quantity at all. It decays by beta-minus decay with a half-life of 17.28 minutes, which leaves 8.2e-24% of today's activity after a day and 2.5e-174% after a week.
The beta endpoint is 3.00 MeV, mean 1.21 MeV over 5 branches. That endpoint stops in 12.6 mm of acrylic or 5.93 mm of glass. Of the beta energy, 0.63% turns into X-rays in acrylic and 8.60% in lead.
Decay is the only handle: a day leaves 8.2e-24% of today's activity and a week leaves 2.5e-174%, with ten half-lives at 2.88 hours and a mean life of 24.9 minutes per atom.
Half-life, specific activity and beta endpoint
| Half-life | 17.28 minutes (1037 s) |
| Decay mode | beta-minus decay |
| Specific activity | 2.80e+18 Bq/g (7.56e+7 Ci/g) |
| Beta endpoint / mean | 3.00 MeV / 1.21 MeV |
12.6 mm of acrylic stops the 3.00 MeV endpoint
Katz–Penfold fit to the 3.00 MeV endpoint — ±10%, and a stopping thickness rather than an attenuation length. Why the material matters more than the thickness.
| Absorber | Range for the endpoint (mm) |
|---|---|
| acrylic | 12.6 |
| aluminum | 5.49 |
| water | 14.8 |
| glass | 5.93 |
| Shield material | Fraction of beta energy converted to X-rays |
|---|---|
| acrylic (Z ≈ 6) | 0.63% |
| lead (Z = 82) | 8.60% |
Activity over the first hours
Ten half-lives is 2.88 hours, 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 24.9 minutes.
| 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 | 57.4 minutes |
| Time to fall to 1 % | 1.91 hours |
| Time to fall to 0.1 % | 2.87 hours |
Limits of these range figures
- 12.6 mm of acrylic for the 3.00 MeV endpoint: a ±10% fit, and not a skin dose.
- What every sheet leaves out, internal dose included.
Beta and decay calculators for Pr-144
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.