Yttrium-88m1
Y-88m1 · Yttrium, Z = 39, A = 88 · isomeric state m1
Yttrium-88m1 (Y-88m1) carries 1.58e+25 Bq/g, or 4.26e+14 Ci/g: a gigabecquerel is 63.4 ag, no weighable quantity at all. It decays by isomeric transition with a half-life of 0.301 milliseconds, which leaves 0% of today's activity after a day and 0% after a week.
1 GBq at 1 m reads 0.0516 mGy/h, and 1 Ci at the same distance 1.91 mGy/h, from an air kerma rate constant of 0.0516 mGy·m²/(GBq·h) — 1.5× less than Cs-137 and 5.9× less than Co-60, and 41 of 96 among the photon emitters carried here.
One line at 392.9 keV carries all of that.
Halving the air kerma rate calls for 2.54 mm of lead, or 9.27 mm of steel where lead is unwelcome, and a factor of ten calls for 8.44 mm of lead — sheet thicknesses that a glovebox or a transport container can carry. Reaching 20 µSv/h from 1 GBq at a metre takes 3.47 mm of lead.
Half-life, specific activity and dose rate
| Half-life | 0.301 milliseconds (0.0003010 s) |
| Decay mode | isomeric transition |
| Specific activity | 1.58e+25 Bq/g (4.26e+14 Ci/g) |
| Air kerma rate constant Γ (δ = 20 keV) | 0.0516 mGy·m²/(GBq·h) |
| Dose rate, 1 GBq at 1 m | 0.0516 mGy/h |
| Dose rate, 1 Ci at 1 m | 1.91 mGy/h |
| Kerma-weighted mean photon energy | 392.9 keV |
A single photon line at 393 keV
6 further lines below the 20 keV cutoff, the highest at 17.01 keV and 2.01% emission probability in all, are excluded here and from Γ. Why the two columns rank differently.
| Energy (keV) | Emission probability (%) | Share of dose rate (%) |
|---|---|---|
| 392.87 | 97.21 | 100.00 |
2.54 mm of lead halves this spectrum
Solved numerically across all 1 line, narrow beam. Why not one representative energy.
| Material | HVL (mm) | TVL (mm) | TVL / HVL |
|---|---|---|---|
| lead | 2.54 | 8.44 | 3.32 |
| tungsten | 1.81 | 6.00 | 3.32 |
| iron | 9.27 | 30.8 | 3.32 |
| copper | 8.13 | 27.0 | 3.32 |
| concrete | 30.6 | 102 | 3.32 |
| water | 64.9 | 216 | 3.32 |
| aluminum | 27.5 | 91.3 | 3.32 |
A single energy would give 3.32. What a spread of energies does instead.
Activity over the first hours
Ten half-lives is 0.00301 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 0.000434 seconds.
| Elapsed | Fraction remaining |
|---|---|
| 1 half-life | 50.0 % |
| 2 half-lives | 25.0 % |
| 5 half-lives | 3.12 % |
| 10 half-lives | 0.0977 % |
| Time to fall to 10 % of today's activity | 0.00100 seconds |
| Time to fall to 1 % | 0.00200 seconds |
| Time to fall to 0.1 % | 0.00300 seconds |
Limits of these dose rates
- 0.0516 mGy/h at a metre — bare point source, no capsule, no self-absorption.
- 2.54 mm of lead halves this spectrum, narrow beam, scatter not added back.
- Γ excludes 6 lines under 20 keV, carrying 2.01% of all emissions.
- What every sheet leaves out, internal dose included.
Gamma and decay calculators for Y-88m1
Other Yttrium nuclides: Y-88, Y-88m2, Y-90, Y-90m, Y-91
Computed from the IAEA Nuclear Data Section — Livechart API (ENSDF) and the NIST X-Ray Mass Attenuation Coefficients. Derivations and citations.