Yttrium-88m2
Y-88m2 · Yttrium, Z = 39, A = 88 · isomeric state m2
Yttrium-88m2 (Y-88m2) carries 3.40e+23 Bq/g, or 9.18e+12 Ci/g: a gigabecquerel is 2.94 fg, no weighable quantity at all. It decays by isomeric transition with a half-life of 13.98 milliseconds, which leaves 0% of today's activity after a day and 0% after a week.
1 GBq at 1 m reads 0.0876 mGy/h, and 1 Ci at the same distance 3.24 mGy/h, from an air kerma rate constant of 0.0876 mGy·m²/(GBq·h) — 1.1× Cs-137 and 3.5× less than Co-60, and 24 of 96 among the photon emitters carried here.
2 lines clear the 20 keV cutoff, but 2 of them carry 90% of the dose rate. The leading one is 442.6 keV at 67.3% of the total — its emission probability is 98.22%, which is also the highest.
Halving the air kerma rate calls for 1.96 mm of lead, or 8.64 mm of steel where lead is unwelcome, and a factor of ten calls for 8.55 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 4.96 mm of lead. The tenth-value layer runs 4.3 times the half-value layer, not the 3.32 a single energy would give.
Half-life, specific activity and dose rate
| Half-life | 13.98 milliseconds (0.01398 s) |
| Decay mode | isomeric transition |
| Specific activity | 3.40e+23 Bq/g (9.18e+12 Ci/g) |
| Air kerma rate constant Γ (δ = 20 keV) | 0.0876 mGy·m²/(GBq·h) |
| Dose rate, 1 GBq at 1 m | 0.0876 mGy/h |
| Dose rate, 1 Ci at 1 m | 3.24 mGy/h |
| Kerma-weighted mean photon energy | 373.8 keV |
443 keV leads, and 2 lines make 90%
6 further lines below the 20 keV cutoff, the highest at 17.01 keV and 2.73% emission probability in all, are excluded here and from Γ. Why the two columns rank differently.
| Energy (keV) | Emission probability (%) | Share of dose rate (%) |
|---|---|---|
| 442.62 | 98.22 | 67.32 |
| 231.93 | 98.09 | 32.68 |
1.96 mm of lead halves this spectrum
Solved numerically across all 2 lines, narrow beam. Why not one representative energy.
| Material | HVL (mm) | TVL (mm) | TVL / HVL |
|---|---|---|---|
| lead | 1.96 | 8.55 | 4.35 |
| tungsten | 1.40 | 5.99 | 4.26 |
| iron | 8.64 | 29.5 | 3.41 |
| copper | 7.47 | 25.7 | 3.44 |
| concrete | 29.5 | 99.1 | 3.36 |
| water | 62.7 | 211 | 3.36 |
| aluminum | 26.5 | 89.0 | 3.36 |
A single energy would give 3.32. What a spread of energies does instead.
Activity over the first hours
Ten half-lives is 0.140 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 0.0202 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 | 0.0464 seconds |
| Time to fall to 1 % | 0.0929 seconds |
| Time to fall to 0.1 % | 0.139 seconds |
Limits of these dose rates
- 0.0876 mGy/h at a metre — bare point source, no capsule, no self-absorption.
- 1.96 mm of lead halves this spectrum, narrow beam, scatter not added back.
- Γ excludes 6 lines under 20 keV, carrying 2.73% of all emissions.
- What every sheet leaves out, internal dose included.
Gamma and decay calculators for Y-88m2
Other Yttrium nuclides: Y-88, Y-88m1, 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.