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Nuclide reference

Tc-99m — Technetium-99m

The half-life of Tc-99m is 6.0067 h. Main decay mode: isomeric transition to Tc-99 (100%).

Identification

Element
Technetium (Tc)
Atomic number Z
43
Mass number A
99
State
Radioactive

Key quantities

Half-life
6.0067 h
Specific activity
1.95e+17 Bq/g
Gamma constant Γ (H*(10))
0.02187 µSv·m²/(MBq·h)
Dose rate, 1 GBq at 1 m
≈ 21.9 µSv/h
A1 / A2 for transport (SSR-6, НП-053-16)
10 TBq / 4 TBq
D-value (НП-067-24)
0.7 TBq

Decay modes

  • isomeric transition → Tc-99 — 100 %
  • β⁻ decay → Ru-99 — 0.0037 %

Main gamma lines

Energy, keVYield, %
140.51189
18.368 · X-ray line4.063
18.251 · X-ray line2.137
142.630.02225
89.60.00104

Lines of the bare nuclide (ENDF/B-VIII.0), without daughter ingrowth.

Related calculators

DecayActivity ↔ massSource categoryDose rateA1/A2 and package type

Other isotopes of this element

Tc-99
Reference data vs computed valuesHalf-life, gamma lines and D-value are reference data (ENDF/B-VIII.0, НП-067-24).Gamma constant Γ is H*(10) at 1 m computed from ICRP-107 spectra (NIST µ_en/ρ, ICRP-74 Table A.21) including short-lived progeny in equilibrium (e.g. Cs-137/Ba-137m, Ra-226 series); specific activity uses molar mass M ≈ mass number A.Dose rate example: point source, no shielding or scatter, Ḣ = Γ·A/r².K-series X-ray energies are from NIST SRD 128 (Deslattes et al., 2003): in ENDF/B-VIII.0 they are given to 1 % and shifted by up to 0.7 keV for heavy elements. L-series lines and all yields are ENDF/B-VIII.0.

Technetium-99m (Tc-99m) — reference data

What is in the card

This card gathers the key data of radionuclide Tc-99m in one place: half-life, decay modes, main gamma lines, alpha and beta particle energies, gamma constant, specific activity and the D-value for source categorization. Decay and emission data are from ENDF/B-VIII.0; the D-value follows NP-067-24; the gamma constant is the ambient dose equivalent H*(10) at 1 m, computed from ICRP-107 spectra.

How to use the data

Half-life and specific activity let you recalculate the activity of a Tc-99m source to the delivery or disposal date — use the decay calculator. Gamma lines with yields identify the nuclide from a spectrum and pick the line for gamma spectrometry; the gamma constant Γ gives the dose rate at a distance, while the D-value and A1/A2 set the source category and the package type for transport.