Nuclide reference
Tl-201 — Thallium-201
The half-life of Tl-201 is 3.0421 d. Main decay mode: electron capture to Hg-201 (100%).
Identification
- Element
- Thallium (Tl)
- Atomic number Z
- 81
- Mass number A
- 201
- State
- Radioactive
Key quantities
- Half-life
- 3.0421 d
- Specific activity
- 7.901e+15 Bq/g
- Gamma constant Γ (H*(10))
- 0.01756 µSv·m²/(MBq·h)
- Dose rate, 1 GBq at 1 m
- ≈ 17.6 µSv/h
- A1 / A2 for transport (SSR-6, НП-053-16)
- 10 TBq / 4 TBq
- D-value (НП-067-24)
- 1 TBq
Decay modes
- electron capture → Hg-201 — 100 %
Main gamma lines
| Energy, keV | Yield, % |
|---|---|
| 70.819 · X-ray line | 46.36 |
| 68.894 · X-ray line | 27.22 |
| 167.43 | 10 |
| 135.34 | 2.565 |
| 141.1 | 0.28 |
| 32.19 | 0.258 |
| 30.6 | 0.253 |
| 165.88 | 0.155 |
| 26.34 | 0.008 |
Lines of the bare nuclide (ENDF/B-VIII.0), without daughter ingrowth.
Related calculators
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.