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Radionuclide Dosimetric Data Sheets
Actinium-226
Summary data
General
Classification
Isotope: Ac-226
Atomic number (Z): 89
Mass number (A): 226
Neutron number (N): 137
Radioactive decay
Decay modes: α, β-, Electron capture
Half-life: 29.37 [h]
Decay constant: 6.5557e-06 [1/s]
Daughters: Th-226 (83.0%), Ra-226 (17.0%), Fr-222 (0.006%)
Radioactive daughters: Th-226, Ra-226, Fr-222
Dosimetric constants
Mean alpha energy: 0.0003 [MeV]
Mean electron energy: 0.29143 [MeV]
Mean photon energy: 0.13271 [MeV]
Air kerma rate constant, Γ10: 1.048e-17 [Gy·m2/Bq·s]
Air kerma coefficient, Kair: 1.048e-17 [Gy·m2/Bq·s]
Equilibrium dose constant for weakly-penetrating radiations (α and/or
electrons), Δwp: 4.674e-14 [Gy·kg/Bq·s]
Equilibrium dose constant for alphas, Δα: 4.807e-17
[Gy·kg/Bq·s]
Equilibrium dose constant for betas/electrons, Δβ-,β+,e-:
4.669e-14 [Gy·kg/Bq·s]
Equilibrium dose constant for photons, Δp: 2.126e-14
[Gy·kg/Bq·s]
Dose point kernels (plot)
Dose point kernel source: Graves, et al. Medical Physics. 2019 Nov.; 46(11):5284-5293.
Note: Bins are spaced every 0.1 mm until a radius of 10 cm, and every 1 mm until a radius of 2 m.
Download tabulated dose point kernel file here: www.mirdsoft.org/products/MIRDspecs/Ac-226 DPK.csv
Summary spectra (plot)
Spectra source: ICRP Publication 107: Nuclear Decay Data for Dosimetric Calculations. Ann. ICRP 2008, 38 (3).
Download tabulated summary spectra file here: www.mirdsoft.org/products/MIRDspecs/Ac-226 Summary Spectrum.csv
Beta spectra (plot)
Spectra source: ICRP Publication 107: Nuclear Decay Data for Dosimetric Calculations. Ann. ICRP 2008, 38 (3).
Download tabulated beta spectra file here: www.mirdsoft.org/products/MIRDspecs/Ac-226 Beta Spectrum.csv
Tabulated data
Summary spectra (table)
Spectra source: ICRP Publication 107: Nuclear Decay Data for Dosimetric Calculations. Ann. ICRP 2008, 38 (3).
Note: Radiations with yield < 0.01 are excluded from the table, but are available in the linked *.csv data.
Download tabulated summary spectra file here: www.mirdsoft.org/products/MIRDspecs/Ac-226 Summary Spectrum.csv
|
Energy [MeV] |
Yield [#/nt] if > 0.01 |
Radiation type |
|
7.12224e-05 |
2.791e+00 |
X-ray |
|
8.23158e-05 |
3.625e+00 |
X-ray |
|
2.88408e-03 |
1.427e-02 |
X-ray |
|
3.07056e-03 |
2.008e-02 |
X-ray |
|
1.23447e-02 |
3.417e-02 |
X-ray |
|
1.29764e-02 |
4.179e-02 |
X-ray |
|
1.53013e-02 |
2.528e-02 |
X-ray |
|
1.62776e-02 |
5.064e-02 |
X-ray |
|
1.90652e-02 |
1.126e-02 |
X-ray |
|
8.57602e-02 |
3.645e-02 |
X-ray |
|
8.88641e-02 |
5.953e-02 |
X-ray |
|
9.03299e-02 |
1.081e-02 |
X-ray |
|
9.37949e-02 |
1.748e-02 |
X-ray |
|
1.00546e-01 |
1.319e-02 |
X-ray |
|
1.58050e-01 |
1.748e-01 |
Gamma |
|
1.85600e-01 |
4.759e-02 |
Gamma |
|
2.30000e-01 |
2.689e-01 |
Gamma |
|
2.53500e-01 |
5.713e-02 |
Gamma |
|
2.81164e-01 |
4.890e-01 |
Beta |
|
3.39547e-01 |
9.980e-02 |
Beta |
|
3.66699e-01 |
2.395e-01 |
Beta |
|
2.56147e-05 |
7.680e-01 |
Auger electron |
|
5.13342e-05 |
8.728e-01 |
Auger electron |
|
1.20399e-04 |
7.757e-01 |
Auger electron |
|
1.33171e-04 |
9.658e-01 |
Auger electron |
|
1.81298e-04 |
4.379e-01 |
Auger electron |
|
1.88154e-04 |
5.534e-01 |
Auger electron |
|
4.66943e-04 |
1.120e-01 |
Auger electron |
|
4.99430e-04 |
1.420e-01 |
Auger electron |
|
1.39028e-03 |
3.461e-02 |
Auger electron |
|
1.71099e-03 |
2.626e-02 |
Auger electron |
|
2.21594e-03 |
2.469e-01 |
Auger electron |
|
2.32627e-03 |
3.145e-01 |
Auger electron |
|
2.58674e-03 |
3.967e-02 |
Auger electron |
|
2.74367e-03 |
5.420e-02 |
Auger electron |
|
9.32560e-03 |
6.646e-02 |
Auger electron |
|
9.95902e-03 |
8.353e-02 |
Auger electron |
|
1.22516e-02 |
3.219e-02 |
Auger electron |
|
1.30954e-02 |
4.166e-02 |
Auger electron |
|
4.79400e-02 |
2.288e-02 |
Conversion electron |
|
4.90400e-02 |
2.657e-02 |
Conversion electron |
|
5.21440e-02 |
2.205e-02 |
Conversion electron |
|
5.24500e-02 |
1.212e-01 |
Conversion electron |
|
5.59150e-02 |
9.577e-02 |
Conversion electron |
|
6.38263e-02 |
1.347e-02 |
Conversion electron |
|
6.81938e-02 |
6.102e-02 |
Conversion electron |
|
7.22300e-02 |
2.103e-02 |
Conversion electron |
|
1.19890e-01 |
1.467e-02 |
Conversion electron |
Useful Links
Isotope decay characteristics are periodically updated as better measurements can be made - changes that may not be reflected on this page. Please see useful links:
National Nuclear Data Center (NNDC): https://www.nndc.bnl.gov/nudat3/mird/
International Atomic Energy Agency (IAEA) Livechart: https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html
Reference Links
ICRP Report 107: https://www.icrp.org/publication.asp?id=ICRP%20Publication%20107
Graves et al. Dose Point Kernels: https://doi.org/10.1002/mp.13789
MIRD Decay Schemes 2nd Edition: https://sites.snmmi.org/SNMMI-MAIN/iCore/Store/StoreLayouts/Item_Detail.aspx?iProductCode=0-932004-80-6
MIRDsoft MIRDspecs version 20250101 (www.mirdsoft.org)
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