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Radionuclide Dosimetric Data Sheets

Actinium-225

Summary data

General

Classification

Isotope:  Ac-225
Atomic number (Z):  89
Mass number (A):  225
Neutron number (N):  136

Radioactive decay

Decay modes:  α
Half-life:  10.0 [d]
Decay constant:  8.0225e-07 [1/s]
Daughters:  Fr-221 (100.0%)
Radioactive daughters:  Fr-221

Dosimetric constants

Mean alpha energy:  5.8919 [MeV]
Mean electron energy:  0.02476 [MeV]
Mean photon energy:  0.01708 [MeV]
Air kerma rate constant, Γ10:  6.777e-18 [Gy·m2/Bq·s]
Air kerma coefficient, Kair:  6.777e-18 [Gy·m2/Bq·s]
Equilibrium dose constant for weakly-penetrating radiations (α and/or electrons), Δwp:  9.480e-13 [Gy·kg/Bq·s]
Equilibrium dose constant for alphas, Δα:  9.440e-13 [Gy·kg/Bq·s]
Equilibrium dose constant for betas/electrons, Δβ-,β+,e-:  3.967e-15 [Gy·kg/Bq·s]
Equilibrium dose constant for photons, Δp:  2.737e-15 [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-225 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-225 Summary 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-225 Summary Spectrum.csv

 

Energy [MeV]

Yield [#/nt] if > 0.01

Radiation type

6.06221e-05

7.334e+00

X-ray

2.80803e-03

3.424e-02

X-ray

1.20348e-02

6.945e-02

X-ray

1.44681e-02

1.399e-02

X-ray

1.48321e-02

6.719e-02

X-ray

1.73734e-02

1.448e-02

X-ray

8.35492e-02

1.134e-02

X-ray

8.64861e-02

1.862e-02

X-ray

9.99100e-02

1.014e-02

Gamma

3.07386e-05

1.991e+00

Auger electron

1.18835e-04

2.090e+00

Auger electron

1.83343e-04

1.164e+00

Auger electron

4.89395e-04

3.484e-01

Auger electron

1.42574e-03

7.438e-02

Auger electron

2.18282e-03

6.216e-01

Auger electron

2.54383e-03

9.748e-02

Auger electron

6.89001e-03

1.946e-02

Conversion electron

6.95550e-03

6.894e-02

Conversion electron

8.02900e-03

3.548e-02

Conversion electron

9.25118e-03

1.542e-01

Auger electron

1.06000e-02

2.354e-02

Conversion electron

1.09660e-02

3.728e-02

Conversion electron

1.20897e-02

7.379e-02

Auger electron

1.86790e-02

7.180e-02

Conversion electron

2.05590e-02

4.235e-02

Conversion electron

2.16160e-02

7.091e-02

Conversion electron

2.23555e-02

1.970e-02

Conversion electron

2.34960e-02

4.138e-02

Conversion electron

3.30055e-02

3.888e-02

Conversion electron

3.48855e-02

2.283e-02

Conversion electron

3.66500e-02

1.288e-02

Conversion electron

4.43200e-02

3.528e-02

Conversion electron

5.57400e-02

1.179e-02

Conversion electron

8.10000e-02

1.246e-02

Conversion electron

5.58072e+00

1.202e-02

Alpha

5.60906e+00

1.102e-02

Alpha

5.63741e+00

4.408e-02

Alpha

5.68234e+00

1.302e-02

Alpha

5.72325e+00

3.106e-02

Alpha

5.73162e+00

1.322e-02

Alpha

5.73189e+00

8.015e-02

Alpha

5.79187e+00

8.616e-02

Alpha

5.79372e+00

1.813e-01

Alpha

5.82972e+00

5.079e-01

Alpha

1.01074e-01

1.202e-02

Alpha recoil

1.01587e-01

1.102e-02

Alpha recoil

1.02101e-01

4.408e-02

Alpha recoil

1.02915e-01

1.302e-02

Alpha recoil

1.03656e-01

3.106e-02

Alpha recoil

1.03807e-01

1.322e-02

Alpha recoil

1.03812e-01

8.015e-02

Alpha recoil

1.04898e-01

8.616e-02

Alpha recoil

1.04932e-01

1.813e-01

Alpha recoil

1.05584e-01

5.079e-01

Alpha recoil

 

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

 

 

 

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