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Radionuclide Dosimetric Data Sheets

Thorium-231

Summary data

General

Classification

Isotope:  Th-231
Atomic number (Z):  90
Mass number (A):  231
Neutron number (N):  141

Radioactive decay

Decay modes:  β-
Half-life:  25.52 [h]
Decay constant:  7.5447e-06 [1/s]
Daughters:  Pa-231 (100.0%)
Radioactive daughters:  Pa-231

Dosimetric constants

Mean alpha energy:  0.0 [MeV]
Mean electron energy:  0.1622 [MeV]
Mean photon energy:  0.02686 [MeV]
Air kerma rate constant, Γ10:  1.902e-17 [Gy·m2/Bq·s]
Air kerma coefficient, Kair:  1.902e-17 [Gy·m2/Bq·s]
Equilibrium dose constant for weakly-penetrating radiations (α and/or electrons), Δwp:  2.599e-14 [Gy·kg/Bq·s]
Equilibrium dose constant for alphas, Δα:  0.000e+00 [Gy·kg/Bq·s]
Equilibrium dose constant for betas/electrons, Δβ-,β+,e-:  2.599e-14 [Gy·kg/Bq·s]
Equilibrium dose constant for photons, Δp:  4.303e-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/Th-231 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/Th-231 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/Th-231 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/Th-231 Summary Spectrum.csv

 

Energy [MeV]

Yield [#/nt] if > 0.01

Radiation type

7.65093e-05

2.443e+01

X-ray

3.17063e-03

1.348e-01

X-ray

1.14081e-02

1.832e-02

X-ray

1.31269e-02

3.021e-02

X-ray

1.32994e-02

2.655e-01

X-ray

1.60398e-02

5.526e-02

X-ray

1.61112e-02

1.183e-02

X-ray

1.66446e-02

1.024e-02

X-ray

1.67859e-02

1.826e-01

X-ray

1.69536e-02

1.056e-02

X-ray

1.96582e-02

4.100e-02

X-ray

2.56400e-02

1.412e-01

Gamma

8.42140e-02

6.600e-02

Gamma

3.74941e-02

2.720e-02

Beta

5.55493e-02

1.243e-01

Beta

5.82484e-02

1.263e-02

Beta

7.95026e-02

1.166e-01

Beta

7.97617e-02

3.885e-01

Beta

8.49467e-02

3.205e-01

Beta

6.45480e-05

5.999e+00

Auger electron

1.56407e-04

4.024e-02

Auger electron

1.67740e-04

6.429e+00

Auger electron

1.95073e-04

3.653e+00

Auger electron

5.50761e-04

1.283e+00

Auger electron

1.27148e-03

2.877e-01

Auger electron

1.32700e-03

9.038e-02

Conversion electron

2.39392e-03

2.015e+00

Auger electron

2.84966e-03

3.664e-01

Auger electron

3.45897e-03

2.146e-02

Auger electron

4.52700e-03

8.752e-02

Conversion electron

5.23800e-03

1.625e-01

Conversion electron

8.89700e-03

2.149e-01

Conversion electron

9.89787e-03

4.337e-01

Auger electron

1.30406e-02

3.184e-01

Conversion electron

1.31169e-02

2.179e-01

Auger electron

1.39106e-02

7.949e-02

Conversion electron

1.63676e-02

2.580e-02

Auger electron

1.72000e-02

1.137e-01

Conversion electron

1.80700e-02

2.788e-02

Conversion electron

2.14806e-02

1.219e-01

Conversion electron

2.56400e-02

4.051e-02

Conversion electron

3.81680e-02

2.868e-01

Conversion electron

4.18270e-02

2.391e-01

Conversion electron

5.44106e-02

1.481e-01

Conversion electron

5.85700e-02

5.158e-02

Conversion electron

6.01150e-02

4.914e-02

Conversion electron

6.09740e-02

2.208e-02

Conversion electron

6.31010e-02

5.506e-02

Conversion electron

6.38120e-02

3.569e-02

Conversion electron

6.74710e-02

3.328e-02

Conversion electron

7.70686e-02

1.436e-02

Conversion electron

8.00546e-02

3.049e-02

Conversion electron

8.42140e-02

1.048e-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

 

 

 

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