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Radionuclide Dosimetric Data Sheets
Radium-221
Summary data
General
Classification
Isotope: Ra-221
Atomic number (Z): 88
Mass number (A): 221
Neutron number (N): 133
Radioactive decay
Decay modes: α
Half-life: 28.0 [s]
Decay constant: 2.4755e-02 [1/s]
Daughters: Rn-217 (100.0%)
Radioactive daughters: Rn-217
Dosimetric constants
Mean alpha energy: 6.7915 [MeV]
Mean electron energy: 0.06897 [MeV]
Mean photon energy: 0.03901 [MeV]
Air kerma rate constant, Γ10: 8.997e-18 [Gy·m2/Bq·s]
Air kerma coefficient, Kair: 8.997e-18 [Gy·m2/Bq·s]
Equilibrium dose constant for weakly-penetrating radiations (α and/or
electrons), Δwp: 1.099e-12 [Gy·kg/Bq·s]
Equilibrium dose constant for alphas, Δα: 1.088e-12
[Gy·kg/Bq·s]
Equilibrium dose constant for betas/electrons, Δβ-,β+,e-:
1.105e-14 [Gy·kg/Bq·s]
Equilibrium dose constant for photons, Δp: 6.250e-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/Ra-221 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/Ra-221 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/Ra-221 Summary Spectrum.csv
|
Energy [MeV] |
Yield [#/nt] if > 0.01 |
Radiation type |
|
5.00882e-05 |
8.950e+00 |
X-ray |
|
2.71194e-03 |
4.131e-02 |
X-ray |
|
1.17297e-02 |
8.655e-02 |
X-ray |
|
1.38944e-02 |
1.238e-02 |
X-ray |
|
1.40892e-02 |
1.728e-02 |
X-ray |
|
1.43744e-02 |
5.184e-02 |
X-ray |
|
1.45241e-02 |
1.245e-02 |
X-ray |
|
1.68365e-02 |
1.106e-02 |
X-ray |
|
8.13681e-02 |
2.509e-02 |
X-ray |
|
8.41450e-02 |
4.137e-02 |
X-ray |
|
9.30200e-02 |
3.000e-02 |
Gamma |
|
1.49200e-01 |
1.250e-01 |
Gamma |
|
1.74300e-01 |
2.125e-02 |
Gamma |
|
3.68165e-05 |
2.315e+00 |
Auger electron |
|
1.14093e-04 |
2.637e+00 |
Auger electron |
|
1.80675e-04 |
1.444e+00 |
Auger electron |
|
4.76077e-04 |
3.715e-01 |
Auger electron |
|
1.10838e-03 |
2.434e-01 |
Auger electron |
|
2.12005e-03 |
7.890e-01 |
Auger electron |
|
2.45111e-03 |
1.177e-01 |
Auger electron |
|
9.03699e-03 |
1.972e-01 |
Auger electron |
|
1.17899e-02 |
9.301e-02 |
Auger electron |
|
1.45851e-02 |
1.044e-02 |
Auger electron |
|
3.81180e-02 |
3.130e-02 |
Conversion electron |
|
5.04360e-02 |
3.541e-02 |
Conversion electron |
|
7.08580e-02 |
2.453e-02 |
Conversion electron |
|
7.49780e-02 |
2.357e-01 |
Conversion electron |
|
7.55360e-02 |
4.975e-02 |
Conversion electron |
|
7.56240e-02 |
2.407e-02 |
Conversion electron |
|
8.95021e-02 |
6.241e-02 |
Conversion electron |
|
9.30200e-02 |
2.111e-02 |
Conversion electron |
|
1.31804e-01 |
7.001e-02 |
Conversion electron |
|
1.34581e-01 |
4.465e-02 |
Conversion electron |
|
1.45682e-01 |
3.282e-02 |
Conversion electron |
|
1.49200e-01 |
1.077e-02 |
Conversion electron |
|
6.58818e+00 |
5.531e-02 |
Alpha |
|
6.61285e+00 |
3.753e-01 |
Alpha |
|
6.66799e+00 |
2.272e-01 |
Alpha |
|
6.67203e+00 |
1.481e-02 |
Alpha |
|
6.75932e+00 |
3.160e-01 |
Alpha |
|
1.21520e-01 |
5.531e-02 |
Alpha recoil |
|
1.21975e-01 |
3.753e-01 |
Alpha recoil |
|
1.22992e-01 |
2.272e-01 |
Alpha recoil |
|
1.23067e-01 |
1.481e-02 |
Alpha recoil |
|
1.24677e-01 |
3.160e-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
MIRDsoft MIRDspecs version 20250101 (www.mirdsoft.org)
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