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Nuclide reference

Fr-221 — Francium-221

The half-life of Fr-221 is 4.9 min. Main decay mode: α decay to At-217 (100%).

Identification

Element
Francium (Fr)
Atomic number Z
87
Mass number A
221
State
Radioactive

Key quantities

Half-life
4.9 min
Specific activity
6.424e+18 Bq/g
Gamma constant Γ
—
D-value (НП-067-24)
—

Decay modes

Main gamma lines

Energy, keVYield, %
218.1211.38
81.517 · X-ray line1.357
78.948 · X-ray line0.8193
410.640.1201
100.250.1018
171.830.07736
150.210.04784
359.860.04072
382.340.03359
257.9 (At-217)0.0287

Includes daughter nuclides in equilibrium: At-217 (yield per decay of Fr-221); the emitting nuclide is in brackets. Equilibrium is reached in about 0.23 s.

Alpha and beta particles

RadiationEnergy, keVYield, %
α6,34183.4
6,126.315.1
6,2431.34
7,066.9 (At-217)99.9

Related calculators

DecayActivity ↔ massDose rate
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.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.

Francium-221 (Fr-221) — reference data

What is in the card

This card gathers the key data of radionuclide Fr-221 in one place: half-life, decay modes, main gamma lines, alpha and beta particle energies, gamma constant, specific activity and the D-value for source categorization. Decay and emission data are from ENDF/B-VIII.0; the D-value follows NP-067-24; the gamma constant is the ambient dose equivalent H*(10) at 1 m, computed from ICRP-107 spectra.

How to use the data

Half-life and specific activity let you recalculate the activity of a Fr-221 source to the delivery or disposal date — use the decay calculator. Gamma lines with yields identify the nuclide from a spectrum and pick the line for gamma spectrometry; the gamma constant Γ gives the dose rate at a distance, while the D-value and A1/A2 set the source category and the package type for transport.