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Nuclide reference

Ra-222 — Radium-222

The half-life of Ra-222 is 36.17 s. Main decay mode: α decay to Rn-218 (100%).

Identification

Element
Radium (Ra)
Atomic number Z
88
Mass number A
222
State
Radioactive

Key quantities

Half-life
36.17 s
Specific activity
5.198e+19 Bq/g
Gamma constant Γ
—
D-value (НП-067-24)
—

Decay modes

Main gamma lines

Energy, keVYield, %
324.312.77
609.31 (Rn-218)0.1241
83.789 · X-ray line0.07582
81.071 · X-ray line0.04599
799.7 (Po-214)0.01036
328.90.004
472.590.0039
840.180.0028
515.830.00142
653.140.00024

Includes daughter nuclides in equilibrium: Rn-218, Po-214 (yield per decay of Ra-222); the emitting nuclide is in brackets. Equilibrium is reached in about 0.25 s. Equilibrium with radon requires a sealed source.

Alpha and beta particles

RadiationEnergy, keVYield, %
α6,55996.9
6,2413.05
7,129.2 (Rn-218)99.97
7,686.8 (Po-214)100.1

Related calculators

DecayActivity ↔ massDose rate

Other isotopes of this element

Ra-223Ra-226
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.

Radium-222 (Ra-222) — reference data

What is in the card

This card gathers the key data of radionuclide Ra-222 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 Ra-222 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.