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Nuclide reference

Th-232 — Thorium-232

The half-life of Th-232 is 14.05 billion years. Main decay mode: α decay to Ra-228 (100%).

Identification

Element
Thorium (Th)
Atomic number Z
90
Mass number A
232
State
Radioactive

Key quantities

Half-life
14.05 billion years
Specific activity
4,058 Bq/g
Gamma constant Γ
—
A1 / A2 for transport (SSR-6, НП-053-16)
unlimited / unlimited
D-value (НП-067-24)
—

Decay modes

  • α decay → Ra-228 — 100 %
  • spontaneous fission — 1.4e-9 %

Main gamma lines

Energy, keVYield, %
15.2109 · X-ray line3.718
12.3298 · X-ray line3.088
63.810.263
140.880.021

Lines of the bare nuclide (ENDF/B-VIII.0), without daughter ingrowth.

Alpha and beta particles

RadiationEnergy, keVYield, %
α4,012.378.2
3,947.221.7
3,811.10.069

Related calculators

DecayActivity ↔ massDose rateA1/A2 and package type

Other isotopes of this element

Th-228
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.

Thorium-232 (Th-232) — reference data

What is in the card

This card gathers the key data of radionuclide Th-232 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 Th-232 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.