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Nuclide reference

Np-238 — Neptunium-238

The half-life of Np-238 is 2.117 d. Main decay mode: β⁻ decay to Pu-238 (100%).

Identification

Element
Neptunium (Np)
Atomic number Z
93
Mass number A
238
State
Radioactive

Key quantities

Half-life
2.117 d
Specific activity
9.589e+15 Bq/g
Gamma constant Γ
—
D-value (НП-067-24)
—

Decay modes

  • β⁻ decay → Pu-238 — 100 %

Main gamma lines

Energy, keVYield, %
984.4525.19
1,028.5418.29
18.1431 · X-ray line16.22
14.2744 · X-ray line14.51
1,025.878.716
923.982.62
882.630.8111
962.770.6449
918.690.5315
941.380.5139

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

Alpha and beta particles

RadiationEnergy, keVYield, %
β⁻, E max263.4644.8
1,247.941
222.0611.47
329.231.255

For β⁻ the endpoint (maximum) energy of the spectrum is given. ENDF/B-VIII.0.

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.

Neptunium-238 (Np-238) — reference data

What is in the card

This card gathers the key data of radionuclide Np-238 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 Np-238 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.