Nuclide reference
U-240 — Uranium-240
The half-life of U-240 is 14.1 h. Main decay mode: β⁻ decay to Np-240m (100%).
Identification
- Element
- Uranium (U)
- Atomic number Z
- 92
- Mass number A
- 240
- State
- Radioactive
Key quantities
- Half-life
- 14.1 h
- Specific activity
- 3.426e+16 Bq/g
- Gamma constant Γ
- —
- D-value (НП-067-24)
- —
Decay modes
- β⁻ decay → Np-240m — 100 %
Main gamma lines
| Energy, keV | Yield, % |
|---|---|
| 554.6 (Np-240m) | 21.05 |
| 18.1431 (Np-240m) · X-ray line | 13.42 |
| 14.2742 (Np-240m) · X-ray line | 12.04 |
| 597.4 (Np-240m) | 11.79 |
| 1,496.9 (Np-240m) | 1.34 |
| 817.89 (Np-240m) | 1.289 |
| 938.02 (Np-240m) | 1.219 |
| 758.61 (Np-240m) | 1.189 |
| 263.37 (Np-240m) | 1.148 |
| 44.1 | 1.05 |
Includes daughter nuclides in equilibrium: Np-240m (yield per decay of U-240); the emitting nuclide is in brackets. Equilibrium is reached in about 7.8 h. In transient equilibrium a daughter's activity exceeds the parent's, so a yield can be above 100%.
Alpha and beta particles
| Radiation | Energy, keV | Yield, % |
|---|---|---|
| β⁻, E max | 380 | 75 |
| 335.83 | 25 | |
| 2,165.2 (Np-240m) | 42.31 | |
| 1,610.6 (Np-240m) | 31.23 |
For β⁻ the endpoint (maximum) energy of the spectrum is given. ENDF/B-VIII.0.
Related calculators
Other isotopes of this element
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.