Plutonium-240
| General | |
|---|---|
| Symbol | 240Pu |
| Names | plutonium-240 |
| Protons (Z) | 94 |
| Neutrons (N) | 146 |
| Nuclide data | |
| Natural abundance | Trace |
| Half-life (t1/2) | 6561(7) years |
| Isotope mass | 240.053812 Da |
| Decay products | 236U |
| Decay modes | |
| Decay mode | Decay energy (MeV) |
| Alpha decay | 5.256 |
| Isotopes of plutonium Complete table of nuclides | |
Plutonium-240 (240
Pu or Pu-240) is an isotope of plutonium formed when plutonium-239 captures a neutron without undergoing fission. The detection of its spontaneous fission led to its discovery in 1944 at Los Alamos and had important consequences for the Manhattan Project.
As with the other major plutonium isotopes, the normal decay leads to a more-stable isotope of uranium (236U) and in effect no further decay chain on human timescales. Over geologic time it would follow the thorium series.
240Pu undergoes spontaneous fission as a secondary decay mode at a small but significant rate. The presence of 240Pu limits plutonium's use in a nuclear bomb, because the neutron flux from spontaneous fission initiates the chain reaction prematurely, causing an early release of energy that physically disperses the core before full implosion is reached (a "fizzle").