Pu-240

Pu-240 is isotope of Plutonium, element number 94.

Isotope mass: 240.0538135 Dalton

Half-life: 6561 y

Energy at the spontaneous alpha-decay: 5.25575 MeV

Production

Pu-240, as other isotopes of plutionium, appear as by-products at the nuclear chain reaction in the most of commercial nuclear plants; usually, the nuclear fuel has a lot of U-238. Then,

\( \displaystyle \rm {}^{238}_{92}U + {}^{1}_{0}n ~ \longrightarrow ~ {}^{239}_{92}U \xrightarrow [23.5 \ min]{\beta^-} {}^{239}_{93}Np \xrightarrow [2.356\ d]{\beta^-} {}^{239}_{94}Pu \)

\( \displaystyle \rm {}^{239}_{94}Pu + {}^{1}_{0}n ~ \longrightarrow ~ {}^{240}_{94}Pu \) + dropping of extra energy with gamma-rays.

The isotopes of Plutonium (perhaps, except Pu-239) are considered as unwanted products.
Up to year 2022, no commercially-efficient tools for the separation are available; so, they appear as contaminants, as dangerous (and long-living) components of the nuclear waste.

Spontaneous decay chain

\(\rm ^{240}_{94}Pu \xrightarrow [6561\ y]{\alpha,\ 5.25575\ MeV} {}^{236}_{92}U \xrightarrow [2.348e7\ y]{\alpha,\ 4.572\ MeV} {}^{232}_{88}Th \ .. \)

U-236 is much more stable, than Pu-240. At consideration of the relaxation heat, in the first approach, the only fist decay in the chain above needs to be taken into account.

Warning

The most of data are taken from Wikipedia.

So, some additional misprints from Wikipedia may appear here in addition to those made by the Editor of TORI.

References

https://en.wikipedia.org/wiki/Plutonium-240 Plutonium-240 (²⁴⁰Pu or Pu-240) is an isotope of plutonium formed when plutonium-239 captures a neutron. The detection of its spontaneous fission led to its discovery in 1944 at Los Alamos and had important consequences for the Manhattan Project.[3] 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.[4][5] It decays by alpha emission to uranium-236.

Keywords

«Nuclear waste», «Pu-239», «Pu-240», «Pu-241», «Pu-242», «Relaxation heat», «U-236»