- Plutonium-240
Infobox isotope
alternate_names =
symbol =Pu
mass_number =240
mass =
num_neutrons =146
num_protons =94
abundance = 0 (Artificial)
halflife = 6563 years
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decay_mode2 =
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parent =
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error2 =Plutonium-240 (Pu-240) is an
isotope of themetal plutonium formed whenplutonium-239 captures aneutron . About 62% to 73% of the time when Pu-239 captures a neutron it undergoes fission; the rest of the time it forms Pu-240. The longer anuclear fuel element remains in anuclear reactor the greater the relative percentage of Pu-240 in the fuel becomes. For weapons use, the fuel needs to be as low in Pu-240 as possible, usually around 7% of the total plutonium, but this is achieved by reprocessing the fuel after just 90 days of use. Such rapid fuel cycles are highly impractical for civilian power reactors and are normally only carried out with dedicated weapons plutonium production reactors. Spent civilian power reactor fuel typically has under 70% Pu-239 and around 26% Pu-240, the rest being made up of other plutonium isotopes, making it extremely difficult but not impossible to use it for manufacturingnuclear weapon s.240Pu has only about 1/3 as large a neutron absorption
cross section as 239Pu, and nearly always becomesplutonium-241 rather than fissioning. In general, isotopes of oddmass number are both more likely to absorb a neutron, and more likely to fission on neutron absorption, than isotopes of even mass number. Thus, even mass isotopes tend to accumulate, especially in athermal reactor .See also
*
Burnup .
*Isotopes of plutonium .External links
* [http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@na+@rel+plutonium,+radioactive NLM Hazardous Substances Databank – Plutonium, Radioactive]
Isotope|element=Plutonium
lighter=Plutonium-239
heavier=Plutonium-241
before=Plutonium-239 (n)Curium-244 (α)
Uranium-240 (EC)Neptunium-240 (β-)
after=Americium-240 "'(β)
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