Talk:Plutonium-239

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Possible error?

At U-236 it says: "When 235U absorbs a thermal neutron, one of two processes can occur. About 82% of the time, it will fission; about 18% of the time, it will not fission, instead emitting gamma radiation and yielding 236U"

At Pu-240 it says: "About 62% to 73% of the time when 239Pu captures a neutron, it undergoes fission; the remainder of the time, it forms 240Pu."

At Pu-239 it says: "239Pu has a higher probability for fission than 235U and a larger number of neutrons produced per fission event, so it has a smaller critical mass."

I'm no nuclear physicist but methinks there's an error there somewhere. 190.100.175.35 (talk) 06:38, 5 August 2020 (UTC)[reply]

See neutron cross section. Plutonium is about twice as likely as 235-U to capture a neutron in the first place, so it has a higher overall probability to be induced to fission. VQuakr (talk) 06:54, 5 August 2020 (UTC)[reply]

Why no Spontaneous Fission rate?

Military weapons are "poisoned"(less reliable) when several percent of Pu240 accumulates. This occurs from neutrons from Pu239 SF and subsequent fissions and delayed neutrons in the pit. For this to occur with fast neutrons would require a significant Spontaneous Fission rate. What is the SF rate? [Is it US government censorship? Or does noone know this information (hard to believe.)] The upcoming multi Trillion dollar replacement of older Plutonium weapons by the US Pentagon is significant and the SF rate is pertinent. Also no mention of health hazards from neutrons, which goes through most shielding. Rem thermal neutrons decay. TaylorLeem (talk) 18:46, 13 February 2021 (UTC)[reply]

Economics of Plutonium

"[..]the ability to produce large amounts of nearly pure 239Pu more cheaply than highly enriched weapons-grade uranium-235, led to its use in nuclear weapons and nuclear power plants."

Modern prices for plutonium are around $5 million per kilo, while HEU is around $25,000 per kilo. Were the economics different in WWII or the early Cold War? Perhaps this section needs to be expanded a bit? NelC (talk) 15:34, 4 August 2025 (UTC)[reply]