04 - Lecture 4: MED General Groves and the Manhattan...

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Lecture 4: MED General Groves and the Manhattan Project A. Uranium Fission: Berlin, 1938/39 several scenarios running through people's minds slow vs fast neutron (u238 vs u235) slow neutrons are the ones we see all the time in regular day. if the neturons are coming out of fission are slow neutrons, and if we are using natural uranium, what you could get is a nuclear reaction. IE: slow neutrons + natural uranium (99.3% u238 + .7% u235) = a nuclear reactor (probably) via slow (moderated) chain-reaction fission of u235 if the neutrons coming out of the fission are slow ones, then you could make power. IF the neutrons are fast neutrons, they might be able to be used for a chain reaction. you could get a bomb, BUT the u238 will absorbed. nothing interesting may happen -- or maybe transuranic elements after all: plutonium! the navy was interested, the army was not so much. looks like a bomb will not be such a threat. the big question is . .. when he builds his reactor to get his reaction, he will begin to determine on how many neutrons on average come out. he wants a chain reaction that can control it and not blow up. eventually we will see the neutrons are going so fast, you can get 80 billionth of a second, to result in an explosion. neutrons have to be going fast enough or you will explode, and it'll come apart. step by step in the manhattan project, by 1944 they realize they wont know how big itll be before they blow it up. 2. Winter (Feb-March) 1940 to Winter (Feb-March) 1941 A. (Fast) Neutrons + U235 = a Weaponizable Fission Bomb (seen in early 1940) – between february march 1940 and 1941, it became clear that there would be two ways to make an atomic bomb, and they were both possible. by march 1940, american scientists were thinking, they didnt think it would be possible - we dont have to be afraid of a german bomb. KNOW PEOPLE that worked on bomb. no one had set down to think about neutrons and pure u235 because no one thought you could get the pure u235. FRISCH AND PERLS AT BIRGMINHAM in england thought of this: what no one saw in 1939: fast neutrons + pure u23 (size of a baseball or golf ball). = nuclear explosion! maybe, if there are enough neutrons for a chain reaction.
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B. Neutrons + U238 in a Nuclear Reactor = Plutonium (Pu) Pu239 + Neutrons = a Weaponizable Fission Bomb (seen by early 1941): Discovered at the Rad Lab (by MacMillan, Abelson, Seaborg , et al.) neutrons + u238 in a nuclear reactor = plutonium. pu239+neutrons = a weaponable fission bomb (seen by 1941): discovered at the rad lab by MACMILLAN, ABELSON, SEABORG. NUCLEAR REACTOR can produce plutonium! know how. people at berkeley found this out. world war ii had started. they called it "the product" in public. plutonium 239, like uranium 235, will fission in the same way.
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04 - Lecture 4: MED General Groves and the Manhattan...

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