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The polonium used in the urchin initiator was created at Oak Ridge National Laboratory and then extracted and purified as part of the Dayton Project under the leadership of Charles Allen Thomas. The Dayton Project was one of the various sites comprising the Manhattan Project .
Ultimately, polonium-based neutron initiators were used in both the gun-type Little Boy and the implosion-type Fat Man used in the atomic bombings of Hiroshima and Nagasaki respectively. The fact that polonium was used as an initiator was classified until the 1960s, but George Koval , a technician with the Manhattan Project's Special Engineer ...
Polonium is a chemical element; ... The fact that a polonium-beryllium (Po-Be) initiator was used in the gun-type nuclear weapons was classified until the 1960s.
Ultimately, polonium-based neutron initiators were used in both the gun-type Little Boy and the implosion-type Fat Man used in the atomic bombings of Hiroshima and Nagasaki respectively. The fact that polonium was used as an initiator was classified until the 1960s, but George Koval , a technician with the Manhattan Project's Special Engineer ...
So there might be a third basic component to their atomic bomb besides nuclear core and confining tamper: an initiator - a Ra + Be source or, better, a Po + Be source, with the radium or polonium attached perhaps to one piece of the core and the beryllium to the other, to smash together and spray neutrons when the parts mated to start the chain ...
Although the weapon's designers thought that simply bringing a critical mass together would be sufficient, Serber suggested that the design should also include an initiator. A polonium-210-beryllium initiator was chosen because polonium 210 has a 140-day half life, which allowed it to be stockpiled, and it could be obtained from naturally ...
A polonium-beryllium modulated neutron initiator, known as an "urchin", [213] was developed to start the chain reaction at precisely the right moment. [214] This work on the chemistry and metallurgy of radioactive polonium was directed by Charles Allen Thomas of the Monsanto Company and became known as the Dayton Project. [215]
A startup neutron source is a neutron source used for stable and reliable initiation of nuclear chain reaction in nuclear reactors, when they are loaded with fresh nuclear fuel, whose neutron flux from spontaneous fission is insufficient for a reliable startup, or after prolonged shutdown periods.