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removed two lines of "primary sources" which were in error (intrinsic neutron sources during operation, not startup sources) |
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** [[americium-241]] & beryllium, (α,n) [[Nuclear reaction|reaction]]
** [[polonium]]-210 & beryllium, (α,n) [[Nuclear reaction|reaction]]
** [[radium]]-226 & beryllium, (α,n) [[Nuclear reaction|reaction]]<ref name="tpub" />
When [[plutonium-238]]/beryllium primary sources are utilized, they can be either affixed to [[control rod]]s which are removed from the reactor when it is powered, or clad in a [[cadmium]] alloy, which is opaque to thermal neutrons (reducing transmutation of the plutonium-238 by neutron capture) but transparent to [[fast neutron]]s produced by the source.<ref name="pat1" />
* '''Secondary sources''', originally inert, become radioactive and neutron-producing only after [[neutron activation]] in the reactor. Due to this, they tend to be less expensive. Exposure to thermal neutrons also serves to maintain the source activity (the radioactive isotopes are both burned and generated in neutron flux).
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