Startup neutron source: Difference between revisions

Revision as of 10:02, 28 March 2010

Revision as of 10:10, 28 March 2010

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The sources can be of two types:<ref name="nucleng">http://books.google.com/books?id=EMy2OyUrqbUC&pg=PA27&dq=neutron+startup+source&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&num=50&as_brr=3&cd=4#v=onepage&q=neutron%20startup%20source&f=false</ref>

* '''Primary sources''', used for startup of a fresh reactor core; conventional [[neutron source]]s are used, usually [[californium]]-252 ([[spontaneous fission]]), or [[plutonium-238]]-beryllium or [[americium]]-beryllium (&alpha;,n [[nuclear reaction]]s). The primary sources are removed from the reactor after the first fuel campaign, usually after few months. Primary sources are subject to [[neutron capture]]; exposition to thermal neutron flux in an operating reactor reduces their lifetime.

** [[Californium]]-252 ([[spontaneous fission]])

** [[Plutonium-238]]-beryllium, [[Plutonium-239]]-beryllium or [[americium]]-beryllium (&alpha;,n [[nuclear reaction]]s).

* '''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. The exposition to thermal neutrons also serves to maintain the source activity (the radioactive isotopes are both burned and generated in neutron flux).

** [[Antimony|Sb]]-[[Beryllium|Be]] [[photoneutron]] source; antimony [[neutron activation|becomes radioactive]] in the reactor and its strong gamma emissions (1.7 MeV for ¹²⁴Sb) interact with [[beryllium-9]] by an (&gamma;,n) reaction and provide [[photoneutron]]s. In a PWR reactor one neutron source rod contains 160 grams of antimony, and stay in the reactor for 5-7 years.<ref>http://books.google.com/books?id=SJOE00whg44C&pg=PA147&dq=neutron+startup+source&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&num=50&as_brr=3&cd=22#v=onepage&q=neutron%20startup%20source&f=false</ref> The sources are often constructed as an antimony rod surrounded by beryllium layer and clad in [[stainless steel]].<ref name="tpub">http://www.tpub.com/content/doe/h1019v1/css/h1019v1_108.htm</ref><ref>http://www.lib.ncsu.edu/specialcollections/digital/text/engineering/reactor/murray/MurNBabneutron040953.html</ref> Antimony-beryllium [[alloy]] can be also used.

** [[lead|Pb]]-[[beryllium|Be]] source

[[Boron-11]] can be added to the fuel; it emits neutrons by the (&alpha;,n) reaction to [[nitrogen-14]]. [[Deuterium]] in heavy water emits neutrons by (&gamma;,n) reaction to ¹H.<ref name="tpub"/>

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<references/>

[[Category:NuclearNeutron technologysources]]

[[Category:Neutron]]