Startup neutron source: Difference between revisions

Revision as of 14:38, 10 May 2012

Revision as of 00:03, 26 June 2012

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The sources can be of two types:<ref name="nucleng">{{cite book|url=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 |title=Nuclear Engineering Handbook |author=Ken Kok|page=27|publisher=CRC Press|date=2009 |isbn=1-4200-5390-6}}</ref>

* '''Primary sources''', used for startup of a fresh reactor core; conventional [[neutron source]]s are used. The primary sources are removed from the reactor after the first fuel campaign, usually after few months., Primary sources are subject toas [[neutron capture]]; exposureresulting tofrom the thermal neutron flux in an operating reactor changes the composition of the isotopes used, and thus reduces their useful lifetime as neutron sources.

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

** [[Plutonium-238]]-[[beryllium]], [[plutonium-239]]-beryllium or [[americium]]-beryllium (α,n [[nuclear reaction]]s).

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

AWhen [[plutonium-238]]/beryllium primary sourcesources can beare utilized. As plutonium-238 would undergo neutron capture and transmutation when subjected to intense [[thermal neutron]] flux, which would dramatically shorten the source lifetime, the sourcesthey can be either affixed to some [[control rod]]s which andare removed from the reactor when it is powered, or clad in a [[cadmium]] alloy, which is opaque for theto thermal neutrons (reducing transmutation of the plutonium-238 by neutron capture) but transparent for theto [[fast neutron]]s produced by the source.<ref name="pat1"/>

Some neutron sources also serve as additional sources of [[delayed neutron]]s; these serve to dampen the response rate of reactor power to control rods and power transients, allowing safer and more stable operation.