Reactor Theory (Nuclear Parameters)DOE-HDBK-1019/2-93REACTIVITYREACTIVITYReactivity is a measure of the departure of a reactor from criticality. Thereactivity is related to the value of keff . Reactivity is a useful concept to predicthow the neutron population of a reactor will change over time.EO 1.8Given the number of neutrons in a reactor core and theeffective multiplication factor, CALCULATE the number ofneutrons present after any number of generations.EO 1.9DEFINE the term reactivity.EO 1.10CONVERT between reactivity and the associated value of keff.EO 1.11CONVERT measures of reactivity between the following units:a.Dk/kc.10-4Dk/kb.%Dk/kd.Percent millirho (pcm)EO 1.12EXPLAIN the relationship between reactivity coefficients andreactivity defects.Applicationof the EffectiveMultiplicationFactorWhen keff remains constant from generation to generation, it is possible to determine the numberof neutrons beginning any particular generation by knowing only the value of keff and the numberof neutrons starting the first generation. If No neutrons start the first generation, then No(keff)neutrons start the second generation. Equation (3-4) can be used to calculate the number ofneutrons after the completion of "n" generations.(3-4)Nn No keffnRev. 0NP-03Page 17
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