Refined Control Rod Worth Estimation by Kinetics Equations with Included Photoneutrons

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Abstract

In this paper we show that in the BR2 reactor, which is reflected and moderated by a beryllium matrix, the reactivity worth of the control rods is strongly influenced by the delayed photoneutrons, emitted after (gamma,n)– reactions of photons with beryllium. To analyze this reactivity worth, important to evaluate the correct value of the shut down margin, refined estimations of the control rod worth are performed using the reactor kinetics equations including delayed photoneutron groups. The delayed photoneutron parameters were experimentally determined in the BR02 mock-up reactor. The reactivity worth of the control rods are derived from nuclear measurements, which have been performed during several BR2 shutdowns in 2009. The importance of the photoneutrons for the reactivity worth determination depends on the chosen analysis method. The reactivity worth from the rod-drop tests is estimated using an approximate equation for the neutron density decay, the validity of which was verified by comparison with the numerical solutions, obtained by the transient code PARETV7.5/ANL. The contribution of the photoneutrons into the reactivity worth, analyzed by this method for the BR2 reactor conditions is 2%. Neglecting the photoneutrons contribution in the inhour equation leads to underestimation of the rod worth by 18%.

Details

Original languageEnglish
Title of host publicationPhysor 2010
Place of PublicationLaGrange Park, IL, United States
StatePublished - 10 May 2010
Event2010 - PHYSOR - Pittsburgh, United States

Conference

Conference2010 - PHYSOR
CountryUnited States
CityPittsburgh
Period2010-05-092010-05-14
Internet address

Keywords

  • control rod worth, scram, reactor period, photoneutrons, MCNPX

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