Advanced Analysis of Subcritical Neutron Noise Experiments

Erez Gilad, Chen Dubi, Benoit Geslot, Patrick Blaise

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

A novel method for direct and simultaneous estimation of the core kinetic parameters and its absolute reactivity is proposed. The method is based on the well known Feynman-Y method and is computationally intensive. The method does not rely on any pre-calculated or pre-measured physical quantity of the core, rather requires only the detector readings from an in-pile noise measurement and a set of delayed neutron group yields and the associated decay constants. The method is implemented and used for the analysis of subcritical configurations of the MAESTRO core in the MINERVE zero power reactor in order to measure its integral kinetic parameters,i.e., effective delayed neutron fraction β eff and the prompt neutron generation time Λ, in addition to the absolute reactivity ρ. Uncertainty analysis shows that the associated uncertainties are reasonably small. Additionally, Feynman-Y curves are calculated for small time gates (down to 10-5 s), revealing an asymptotic approach to negative values. This is used to extract the detectors' dead time assuming that detector count losses due to dead time are the main contribution for this phenomenon. Finally, a new random sampling technique is proposed for obtaining Feynman-Y curve. The random sampling method has the advantages of producing less fluctuating curves and eliminating temporal correlations between successive time gates. Its major disadvantage is its dependence on CPU intense computations. Nonetheless, this method is implemented and compared to standard successive sampling technique.
Original languageAmerican English
Title of host publicationM&C2017 - International Conference on Mathematics & Computational Methods Applied to Nuclear Science & Engineering
Subtitle of host publicationJeju ISland (Korea)
StatePublished - 16 Apr 2017

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