Monitoring the fast neutrons in a high flux: the case for 242Pu fission chambers

Philippe Filliatre, Christian Jammes, Ludovic Oriol, Benoit Geslot, Ludo Vermeeren, Marcel Wéber

    Research outputpeer-review


    Fission chambers are widely used for on-line monitoring of neutron fluxes in irradiation reactors. A selective measurement of a component of interest of the neutron flux is possible in principle thanks to a careful choice of the deposit material. However, measuring the fast component is challenging when the flux is high with a significant thermal component. The main problem is that the isotopic content of a material selected for its good response to fast neutrons evolves with irradiation, so that the material is more and more sensitive to thermal neutrons. Within the framework of the FNDS (Fast Neutron Detector System) project, we design tools that simulate the evolution of the isotopic composition and fission rate for several deposits under any given flux. In the case of a high flux with a significant thermal component, 242Pu is shown to be the best choice for measuring the fast component, as long as its purity is sufficient. If an estimate of the thermal flux is independently available, one can correct the signal for that component. This suggests a system of two detectors, one of which being used for such a correction.
    Original languageEnglish
    Title of host publicationFirst International Conference on Advancements in Nuclear Instrumentation, Measurement methods and their Applications (ANIMMA), 2009
    Place of PublicationPiscataway, NJ, United States
    StatePublished - 8 Jul 2010
    Event2009 - ANIMMA : 1st International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications - CEA, Marseille
    Duration: 7 Jun 200910 Jul 2009


    Conference2009 - ANIMMA
    Abbreviated titleANIMMA

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