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    STP1608

    Exploration of the 1 keV–1 MeV Neutron Energy Range Using Zirconium Dosimeters

    Published: 2018


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    Abstract

    The 1 keV to 1 MeV neutron energy range is of major importance for neutron spectrum reconstruction at any particular location in a reactor. Typical applications may be neutron flux assessment in order to anticipate embrittlement of pressure water reactor vessels, study of material damage under high–dose irradiation in materials testing reactors, or experimental data for feedback on various cross-section evaluations. Up to now, thermal and fast ranges of the neutron spectrum could be determined accurately by using dosimeters with adequate energy sensitivity. However, there is no proper dosimeter to investigate the intermediate energy domain. The purpose of this paper is to demonstrate the possibility of detecting the neutron flux between 1 keV and 1 MeV by irradiating zirconium-92 (92Zr) and 94Zr samples under a boron nitride filter, which reduces thermal neutron contribution. This article describes a specific irradiation of zirconium dosimeters as well as experimental results obtained by gamma spectrometry or accelerator mass spectrometry. This irradiation is simulated with the TRIPOLI-4® Monte-Carlo neutron transport code. Nuclear reactions of interest are 94Zr(n, γ)95Zr→niobium-95 (95Nb)→molybdenum-95 (95Mo) (stable) and 92Zr(n, γ)93Zr (quasi-stable). Experimental values of 95Zr activity and 93Zr/92Zr isotopic ratio are compared to calculation results. After reviewing all available evaluations for nuclear data, a comparison is made using radiative capture cross sections from the Evaluated Nuclear Data File, ENDF/BVII.1 that are the most accurate. Finally, uncertainties are obtained by combining those from both experimental and nuclear data. This work demonstrates the feasibility of 1 keV to 1 MeV neutron detection by using 92Zr or 94Zr(n, γ) reactions (or both) and introduces an original post–irradiation analysis for reactor dosimetry based on accelerator mass spectrometry. It also reveals that more precise evaluations of 92Zr and 94Zr(n, γ) cross sections are required in order to improve calculation/experiment values.
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    Keywords:

    dosimetry, epithermal neutron, zirconium, accelerator mass spectrometry, cross section, ZIMA experiment, OSIRIS reactor, TRIPOLI-4® Monte-Carlo code


    Author Information:

    Thiollay, Nicolas
    CEA/Cadarache, DEN/DER/SPEx/LDCI, Cadarache, Saint Paul lez Durance,

    Sergeyeva, Victoria
    CEA/Cadarache, DEN/DER/SPEx/LDCI, Cadarache, Saint Paul lez Durance,

    Lyoussi, Abdallah
    CEA/Cadarache, DEN/DER/SPEx/LDCI, Cadarache, Saint Paul lez Durance,

    Domergue, Christophe
    CEA/Cadarache, DEN/DER/SPEx/LDCI, Cadarache, Saint Paul lez Durance,

    Destouches, Christophe
    CEA/Cadarache, DEN/DER/SPEx/LDCI, Cadarache, Saint Paul lez Durance,


    Committee/Subcommittee: E10.05

    DOI: 10.1520/STP160820170045