Extended MSM method to estimate the reactivity of a sub-critical core driven by an accelerator based neutron source

A. Billebaud (1) , J.-L Lecouey (2) , T. Chevret (2, 3) , Sébastien Chabod (1) , X. Doligez (4) , A. Kochetkov (5) , A. Krasa (5) , F.-R Lecolley (2) , G. Lehaut (2) , N. Marie (2) , Nadia Messaoudi (5) , W. Uyttenhove (5) , G. Vittiglio (5) , J. Wagemans (5) , V. Becares (6) , D. Villamarin (6) , Frédéric Mellier (7)

1 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
2 LPCC - Laboratoire de physique corpusculaire de Caen
3 AREVA NP Lyon
4 IPNO - Institut de Physique Nucléaire d'Orsay
5 SCK-CEN - Centre d'Etude de l'Energie Nucléaire
6 CIEMAT - Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
7 CEA - Commissariat à l'énergie atomique et aux énergies alternatives

The Modified Source Multiplication method is used to determine an unknown reactivity level of a reactor from a known one if one has access to the detector counting for both levels when the reactor is fed by a constant neutron source like an Am-Be source. When available, an accelerator driven source, in continuous mode, can be useful as its intensity can be tunable and then adapted to the experimental conditions. However, in that case, the MSM technique must be extended to account for an external source whose intensity, energy and angular distributions can vary from one measurement to another. In this paper, this Modified Multi-Source Multiplication (MMSM) method is applied to measurements done during the FREYA project in the GUINEVERE facility, operated with the GENEPI-3C accelerator providing a mixture of (D,T) and (D,D) neutrons. The monitoring of these sources through the detection of the associated charged particles allows the calculation of the MMSM factors and the estimate of the reactivity values. The results are compared in different configurations with the reactivity obtained with an Am-Be source or in dynamic measurements performed with GENEPI-3C. Their excellent agreement shows the possibility of using such accelerator-based neutron sources for MSM measurements when they are correctly monitored. This is of great interest for deep sub-critical level characterization for which detector count rates per source neutrons might be low.

Domains: Nuclear Experiment [nucl-ex]; Physics [physics]

A. Billebaud, J.-L Lecouey, T. Chevret, Sébastien Chabod, X. Doligez, et al.. Extended MSM method to estimate the reactivity of a sub-critical core driven by an accelerator based neutron source. International Conference on Physics of Reactors 2020: Transition to a Scalable Nuclear Future (PHYSOR 2020), Mar 2020, Cambridge, United Kingdom. pp.08005, ⟨10.1051/epjconf/202124708005⟩. ⟨hal-03016382⟩