EXTENDED MSM METHOD TO ESTIMATE THE REACTIVITY OF A SUB-CRITICAL CORE DRIVEN BY AN ACCELERATOR BASED NEUTRON SOURCE

¹ Laboratoire de Physique Subatomique et de Cosmologie IN2P3(CNRS)-Université Grenoble Alpes, 53 rue des Martyrs 38026 Grenoble Cedex, France
² Laboratoire de Physique Corpusculaire de Caen ENSICAEN/Université de Caen/CNRS-IN2P3, 6 bd Maréchal Juin, 14000 Caen, France
³ Institut de Physique Nucléaire d’Orsay CNRS-IN2P3/Univ. Paris Sud, 91406 Orsay, France
⁴ SCK-CEN, Belgian Nuclear Research Centre Boeretang 200, 2400 Mol, Belgium
⁵ Nuclear Fission Division, CIEMAT, Madrid, Spain
⁶ Commissariat à l’Énergie Atomique et aux Énergies Alternatives, DEN, DER/SPEX, 13108 Saint-Paul-lez-Durance, France

billebaud@lpsc.in2p3.fr
^* now at AREVA-NP, Lyon, France
^** now at The Binding Energy bvba, Gent, Belgium

Published online: 22 February 2021

Abstract

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.