Study of the linearity of CABRI experimental ionization chambers during RIA transients

CABRI is an experimental pulse reactor operated by CEA at the Cadarache research center and funded by the French Nuclear Safety and Radioprotection Institute (IRSN).For the purpose of the CABRI International Program (CIP), operated and managed by IRSN under an OECD/NEA framework it has been refurbished since 2003 to be able to provide experiments in prototypical PWR conditions (155 bar, 300 DC) in order to study the fuel behavior under Reactivity Initiated Accident (RIA) conditions.This paper first reminds the objectives of the power commissioning tests performed on the CABRI facility. The design and location of the neutron detectors monitoring the core power are also presented.Then it focuses on the different methodologies used to calibrate the detectors and check the consistency and co-linearity of the measurements.Finally, it presents the methods used to check the linearity of the neutron detectors up to the high power levels (~20 GW) reached during power transients. Some results obtained during the power tests campaign are also presented.