Abstract
The study of Reactivity Initiated Accidents (RIA) is important to determine up to which limits nuclear fuels can withstand such accidents without clad failure. The CABRI International Program (CIP), conducted by IRSN under an OECD/NEA agreement, has been launched to perform representative RIA Integral Effect Tests (IET) on real irradiated fuel rods in prototypical Pressurized Water Reactors (PWR) conditions. For this purpose, the CABRI experimental pulse reactor, operated by CEA in Cadarache, France, has been strongly renovated, and equipped with a pressurized water loop. The behavior of the test rod, located in that loop in the center of the driver core, is followed in real time during the power transients thanks to the hodoscope, a unique online fuel motion monitoring system, and one of the major distinctive features of CABRI. The hodoscope measures the fast neutrons emitted by the tested rod during the power pulse with a complete set of 153 Fission Chambers and 153 Proton Recoil Counters. During the CABRI facility renovation, the electronic chain of these detectors has been upgraded. In this paper, the performance of the new system is presented describing gain calibration methodology in order to get maximal Signal/Noise ratio for amplification modules, threshold tuning methodology for the discrimination modules (old and new ones), and linear detectors response limit versus different reactor powers for the whole electronic chain.
Highlights
One of the most challenging problems of our day, in nuclear industry, is to maintain Nuclear Power Plants (NPP) in safe working conditions during all their life
CABRI core was built in order to determine up which limits fuel rod cladding does not fail under power excursion due to Reactivity Initiated Accident (RIA) accident
An online fuel motion measurement system named hodoscope, which aims at analyzing the fuel motion deduced from the detection of fast neutrons emitted by the tested rod, in real time during the transient
Summary
One of the most challenging problems of our day, in nuclear industry, is to maintain Nuclear Power Plants (NPP) in safe working conditions during all their life. CABRI core was built in order to determine up which limits fuel rod cladding does not fail under power excursion due to RIA accident. A non-destructive examination facility, for performing X-ray radiography and tomography imaging before and after power transient thanks to a linear accelerator; An online fuel motion measurement system named hodoscope, which aims at analyzing the fuel motion deduced from the detection of fast neutrons emitted by the tested rod, in real time (with a time step of 1ms) during the transient. Proton Recoil Counters (PR) are better suited for low power measurement while 237Np Fission Chambers (FC) are dedicated to high power monitoring Both detectors measure the fast neutrons coming from the test rod and from the CABRI driver core fuel.
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