Synthesis of CABRI REP-Na

J. Papin, M. Petit, F. Lemoine, F. Jeury*, C. Marquié, D. Moulin*, C, Doederlein*, J.M. Frizonnet, J. Desquines, V. Bessiron, E. Federici, V. Georgenthum, B. Cazalis, J. Charpenel, (*CEA/DEN), Rapport Technique DPAM 2003/0009

The CABRI REP-Na programme realised in cooperation with EDF, has been devoted to the study of the behaviour of highly irradiated fuel (UO2 and MOX) submitted to fast power transients simulating Reactivity Initiated Accidents (RIA) of PWRs.

The general objectives were to identify and quantify the main physical phenomena which can lead to rod failure and fuel ejection during the first phase of a RIA transient, that of strong pellet-clad mechanical interaction (PCMI) without significant clad heat-up (limitation due to the use of sodium as coolant). In particular, the main goals were to:
- investigate the impact of the high burn-up fuel (up to 64 GWd/t, maximum pellet value) and high corrosion level of the cladding (up to about 100 mm) such as anticipated in the future core loadings at that time,
- determine whether irradiated MOX fuel exhibits a specific behaviour under RIA conditions.

The CABRI REP-Na programme with its first ten tests REP-Na1 to REP-Na10, provided an important extension of the knowledge of the physical phenomena relatively to PWR rods behaviour submitted to power transients, and allowed developments for an improved modelling and validation of the SCANAIR code.

The extensive evaluation of the experimental results and the theoretical interpretation of the tests are described in the different chapters of this synthesis document, together with the results of the support test programmes, allowed to derive main outcomes reported in the Executive Summary of the report.

The CABRI International Programme (CIP) already launched in 2000 (two first tests performed in 2002), will provide under typical pressurised water conditions, relevant additional knowledge relative to high burn-up UO2 and MOX advanced fuels.