Assessment of fuel rod performance codes under ramp scenarios investigated within the SCIP project

► This paper shows a comparison of the thermo-mechanical responses of ALCYONE V1.1, FALCON-PSI, FRAPCON-3 v3.3 and STAV7.3 to experimental data for advanced cladding materials when submitted to anticipated loadings from pellet-mechanical interactions. Such comparison has been expressed in terms of cladding oxidation, diameters and elongation. Additionally, code-to-code comparisons of some key variables (i.e., fuel temperature, contact pressure, hoop and axial stresses, etc.) highlighted systematic tendencies of the codes and supported the observations made. ► Predictability of clad oxidation was certainly scattered among the codes and while some codes showed reasonable accuracy, other results were notably deviated. As for diameters, most of the codes were capable of qualitatively capturing the axial profile, and showed consistency between diameters and hoop stress and strain predictions. Elongation estimates were generally poor, and were rather far from measurements in most cases (even the trends observed just vaguely followed by the codes). ► All the codes showed areas in which further modeling or model enhancement is recommended. ► Some further experimental information seems to be necessary in several regards either to enhance the present modeling capabilities or to extend the codes validation: material properties, particularly creep/plasticity laws and corrosion rates, should be more extensively characterized under steady state and power transients would be valuable (stress relaxation tests as well as “lift-off” experiments could provide significant information on creep/plasticity laws); gas swelling effects and kinetics as a key phenomenon for fuel response to transients; measurements of variables like fuel temperature, internal pressure and on-line cladding elongation would be desirable.