Calibration and Validation of thermal fuel behaviour models based on the first case of the first IAEA CRP FUMEX

Results of a model calibration-dedicated part of the project, entitled 'Comprehensive Verification of the FALCON Code for Calculation of Nuclear Fuel Temperature' are presented. For sensitivity analysis, Case 1 of the past IAEA CRP FUMEX is used. Considered are the effects caused by: correlations used for the fuel thermal conductivity; power maneuvering; fuel densification; treatment of the sinterable- and open- as-fabricated fuel porosity. An alternative correlation for fuel thermal conductivity is introduced into the code. The uncertain parameters of a few temperatures' prediction-related models and modeling assumptions are refined. After the calibration, essentially improved agreement with the data for FUMEX Case 1 is shown. A prerequisite for the following successful verification of the advanced version of the FALCON MOD01 code as applied to fuel temperature during both steady-state- and transient- irradiation conditions is fulfilled through the current calibration.