This paper presents simulation results of earlier fuel melting tests (xM3 and HBC4) performed under the power-to-melt-and-maneuverability (P2M) simulation exercise organized within the Organisation for Economic Co-operation and Development (OECD)/Nuclear Energy Agency (NEA) framework for irradiation experiments. The simulations were performed using the single-rod performance analysis code FRAPCON/FRAPTRAN as a contribution of the Central Research Institute of Electric Power Industry (CRIEPI) to the P2M simulation exercise. To this end, the base irradiation of each sample was simulated using FRAPCON software, and the calculated result was used to define the initial state of the transient simulations; the xM3 and HBC4 ramp tests were simulated using FRAPTRAN. Fuel melting was not predicted for xM3, and the melting radius was underestimated for HBC4 using the original version of FRAPTRAN. The value of the fuel/cladding gap conductance was modified to obtain results that satisfy the experimental measurement of the melting radius.

In this paper, the simulation results are compared with experimental results, and the causes for discrepancy between the simulation and experiment results are discussed. The necessary improvements for FRAPTRAN to achieve a better simulation of fuel melting are also discussed. These results can help calibrate codes against high-temperature behavior and improve fuel melting modeling toward the planned P2M power ramp tests.