Numerical Simulation of Fuel Pellet Cladding Interaction in Nuclear Reactor

Under reactivity-initiated accident conditions (RIA), due to the expansion of the pellet, the pellet and the cladding have a mechanical interaction (PCMI). The extrusion of the pellet to the cladding causes the cladding to produce greater hoop stress and hoop strain, which leads to damage. The extrusion of the core block to the cladding causes the cladding to produce greater hoop stress and hoop strain, which leads to damage. Due to the complex internal environment of the reactor, the difficulty and cost of experiment implementation are high, so a simulation program in the reactor was designed. By comparing the calculation results of the simulation scheme with the data obtained in the reactor experiment, it is proved that the simulation calculation results are in good agreement with the experimental data in the reactor, and the rationality of the simulation scheme is verified. Based on the characteristics of the reactor, a set of external experiment equipment was designed, and the corresponding finite element model was established. In order to save the cost of the experiment and improve the effectiveness of the experiment, a simulation analysis outside the reactor was carried out. By analyzing the results of the simulation calculation outside the reactor, it is found that the core material, cladding temperature, compression rate, tensile load, friction coefficient and the cladding hoop stress and hoop strain have a certain relationship: (1) The choice of core block material affects the reactor. The overall law of hoop stress–strain in the external simulation results basically has no effect. (2) The temperature of the cladding has a significant effect on the hoop stress peak of the cladding. (3) The compression rate has a significant effect on the time for the cladding to reach the hoop stress peak Influence. (4) Tensile load will affect the starting position of the hoop stress–strain of the cladding. (5) The friction coefficient has a significant influence on the stress and strain trend of the cladding. Based on the analysis of the simulation calculation results outside the reactor, the outside experiment can be carried out more effectively, and it can provide guidance and basis for the outside experiment.