The Development of Finite Element Model for Pellet-Cladding Mechanical Interaction

This paper studies a FEA(Finite Element Analysis) model to describe PCMI under a power ramp and pressure loading conditions. From this PCMI model, the stress fields of pellet and cladding are evaluated. In order to compute the stress and strain fields in the cladding which were failed under the power ramp, this model might be extended to include the missing chip shape which occurred in the process of assembling or manufacturing of fuel rod. This missing chip of pellet has an affects on the temperature and the stress of the cladding in the vicinity of the chip edge so that the possibility of fuel failure is increased during the power ramp. The pellet fragmentation can be also accounted because the fuel cracking occurs immediately after reactor start-up and plays an important role in relaxing stresses in pellet but escalating the stress in cladding