Thermo-mechanical analysis for metal fuel rod under transient operation condition

Computational models for analyzing in-reactor behavior of metallic fuel pins in liquid-metal reactors under transient conditions are developed and implemented in the TRAnsient thermo- Mechanical Analysis Code for metal fuel rod under transient operation condition (TRAMAC). Not only the basic models for fuel rod performance under transient condition, but also some sub-models used for transient condition are installed in TRAMAC. Among the models, fission gas release model, which takes multibubble size distribution into account to characterize the lenticular bubble shape and the saturation condition on the grain boundary and cladding deformation model have been mainly developed based on the existing models in MACSIS code. Finally, cladding strains are calculated from the amount of thermal creep, irradiation creep, irradiation swelling. The cladding strain model in TRAMAC well predicts the absolute magnitudes and general trends of their predictions compared with those of experimental data. TRAMAC results for FM-1,2,6 pins are more conservative than experimental data and relatively reasonable than those of FPIN2. From the calculation results of TRAMAC, it is apparent that the code is capable of predicting fission gas release, and cladding deformation for LMR metal fuel. The results show that in general, the predictions of TRAMAC agree well with the available irradiation data