A model for analysis of fuel behaviour in transients

Abstract For many applications, analysis of fuel element behaviour must take non-linear thermal, and elasto-plastic effects into account. This is particularly true if the fuel undergoes large deformations and rapid temperature transients. To meet this need a multi-dimensional fuel model based on finite element stress and thermal analysis has been developed. The model is solved for the transient temperature distribution by a step-by-step time incremental procedure. The temperature is then introduced into the elasto-plastic analysis as a thermal load and stresses and deformations are calculated. A model for treatment of creep and a special element for the gap between fuel pellet and cladding is incorporated together with semi-empirical procedures for calculating fission gas release, fuel pellet to cladding heat transfer coefficients, etc. The fuel model has been compared with both analytical solutions and in-reactor experimental results. The observed and predicted results are in good agreement.

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