Insertion and drop of control rod in assembly simulations and parametric analysis

We present in this paper some results obtained with a numerical model of control rod behaviour. Drop time and insertion force are studied by means of a large parametric analysis. Fuel assembly deflection is the main parameter of this study. Several loads are taken into account in control rod displacement calculation: fluid load, gravity and friction force against the guide. Simulations are compared to measurements carried out in a full-scale prototype. The analysis of drop calculation shows that the friction cannot be neglected when fuel assembly is bowed. The main result for insertion force calculation is the important sensitivity to data entry. Determining exact deflection all along assembly with precision is needed. Otherwise, approximated friction force is obtained. (author)