This paper explores the possibilities of computer modeling (application of finite element method) and detection of defects by ultrasonic control without destruction. The defects of interest are occurring in the early stage of creep (secondary creep) in steel pipes (P91) used in thermal power plants. The commercial FEMAP software was used to show the layout and behavior of strain caused by the creep on the tube model, and commercial PZFlex software was used for ultrasound analysis. Norton's law was used to define the creep in the 3D model of pipes. The adopted terms and coefficients of the Norton's Law were originally used in Microsoft Excel at varying degrees of stress in order to establish certain trends that approximate the creep propagation in the model. Then the Norton's Law coefficient's were used in the commercial FEMAP software for creep analysis on the 3D model of the tube. The conducted analysis shows the type of deformation that occurs on the 3D model of the tube. The analysis also shows the area of the greatest strain on the 3D model and the layout and intensity of the stress that is occurring. The analysis in the commercial FEMAP software shows very well the effects of creep on the model and the presence of critical spots. Ultrasonic analyses were made on two models with one defect embedded in the models. Then the surface of the defect was gradually decreased for the purpose of testing the capabilities of the model and constructed transducers. Finally, simulation with an array of defects was made in order to approximate the creep damage in the tube model. Based on the results obtained, a conclusion was made on the possibilities of using ultrasonic analysis to detect the presence of creep. The analysis carried out in the commercial PZFlex software shows very well the influence of the present defects in the tube model on the spread of the sound waves