Comparison of Experimental and Numerical Analysis Data for BMI Mock-Up With Dissimilar Metal Welds

During the last decade, several defects due to primary water stress corrosion cracking (PWSCC) have been reported at bottom-mounted instrumentation (BMI) and control rod drive mechanism nozzles. The exact locations were dissimilar metal weld parts which are greatly important because the cracking could lead to leakage of primary coolant. The PWSCC of BMI mock-up’s penetration with dissimilar metal welds was examined by using doped steam test method by Korea Atomic Energy Research Institute. In this work, numerical analyses are performed for the same environment condition with the doped steam test. With respect to the numerical analyses, heat transfer analyses are carried out based on thermal conduction. The welding paths are simulated by using lumped path method for conservative evaluation and model change (remove/rebirth) method. Then residual stress analyses are conducted using the heat transfer analysis results, in which annealing effect of welding process simulation is considered for resetting the plastic deformation. However, the plastic behaviour of steels during phase transformations is not considered with experimental data. In addition, the consequence of weld residual stress that is known as the cause of PWSCC is being investigated.