Assessment of reactor pressure vessel multilayer weld metal

Fracture toughness of the multi-layer belt-line welding seam of the Biblis C reactor pressure vessel was characterized by the test standard ASTM E1921. The reference temperature, T₀, was determined for different thickness positions of the multi-layer welding seam. Additionally, the influence of the specimen orientation on T₀ was investigated. In contrast to the T-S orientation (crack extension through the thickness) the crack front of the T-L oriented specimens (crack extension in welding direction) penetrates several welding beads. By means of fractographic and metallographic analyses it was shown that the distribution of the crack initiation sites is not necessarily correlated to the structure of the different welding beads along the crack front. Furthermore, it was found that the scatter of the K_Jc values determined with T-S specimens is significantly higher than in case of the T-L specimens. T₀ values measured at different thickness locations of the multi-layer welding seam vary in a range of about 40 K. (authors)