Residual stress in a laser welded EUROFER blanket module assembly using non-destructive neutron diffraction techniques

• Residual stresses were determined in a welded EUROFER blanket assembly with integrated cooling channels.
• Good agreement was seen between experimentally determined and predicted stresses.
• We show that microstructure changes that occur in EUROFER steels during welding must be considered for residual stress determination.
• An experimental route is proposed for validation of predicted stresses in reactor components using non-destructive diffraction techniques.

Whilst the structural integrity and lifetime considerations in welded joints for blanket modules can be predicted using finite element software, it is essential to prove the validity of these simulations. This paper provides detailed analysis for the first time, of the residual stress state in a laser-welded sample with integral cooling channels. State-of-the-art non-destructive neutron diffraction was employed to determine the triaxial stress state and to understand microstructural changes around the heat affected zone. Synchrotron X-ray diffraction was used to probe the variation of strain-free lattice reference parameter around the weld zone allowing correction of the neutron measurements. This paper details an important experimental route to validation of predicted stresses in complex safety-critical reactor components for future applications.