A concept for the assessment of dissimilar weldments in HTR steam piping is described. A combination of experiments and calculation shows that dissimilar metal welds between the ferritic steel X 20 CrMoV 21 1 and the austenitic alloy X 10 NiCrAlTi 32 20 can be operated for the design life of the component. The combination of reliable manufacturing and nondestructive testing assures that defects in weld joints will show only negligible crack growth. The leak before break criterion is fulfilled. The concept of assessment of dissimilar weldments is verified by the component test MINERVA.