Stress-driven flow of impurities and its implications for embrittlement of structural components in nuclear applications

Embrittlement of load-carrying components in nuclear applications is reason for concern. While components are fabricated from materials that have sufficient initial ductility, service conditions can degrade materials properties, sometimes leading to embrittlement. A drop in ductility is associated with a lowering of the material fracture toughness, that is, a lowering of the resistance to crack growth. This problem has been investigated in detail for the case of nuclear pressure vessel steels and is also of concern for other nuclear components. A means of assessing the amount of embrittlement due to the collection or rejection of various types of solute atoms near a crack tip or other stress field has been developed. The model can incorporate the effects of radiation enhancement in the embrittlement process by alteration of the relevant materials parameter. The effects of radiation enhancement are found to be significant.