Status of U.S. reduced activation bainitic steel

Bainitic ferritic steels containing 2.25-3wt.% chromium are one of the candidate materials for lifetime structural components in fusion reactors, such as vacuum vessels or structural rings. These steels offer high-temperature properties, good weldability, and potentially low capital cost (Klueh et al., 1997; El-Guebaly et al., 2013; Rowcliffe et al., 2018). Although there are several other candidates for the vacuum vessel, such as high manganese containing austenitic stainless steels, RAFMs, low-alloy ferritic steels, and some bainitic steels (El-Guebaly et al., 2013), a reduced-activation bainitic steel based on Fe-3Cr-3W-0.2V-0.1Ta-Mn-Si-C (wt.%, so-called “3Cr-3WVTa”) is a strong candidate for fusion applications. This steel also meets the design requirements for the vacuum vessel material: (1) produce only low-level radioactive waste, (2) generate low levels of decay heat, (3) consist of a fracture-resistant microstructure with adequate strength and ductility during fabrication, and (4) preserve mechanical integrity and over-all dimensional accuracy, by minimizing the negative impact from irradiation such as void swelling, during the plant lifetime (Rowcliffe et al., 2018). The lower Cr content in the bainitic steels compared with RAFM steels can minimize the consumption of a strategic element (=chromium), which is another important factor, given the possible uncertainties of future chromium supplies (Klueh et al., 1997).