Critical Assessment 12: Prospects for reduced activation steel for fusion plant

Abstract

The development of new, high performance reduced activation materials is increasingly recognised as one of the key enabling technologies required for the advancement of civil fusion power. Reduced activation steels are considered the leading materials for fusion reactor blanket structural materials. The manufacturing technologies and database for the current leading reduced activation steels have reached a state of maturity where basic design and implementation can be addressed. However, there remain concerns with these materials due to an incomplete irradiation database and because of their limited operational temperature window. The requirements of these steels along with various proposed methods to improve reduced activation steels are critically assessed, and some indications given on future paths for progress.

Short communication: ‘Low activation, refractory, high entropy alloys for nuclear applications’

“…However, as pointed out in [19], the suitability of these alloys for use in the next generation of advanced nuclear reactors is somewhat restricted by the high activation elements Nb and Mo. Although activation issues are significantly reduced compared to the most common cobalt containing FCC HEAs, these high activation elements require substantially longer time periods before the radioactivity levels reach a satisfactory limit for 'hands on' maintenance [30]. Materials based on low activation elements, with minimal impurities, have a profound environmental impact by reducing the quantity of high level radioactive waste during decommissioning and allow in-core components to be recycled; low activation is also an essential design criteria for fusion reactors [31,32].…”

Impact of friction stir welding on the microstructure of ODS steel

“…The specimens prepared for optical microscopy were finally etched with a solution containing 15 vol.% HCl and 3 vol.% HNO 3 . Optical micrographs of the weld cross sections were taken using a Keyence VK-X200K 3D laser scanning microscope, whereas micrographs of the particles present at the weld border were taken on a Struers DuraScan automatic hardness tester.…”

“…Oxide dispersion-strengthened (ODS) steels are currently considered as leading candidate materials for the production of thin-wall cladding tubes for Gen IV fast nuclear reactors, and also for first-wall components in magnetically-confined fusion reactors [1][2][3]. Their attractiveness as structural materials for future nuclear energy systems lies in their enhanced high-temperature strength and creep resistance, which allows to extend the high-temperature safe limit of reactor operation beyond the value of ∼600°C characteristic of ferritic/martensitic steels [4], coupled to their high resistance to the expected neutron doses potentially beyond 100 dpa [5,6].…”

An analysis of the microstructure of spark plasma sintered and hot isostatically pressed V 4Cr 4Ti 1.8Y 0.4Ti3SiC2 alloy and its thermal stability

“…The blanket has multiple roles and requirements: a) convert the kinetic energy of neutrons into heat, b) extract the heat to generate power, c) produce tritium to continue the fusion reaction, and d) maintain structural integrity for at least 5 years [1]. Currently, there are no commercially available materials capable of satisfying all of these requirements and thus there is a significant technological barrier for incorporation of fusion into our energy supply systems [2].…”

“…Ferritic/martensitic steels are currently the most feasible choice owing to substantial levels of development work as well significant industrial experience with such alloys in the fossil fuel and nuclear fission sectors [2e5]. A key problem with current RAFM steels such as Eurofer 97 and F82H, however, is that the temperature operating window within the anticipated conditions of the first wall/blanket is limited to approximately 350e550 C; below 350 C the material becomes brittle because of neutron damage and above 550 C the creep rates become unacceptably high [2]. Alternatively, ODS steels have the potential to increase the maximum operating temperature by several hundred degrees because of the incorporation of a fine dispersion of 2e5 nm diameter, thermodynamically stable Y, Ti and O-rich precipitates, which are uniformly distributed throughout a ferrite matrix [3,6].…”