Development of next generation tempered and ODS reduced activation ferritic/martensitic steels for fusion energy applications

Abstract

Reduced activation ferritic/martensitic steels are currently the most technologically mature option for the structural material of proposed fusion energy reactors. Advanced nextgeneration higher performance steels offer the opportunity for improvements in fusion reactor operational lifetime and reliability, superior neutron radiation damage resistance, higher thermodynamic efficiency, and reduced construction costs. The two main strategies for developing improved steels for fusion energy applications are based on (1) an evolutionary pathway using computational thermodynamics modelling and modified thermomechanical treatments (TMT) to produce higher performance reduced activation ferritic/martensitic (RAFM) steels and (2) a higher risk, potentially higher payoff approach based on powder metallurgy techniques to produce very high strength oxide dispersion strengthened (ODS) steels capable of operation to very high temperatures and with potentially very high resistance to fusion neutron-induced property degradation. The current development status of these nextgeneration high performance steels is summarized, and research and development challenges for the successful development of these materials are outlined. Material properties including temperature-dependent uniaxial yield strengths, tensile elongations, high-temperature thermal creep, Charpy impact ductile to brittle transient temperature (DBTT) and fracture toughness behaviour, and neutron irradiation-induced low-temperature hardening and embrittlement and intermediate-temperature volumetric void swelling (including effects associated with fusionrelevant helium and hydrogen generation) are described for research heats of the new steels.

Characterization of polyhedral nano-oxides and helium bubbles in an annealed nanostructured ferritic alloy

“…Nanostructured ferritic alloys (NFAs) are a revolutionary class of Fe-Cr-based oxide dispersion strengthened (ODS) steels with many outstanding mechanical, thermal, and chemical properties for nuclear applications [1][2][3][4][5][6][7][8][9][10] . NFAs have high temperature strength and stability up to 900 °C [11 , 12] and unmatched radiation resistance, especially with respect to managing helium generated by nuclear transmutation reactions [1 , 13-18] .…”

Microstructure Characterization and Mechanical Properties of Al Alloyed 9Cr ODS Steels with Different Al Contents

“…No martensite was found in 2.5Al‐ODS and 4.5Al‐ODS steels, which is also accordance with the phase diagram calculation as shown in Figure . For the low Cr ODS steels, high temperature phase stability is a factor to limit the service temperature, the addition of Al may a solution way for this problem.…”

“…Ferritic/martensitic oxide dispersion strengthened (ODS) steels are considered as promising materials for core application in generation‐IV fission and fusion reactors because of their excellent irradiation resistance and high temperature mechanical properties . Concentrations around 8–9 wt% Cr are considered as the best compromise between different properties for nuclear application .…”

A new method for improving the tritium breeding and releasing performance of China Fusion Engineering Test Reactor phase II helium‐cooled ceramic breeder blanket

“…The details are as follows: The protective coat for FW still adopts the tungsten armor of 2 mm 9,13 The structural material updates from the traditional Reduced Activation Ferritic/Martensitic (RAFM) steel to the oxide dispersion strengthened RAFM steel 21,22,26,27 . The temperature limit of the new steel increases from the previous 550°C to 650°C through adding dispersion oxide, while the material properties almost keep unchanged.…”