Materials Genomics Search for Possible Helium-Absorbing Nano-Phases in Fusion Structural Materials

Civilian fusion demands structural materials that can withstand the harsh environments in fusion plasma reactors. The structural materials often transmute under 14.1 MeV fast neutrons, producing helium (He), which embrittles the grain boundary (GB) network. Adding load-bearing second-phase nanoparticles (0D) or nanowires (1D) with atomic-scale free volume and low He-embedding energy <i>E</i>_emb as volumetric He sinks may shield the 2D GBs from He segregation and combat He embrittlement; however, the ability to disperse low-<i>E</i>_emb nano-phases to screen GB from Helium embrittlement has not been fully unlocked yet due to the lack of material selection guidelines. Here we show that neutron-friendly and mechanically strong nano-phases with atomic-scale free volume can have low <i>E</i>_emb and &gt;10 at% He-absorbing capacity, and could thus be exceptionally advantageous for soaking up He on top of resisting radiation damage and creep, provided they have thermodynamic compatibility and wettability with the matrix as well as high enough melting point. Our preliminary experimental demonstration proves that He-embedding energy is a good <i>ab initio</i> predictor of He shielding tendencies in hetero-phase materials, and can be used for computational screening. In this context, we present a list of compounds expected to be good He-absorbing nano-phases, taking into account <i>E</i>_emb, the neutron absorption, and activation cross-sections, the melting temperature, the thermodynamic compatibility, and the wetting angle of the nano-phases with the Fe matrix as an example.