On the potential synergies of helium and hydrogen on the nucleation and stability of cavity clusters in Inconel X-750^® irradiated in a high thermal neutron flux spectra

The degradation of structural materials as a result of helium and hydrogen generated through nuclear transmutation is now well documented; however, not fully understood. The amount of these elements produced can be accurately estimated if the neutron energy spectrum in the irradiation environment is well known. Our experimental measurements have confirmed the full retention of helium, and up to approximately 40% of the hydrogen produced by transmutation. Atomistic modeling suggest that bubbles formed during irradiation have a high density helium core, surrounded by a hydrogen-enriched metal matrix interface. High resolution electron energy loss spectroscopy has been performed and supports the atomistic modeling conclusions by illustrating the hydrogen signal as a halo surrounding helium bubbles. Material has been characterized with doses up to 80 dpa with up to 25000 appm retained helium and ~2000 appm retained hydrogen. This paper will use these experimental results to gain an improved understanding of the effects of irradiation on the structural integrity of austenitic materials following irradiation in a high thermal neutron flux spectra.