Progress in Suppressing Hydrogen Isotopes Retention in Fusion Reactor Material

Reduced activation ferritic/martensitic (RAFM) steel is the first-choice structural material for fusion reactors’ internal components. In fusion reactors, tritium may penetrate through the first wall of internal components into coolant and lead to loss of tritium. In view of the very high value of tritium and the harm of radioactive coolant, e.g. tritiated water, plasma interactions with RAFM steel is an important issue concerning economy and safety of fusion reactor. 

Plasma interactions with RAFM steel have been extensively investigated for the potential use of RAFM steel as structural material in fusion reactors. When fusion reaction takes place, Helium (He) will be continuously produced and has significant effect on H behavior in the material. Previous research works have made two opposite conclusions. Some report that He has two contrary effects on the H isotope retention, i.e. some data suggested that He pre-irradiation can enhance H retention in the following H exposures, whereas the others suggested an opposite trend. 

An ASIPP research group led by Dr. Hai-Shan Zhou has been studying on the suppressing of hydrogen isotopes retention in RAFM steel. Recently, they found that the deeply pre-injected He can reduce H bulk trapping, whereas the surface damage induced by He significantly increase H retention. 

To clarify the two possible effects on H retention, the group performed a series of experiments. He-damaged layers at the surface and inside the RAFM bulk are induced by 3.5 MeV He ion bombardments with and without energy degrader, respectively. Iron (Fe) ionpre-irradiation is performed as a comparison so that He effects are clearly distinguished. (LIU Haodong reports) 

The above research has been published by Nuclear Fusion (Nucl. Fusion 58 (2018) 056017). 

Link to article：https://doi.org/10.1088/1741-4326/aab37e 

He and irradiation damage distribution for 3.5 MeV He ion into RAFM steel 

TEM images for 3.5 MeV He ion pre-damaged RAFM steel

D thermal desorption spectroscopy measurements after plasma exposures 

(Fe ion experiments for comparison)