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oxides are the major features that provide high strength and irradiation tolerance in nano-structured ferritic alloys. Here, we employ density functional theory to study helium trapping in Y 2 TiO 5 . The results suggest that helium is more deeply trapped in Y 2 TiO 5 compared to Y 2 Ti 2 O 7 . Helium occupies open channels in Y 2 TiO 5 , where it weakly chemically interacts with neighboring oxygen anions, and results in less volume expansion compared to Y 2 Ti 2 O 7 , reducing strains in the iron matrix. The corresponding helium mobility in these channels is very high. While its ultimate fate is to form oxide/matrix interface bubbles, transient deep trapping of helium in oxides plays a major role in the ability of NFA to manage helium distribution.