  A Kinetic Monte Carlo (KMC) model was created to simulate the insertion of
transmutation He atoms into nanostructured ferritic alloys (NFAs) under neutron
irradiation. Interstitial He atoms migrate through the NFA until becoming
trapped in bubbles of other He atoms and vacancies created from irradiation.
The Y-Ti-O nano-oxides in the NFAs were found to be effective in capturing
these He atoms and preventing bubbles from forming at the grain boundary and
appear to replicate the characteristics (size and number density) observed in
other experiments. The bubbles were found to prefer the <111> oxide interface
as a nucleation site and the stable bubbles have a He/Vac ratio between 1.3 and
1.8 He/Vac. The influence of He bubbles on the segregation of solutes to the
grain boundaries or on the stability of the nano-oxides were negligible.
