Ferritic/Martensitic (F/M) steels with high Cr content posses the high temperature strength and low
swelling rates required for advanced nuclear reactor designs. Radiation induced segregation (RIS) occurs
in F/M steels due to solute atoms preferentially coupling to point defect fluxes which migrate to defect
sinks, such as grain boundaries (GBs). The RIS response of F/M steels and austenitic steels has been shown
to be dependent on the local structure of GBs where low energy structures have suppressed RIS
responses. This relationship between local GB structure and RIS has been demonstrated primarily in
ion-irradiated specimens. A 9 wt.% Cr model alloy steel was irradiated to 3 dpa using neutrons at the
Advanced Test Reactor (ATR) to determine the effect of a neutron radiation environment on the RIS
response at different GB structures. This investigation found the relationship between GB structure
and RIS is also active for F/M steels irradiated using neutrons. The data generated from the neutron irradiation
is also compared to RIS data generated using proton irradiations on the same heat of model alloy.
