An atom probe tomography study of the chemistry of radiation-induced dislocation loops in Zircaloy-2 exposed to boiling water reactor operation

This study is complementary to previous atom probe tomography (APT) studies of irradiation effects in the zirconium alloy Zircaloy-2. Using APT in voltage pulse mode, a difference in morphology was ob-served between clusters of Fe and Ni and clusters of Fe and Cr in Zircaloy-2 exposed to a high fast neutron fluence in a commercial boiling water reactor. The Fe-Ni clusters were disc-shaped with a di-ameter of 5-15 nm, whereas the Fe-Cr clusters were spheroidal with a diameter of approximately 5 nm. Both types of clusters appeared to be located at irradiation-induced < a >-type dislocation loops aligned in layers normal to the < c > -direction. The concentration of Fe was higher in the Fe-Cr clusters than in the Fe-Ni clusters. The dilute Fe-Ni clusters, which seem to be segregation of Fe and Ni inside the loops, had formed on all three families of first-order prismatic planes with some deviation from perfect < c > -axis alignment. The Fe-Cr clusters might be very small precipitates with a nucleation associated with the loops. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )