b'Nuclear Science User Facilities Characterization and Modeling of Secondary PhaseEvolution in an Irradiated Zr-1.0Nb AlloyMatthew SwensonUniversity of Idahoswenson@uidaho.eduT he objective of this study is toResultscharacterize the evolution ofIn this study, atom-probe tomog-Nb-rich clustering and soluteraphy (APT) is used to systematically migration in a Zr-1.0%Nb alloyquantify the migration of Nb solutes irradiated with either neutrons or Kr2+due to each irradiation. Prior to irra-ions to otherwise similar conditionsdiation, only -Nb precipitates are (5 dpa at 310C), enabling isolationobserved, with a surrounding matrix of the dose-rate effects. Zirconium- containing 0.59 at% Nb, which is based alloys are commonly used asclose to the solubility limit for Nb cladding materials in existing reactor[1,2]. Following both irradiations, applications because of their lownanoscale Nb-rich clusters are found thermal-neutron absorption crosswithin the matrix, consistent with section, good corrosion resistance atprior observations [1,3,4], and are high temperature, and high resistancelikely elongated or needle-shaped, to irradiation-induced swelling andwith an average aspect ratio of ~2:1 creep. More recent development ofmeasured using APT. The irradiation-Zr-based alloys with small amountsinduced clustering coincides with of niobium has also demonstrateda reduction in matrix composition improvement in corrosion resistanceof Nb to 0.36 at% and 0.49 at% and the ability to minimize irradiation- following Kr2+ ion or neutron irra-induced linear growth. In this study, andiation, respectively. This evidence RXA Zr-1.0%Nb alloy was irradiatedsuggests the solutes migrate from with Kr2+ or neutrons to a commonthe matrix to irradiation-induced dose of ~5 dpa (each at 310C).clusters. The size of the Nb clusters Atom-probe tomography is used toare 4.51 1.09 nm and 4.17 2.23 quantify any solute-cluster morphologynm following Kr2+ and neutron and the solute concentrations in theirradiation, respectively, while matrix, clusters, and preexisting -Nbnumber density of the Nb clusters precipitates before and after eachare 3791021 m-3 and 2531021 irradiation. This approach enablesm-3 following the same irradiation systematic characterization of theconditions. Therefore, Kr2+ irradia-Nb-solute migration as a result oftions have resulted in higher volume irradiation, along with an evaluation offraction of Nb clustering at thedose rate effects and the ability for Kr2+same dose and temperature as ions to emulate neutron irradiation atneutron irradiation.low dose.64'