Atom probe tomography of Zircaloy-2 exposed to boiling water reactor operation
Licentiatavhandling, 2021

Zirconium alloys are used as cladding tubes for the fuel in nuclear reactors. In boiling water reactors (BWRs), the alloy Zircaloy-2, which contains the alloying elements Sn, Fe, Cr, Ni, and O, is commonly used. In this thesis, results from atom probe tomography studies of Zircaloy-2 exposed to three and nine annual cycles of BWR operation are presented. The alloying elements were observed to be redistributed after reactor exposure. Clusters of Fe and Cr or Fe and Ni were observed at expected positions of radiation-induced <a> type dislocation loops. Regions containing mainly Fe–Cr clusters were much more common than regions containing mainly Fe–Ni clusters. The Fe–Cr clusters appeared dense and spheroidal, whereas the Fe–Ni clusters appeared dilute and disc-shaped. The Fe–Ni discs occupied planes that correspond to all three families of first-order prismatic planes but with deviation from perfect <c> axis alignment. Many grain boundaries were observed, and there were large grain-to-grain variations in cluster number density and cluster composition. Regarding cluster number density, there was on average no difference between three cycles and nine cycles. After nine cycles the clusters were on average larger and contained more Cr. Sn was observed to cluster in regions where there were no Fe–Cr or Fe–Ni clusters. Enrichment of Sn and Fe and small amounts of Cr and Ni was observed at grain boundaries. After nine cycles, but not after three cycles, enrichment of Sn, Fe, and Ni at ring-shaped features interpreted to be radiation-induced <c> component loops was observed. Hydrogen was observed to be preferentially located outside a partially dissolved Zr(Fe,Cr)2 second phase particle that also contained Ni and Si. The present work demonstrates that the well-known dislocation loops have a chemistry, in the form of clusters of different types and shapes, that might substantially affect mechanisms degrading the cladding tubes, e.g. irradiation growth, corrosion, and hydrogen pickup.

Nuclear fuel claddings

Zirconium alloys

Boiling water reactor

Clustering

Atom probe tomography

Radiation effects

Zircaloy-2

Dislocation loops

PJ-salen
Opponent: Christina Bjerkén, Malmö universitet, Sverige

Författare

Johan Eriksson

Chalmers, Fysik, Mikrostrukturfysik

Eriksson, J., Sundell G., Tejland, P., Andrén H.-O., Thuvander, M. Nanoscale chemistry of Zircaloy-2 exposed to three and nine annual cycles of boiling water reactor operation — an atom probe tomography study

Styrkeområden

Energi

Materialvetenskap

Ämneskategorier

Materialkemi

Annan materialteknik

Metallurgi och metalliska material

Korrosionsteknik

Infrastruktur

Chalmers materialanalyslaboratorium

Utgivare

Chalmers tekniska högskola

PJ-salen

Opponent: Christina Bjerkén, Malmö universitet, Sverige

Mer information

Senast uppdaterat

2021-04-21