SYMPOSIA PAPER Published: 28 July 2021
STP162220190052

Toward an Improved Understanding of the Mechanisms Involved in the Increased Hydrogen Uptake and Corrosion at High Burnups in Zirconium Based Claddings

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In reactor environment, under irradiation, the corrosion and hydrogen uptake do not follow the rules valid for autoclave conditions. After sufficient study, it has been demonstrated that these two phenomena are different in reactor and not only the rate of corrosion but also that of hydrogen uptake change. In many alloys, they increase at high burnups. The causes of this change in behavior with irradiation are still debated. Although most aspects of this topic are examined, the full picture is not yet portrayed. In the frame of a project running at PSI, different alloys irradiated in two types of reactors are analyzed to correlate the characterization to the change of behavior. The metal-oxide microstructure has been examined by analytical techniques such as electron probe microanalysis, three-dimensional focused ion beam and transmission electron microscopy. The mechanical properties of the oxide in the vicinity of the metal-oxide interface as well as its semiconducting properties are explored at a microscopic level. In order to see the evolution of the aforementioned properties, a high-burnup sample is compared with the low-burnup material of the same cladding. The evolution of the aforementioned properties is considered to determine the different factors at the origin of the modified hydrogen pickup fraction at high burnup. Other alloys are then examined searching for similar behaviors. From these measurements, it can be concluded that not a single mechanism is involved in the process of oxidation and hydrogen uptake. In particular, as the residence time increases, different modifications and their mechanisms run in parallel. It is demonstrated that the “multilayer” formed from metal and oxide, responsible for the protection of the cladding against the ingress of different species, becomes more porous and less conducting in the oxide, but also its mechanical strength is modified. These progressive changes lead to different schemes for corrosion and hydrogen uptake.

Author Information

Abolhassani, Sousan
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Baris, Adrienn
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Grabherr, Robin
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Hawes, Jonathan
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Colldeweih, Aaron
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Vanta, Radovan
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Restani, Renato
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Hermann, Armin
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Bertsch, Johannes
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Chollet, Melanie
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Kuri, Goutam
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Martin, Matthias
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Portier, Stephane
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Wiese, Holger
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Schweikert, Herbert
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Bart, Gerhard
Laboratory for Nuclear Materials (NES), and AHL (NES), Paul Scherrer Institut, CH
Ammon, Katja
Kernkraftwerk Leibstadt AG, CH
Ledergerber, Guido
Kernkraftwerk Leibstadt AG, CH
Limbäck, Magnus
Westinghouse Electric Sweden AB, Fuel Materials Center of Excellence, SE
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Pages: 435–466
DOI: 10.1520/STP162220190052
ISBN-EB: 978-0-8031-7691-1
ISBN-13: 978-0-8031-7690-4