NSUF 19-1659: ChemiSTEM study of Nb redistribution in M5 irradiated at high burnup
We propose to study the Nb redistribution in terms of microstructure and microchemistry changes of a neutron irradiated M5® alloy to a burnup level of 63 to 70 GWd/MTU. The research objectives of this study are to provide knowledge on the Nb redistribution in term of forming Nb-rich rod-like precipitates at high burnup, how it is comparable to its redistribution under proton irradiation (already performed by the research team, see previous NSUF publications) and how the Nb is then redistributed in the protective oxide layer. The underlying hypothesis is that the distribution of Nb in the growing oxide, inherited from its redistribution in the irradiated metal microstructure, is responsible for the low corrosion rates experienced by Nb containing fuel cladding alloys in reactor.The purpose of this RTE is to characterize the neutron irradiated M5® with a focus on the oxide region. Three TEM lamellas will be prepared using the FEI Quanta 3D 200i Dual Beam (FIB) at LAMBDA, one in the bulk, one at the oxide/metal interface and one further into the protective oxide. Then, the irradiation induced Nb-rich rod-like precipitates will be characterized (densities, compositions and sizes) under high resolution STEM mode using the Talos F200X STEM microscope at LAMBDA. It is well known that native βNb precipitates experience delayed oxidation in the zirconium oxide matrix, however the fate of the irradiation induced Nb-rich rod-like precipitates in the oxide is relatively unknown, although they are, to some extent, controlling the corrosion kinetics. Thus, a comparison between the 3 lamellas will shed light on the oxidation of these radiation induced precipitates and their densities in the oxide, compared to the bulk.This Nb solute concentration, known to control the corrosion kinetics, is suspected to be lowered by the radiation-induced precipitation of Nb rich needle like precipitates. This decrease of Nb in solid solution under irradiation is hypothesized to be primarily responsible for the relatively low in-reactor corrosion kinetics experienced by ZrNb alloys even at large burnups (up to 80 GWd/MTU), at the contrary to Zircaloys, which experience an increase in corrosion kinetics at relatively high burnup (~50 GWd/MTU). This overall hypothesis is tested through an on-going research program that has completed multiple RTEs on proton irradiated samples. Thus the characterization of neutron irradiated materials is a natural evolution of the project and results will be compared to the wealth of data acquired on proton irradiated materials. Besides the fundamental understanding of fuel cladding corrosion, this research contributes to current fuel cladding design in order to maximize safety and burnup for use in current generation of nuclear reactors. This RTE will also inform the on-going effort to evaluate the potential for proton irradiation to mimic neutron irradiation for fuel cladding licensing purposes.
Additional Info
| Field | Value |
|---|---|
| Abstract | We propose to study the Nb redistribution in terms of microstructure and microchemistry changes of a neutron irradiated M5® alloy to a burnup level of 63 to 70 GWd/MTU. The research objectives of this study are to provide knowledge on the Nb redistribution in term of forming Nb-rich rod-like precipitates at high burnup, how it is comparable to its redistribution under proton irradiation (already performed by the research team, see previous NSUF publications) and how the Nb is then redistributed in the protective oxide layer. The underlying hypothesis is that the distribution of Nb in the growing oxide, inherited from its redistribution in the irradiated metal microstructure, is responsible for the low corrosion rates experienced by Nb containing fuel cladding alloys in reactor.The purpose of this RTE is to characterize the neutron irradiated M5® with a focus on the oxide region. Three TEM lamellas will be prepared using the FEI Quanta 3D 200i Dual Beam (FIB) at LAMBDA, one in the bulk, one at the oxide/metal interface and one further into the protective oxide. Then, the irradiation induced Nb-rich rod-like precipitates will be characterized (densities, compositions and sizes) under high resolution STEM mode using the Talos F200X STEM microscope at LAMBDA. It is well known that native βNb precipitates experience delayed oxidation in the zirconium oxide matrix, however the fate of the irradiation induced Nb-rich rod-like precipitates in the oxide is relatively unknown, although they are, to some extent, controlling the corrosion kinetics. Thus, a comparison between the 3 lamellas will shed light on the oxidation of these radiation induced precipitates and their densities in the oxide, compared to the bulk.This Nb solute concentration, known to control the corrosion kinetics, is suspected to be lowered by the radiation-induced precipitation of Nb rich needle like precipitates. This decrease of Nb in solid solution under irradiation is hypothesized to be primarily responsible for the relatively low in-reactor corrosion kinetics experienced by ZrNb alloys even at large burnups (up to 80 GWd/MTU), at the contrary to Zircaloys, which experience an increase in corrosion kinetics at relatively high burnup (~50 GWd/MTU). This overall hypothesis is tested through an on-going research program that has completed multiple RTEs on proton irradiated samples. Thus the characterization of neutron irradiated materials is a natural evolution of the project and results will be compared to the wealth of data acquired on proton irradiated materials. Besides the fundamental understanding of fuel cladding corrosion, this research contributes to current fuel cladding design in order to maximize safety and burnup for use in current generation of nuclear reactors. This RTE will also inform the on-going effort to evaluate the potential for proton irradiation to mimic neutron irradiation for fuel cladding licensing purposes. |
| Award Announced Date | 2019-02-08T00:00:00 |
| Awarded Institution | Center for Advanced Energy Studies |
| Facility | Microscopy and Characterization Suite |
| Facility Tech Lead | Kory Linton, Yaqiao Wu |
| Irradiation Facility | None |
| PI | Adrien Couet |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1659 |