NSUF 17-1001: APT and TEM study of redistribution of alloying elements in ZrNb alloys following proton irradiation: effects on in-reactor corrosion kinetics.
We propose to study the effect of proton irradiation on Nb redistribution into the ZrNb alloy matrix. The research objectives of this study are to provide knowledge on the Nb redistribution upon proton irradiation, how it is comparable to its redistribution under neutron irradiation and how it affects the ZrNb alloys in-reactor corrosion kinetics. This study aims at precisely characterizing the microstructure and microchemistry at the nanoscale of proton irradiated ZrNb alloys with different Nb contents, below and above the theoretical solid solubility limit. As part of the RTE, this study will utilize the Focused Ion Beam technique to prepare TEM lamellae by lift-out techniques and APT needles from the irradiated specimen. The samples are Zr-xNb binary model alloys (x=0.2-0.4-0.5-1.0wt%) all irradiated up to 1 dpa. TEM examinations of the lamellae will focus on characterizing the microstructure and microchemistry of the concentrated Nb phases (ßNb native precipitates and irradiation induced needle like precipitates). The microstructure of the native precipitates will be characterized by XRD while ASTAR will be primarily used to obtained the orientation distribution of the small needle like precipitates formed under irradiation. The precipitate chemistry will be examined by EDS. The density of the different precipitates as well as their Nb content will be particularly examined and determined from large STEM maps covering multiple grains. In addition, after characterization, the sample will be heated up to 350°C using the Hummingbird heating stage to determine if the needle like precipitates are stable at reactor temperatures while the sample is not subjected to irradiation. The FIB needles will be examined by APT to reveal the concentration of Nb in solid solution. Indeed, this 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 large research program in which the present RTE would bring critical data to its success. This information will allow for the contribution to and re-evaluation of 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 effect of proton irradiation on Nb redistribution into the ZrNb alloy matrix. The research objectives of this study are to provide knowledge on the Nb redistribution upon proton irradiation, how it is comparable to its redistribution under neutron irradiation and how it affects the ZrNb alloys in-reactor corrosion kinetics. This study aims at precisely characterizing the microstructure and microchemistry at the nanoscale of proton irradiated ZrNb alloys with different Nb contents, below and above the theoretical solid solubility limit. As part of the RTE, this study will utilize the Focused Ion Beam technique to prepare TEM lamellae by lift-out techniques and APT needles from the irradiated specimen. The samples are Zr-xNb binary model alloys (x=0.2-0.4-0.5-1.0wt%) all irradiated up to 1 dpa. TEM examinations of the lamellae will focus on characterizing the microstructure and microchemistry of the concentrated Nb phases (ßNb native precipitates and irradiation induced needle like precipitates). The microstructure of the native precipitates will be characterized by XRD while ASTAR will be primarily used to obtained the orientation distribution of the small needle like precipitates formed under irradiation. The precipitate chemistry will be examined by EDS. The density of the different precipitates as well as their Nb content will be particularly examined and determined from large STEM maps covering multiple grains. In addition, after characterization, the sample will be heated up to 350°C using the Hummingbird heating stage to determine if the needle like precipitates are stable at reactor temperatures while the sample is not subjected to irradiation. The FIB needles will be examined by APT to reveal the concentration of Nb in solid solution. Indeed, this 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 large research program in which the present RTE would bring critical data to its success. This information will allow for the contribution to and re-evaluation of 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 | 2017-09-20T12:29:31.71 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Yaqiao Wu |
| Irradiation Facility | None |
| PI | Adrien Couet |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1001 |