NSUF 17-1093: AsTeROID (follow-on AsTeR (Advanced Test Reactor) project to Optimize hydrogen-assisted Irradiation growth and Dimensional stability)
The scientific objective of this project is to develop a better understanding of the mechanisms in the hydrogen-assisted irradiation growth phenomena via thermal annealing using dilatometry, differential scanning calorimetry (DSC), and hot-stage transmission electron microscopy (TEM). We hypothesize that these techniques can measure significant changes on existing irradiated Zircaloy-4 AsTeR specimens during annealing.
Irradiation growth in nuclear fuel affects the dimensional stability of fuel assemblies that can lead to operational and safety issues such as BWR channel distortion and PWR fuel assembly distortion both of which may impede control rod movement, cause thermal hydraulic and neutronic penalties that limit cost-efficient fuel utilization, and cause fuel handling issues due to distorted fuel assemblies. Additionally, hydrogen pickup (HPU) in zirconium-based alloys due to corrosion of the zirconium has been found to enhance irradiation growth in an alloy-specific manner.
Developing a better understanding of the thermal recovery mechanisms of irradiation damage and growth will lead to the development of a mechanistic understanding of the hydrogen-assisted growth of zirconium alloys. There is a correlation between the initiation of c-loops and the beginning of breakaway growth. The key to understanding high fluence growth and the influence of hydrogen on not just increasing growth but also in decreasing the fluence to breakaway, is to understand the interaction of hydrogen with c-loops and line dislocations
Irradiation-induced c-loops in zirconium alloys are thermally stable up to high temperatures and their contribution to recovery of irradiation growth is not well known. In addition, the effect of hydrogen content (in solution and in the form of hydrides) of zirconium alloys on irradiation growth is not fully established. Although progress has been made in this area, much work needs to be done to develop a usable model of hydrogen assisted growth.
We propose to help close this gap by investigating the relationship between microstructural changes and irradiation growth of zirconium alloys through post-irradiation annealing. The phenomenon of thermal recovery, proposed here, will provide R&D results complementary to ongoing EPRI projects (DS and AsTeR) by examining the individual contributions of a-and c-loops on pre-breakaway irradiation growth and the effect of microstructural changes that occur during annealing on hardness and other mechanical properties.
The scope of this work consists of TEM with hot stage, DSC and dilatometry. The experiments will be performed on eight Zircaloy-4 samples that were irradiated in the ATR to different neutron damage levels during the AsTeR Project. The irradiation growth and TEM characterization data for these zirconium-based alloys emerging from the AsTeR Project will be used as a reference point. These alloys will be annealed under inert atmosphere for 1 to 3 hours followed by length and enthalpy measurements or TEM examination to provide c-and a-loop densities.
The project can be initiated upon award and is expected to take a maximum of 9 months to complete.
Additionally, the AsTeR Project samples included under this proposal will be offered to the NSUF Sample Library for use by other researchers.
Additional Info
| Field | Value |
|---|---|
| Abstract | The scientific objective of this project is to develop a better understanding of the mechanisms in the hydrogen-assisted irradiation growth phenomena via thermal annealing using dilatometry, differential scanning calorimetry (DSC), and hot-stage transmission electron microscopy (TEM). We hypothesize that these techniques can measure significant changes on existing irradiated Zircaloy-4 AsTeR specimens during annealing. Irradiation growth in nuclear fuel affects the dimensional stability of fuel assemblies that can lead to operational and safety issues such as BWR channel distortion and PWR fuel assembly distortion both of which may impede control rod movement, cause thermal hydraulic and neutronic penalties that limit cost-efficient fuel utilization, and cause fuel handling issues due to distorted fuel assemblies. Additionally, hydrogen pickup (HPU) in zirconium-based alloys due to corrosion of the zirconium has been found to enhance irradiation growth in an alloy-specific manner. Developing a better understanding of the thermal recovery mechanisms of irradiation damage and growth will lead to the development of a mechanistic understanding of the hydrogen-assisted growth of zirconium alloys. There is a correlation between the initiation of c-loops and the beginning of breakaway growth. The key to understanding high fluence growth and the influence of hydrogen on not just increasing growth but also in decreasing the fluence to breakaway, is to understand the interaction of hydrogen with c-loops and line dislocations Irradiation-induced c-loops in zirconium alloys are thermally stable up to high temperatures and their contribution to recovery of irradiation growth is not well known. In addition, the effect of hydrogen content (in solution and in the form of hydrides) of zirconium alloys on irradiation growth is not fully established. Although progress has been made in this area, much work needs to be done to develop a usable model of hydrogen assisted growth. We propose to help close this gap by investigating the relationship between microstructural changes and irradiation growth of zirconium alloys through post-irradiation annealing. The phenomenon of thermal recovery, proposed here, will provide R&D results complementary to ongoing EPRI projects (DS and AsTeR) by examining the individual contributions of a-and c-loops on pre-breakaway irradiation growth and the effect of microstructural changes that occur during annealing on hardness and other mechanical properties. The scope of this work consists of TEM with hot stage, DSC and dilatometry. The experiments will be performed on eight Zircaloy-4 samples that were irradiated in the ATR to different neutron damage levels during the AsTeR Project. The irradiation growth and TEM characterization data for these zirconium-based alloys emerging from the AsTeR Project will be used as a reference point. These alloys will be annealed under inert atmosphere for 1 to 3 hours followed by length and enthalpy measurements or TEM examination to provide c-and a-loop densities. The project can be initiated upon award and is expected to take a maximum of 9 months to complete. Additionally, the AsTeR Project samples included under this proposal will be offered to the NSUF Sample Library for use by other researchers. |
| Award Announced Date | 2017-09-20T12:36:25.57 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Alina Zackrone |
| Irradiation Facility | None |
| PI | Erik Mader |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1093 |