NSUF 25-5398: Quantifying Recovery and Recrystallization Kinetics of Irradiated Zircaloy-4 Cladding During Time-at-Temperature Transients
To meet growing energy demands, the existing nuclear reactor fleet must enhance safety and economic efficiencies through a better understanding of core materials during operationally limiting accident transients. Transient temperature excursions can be classified by frequency and severity: (1) severe accidents like Fukushima (10^-2 per reactor-year) that can cause rapid temperature spikes. Examples of AOOs include turbine trip and feedwater controller failures, which can cause temperature spikes to ~750 °C for seconds before reverting to the ~300 °C operational temperature. Current regulations limit these temperature excursions to prevent boiling transitions, which necessitate shutdowns and removal of fuel rods, thus restricting core design and decreasing fuel cycle efficiency. To optimize reactor performance, a shift from a strict thermal-hydraulic focus to a material-specific integrity criterion based on “time-at-temperature” (t@T) during AOOs is crucial. A material-based limit for fuel cladding could enhance operational margins, reduce downtime, and improve safety by minimizing operator radiation exposure. Recent studies on un-irradiated zirconium cladding have suggested that temperature excursions affect mechanical behavior due to recrystallization, although detailed mechanistic understanding is limited from ex-situ testing. This proposal intends to use in-situ synchrotron X-Ray diffraction at the Advanced Photon Source (APS) to investigate microstructural changes in zirconium-based fuel cladding during temperature transients. Analyzing dislocation density, grain size, and texture will provide insights into microstructural evolution under relevant t@T conditions. These findings could inform future regulatory practices, revising integrity criteria to allow brief exposures in post-CHF scenarios, enhancing operational margins and improving plant flexibility and fuel cycle economics.
Additional Info
| Field | Value |
|---|---|
| Awarded Institution | Oak Ridge National Laboratory |
| DOI | 10.46936/NSUF/60015376 |
| Embargo End Date | 2027-09-03 |
| Facility Tech Lead | Kory Linton, Wei-Ying Chen |
| NSUF Call | FY 2025 RTE 2nd Call |
| PI | Sam Bell |
| PIE Facilities | Activated Materials Laboratory-Advanced Photon Source (1-ID, 20-ID beamlines) |
| Prep Facilities | Irradiated Materials Examination and Testing Facility, Irradiated Materials Laboratory |
| Project Member | Dr. Caleb Massey, R&D Staff Member - Oak Ridge National Laboratory (https://orcid.org/0000-0003-1093-3958) |
| Project Member | Dr. Lin Gao, Assistant Professor - University of Alabama (https://orcid.org/0000-0001-8988-7354) |
| Project Member | Dr. Sam Bell, Research Associate - Oak Ridge National Laboratory (https://orcid.org/0000-0002-5190-5657) |
| Project Type | RTE |