New Methodology for Small Boiling Water Reactor Stability Analysis (2024-2027)
This proposal aims to address the existing challenges associated with density wave oscillations (DWOs) in small modular boiling water reactors (SBWRs) operated under natural circulation for core cooling. DWOs driven by the kinetic wave propagation of vapor in boiling channels, can lead to instabilities and potential damage to the reactor fuel. The research team will leverage their expertise in BWR analysis and utilize TRACE/PARCS codes to simulate a BWRX-300-type reactor and define more precise instability boundaries that account for neutronic feedback mechanisms. The proposed work aims to enhance and innovate the criteria for defining safety stability regions in SBWRs and improve the understanding of DWOs (particularly during startup procedures), their underlying mechanisms, and potential mitigation strategies. The project’s specific objectives include analyzing the impact of DWOs on SBWR stability and reactor performance, developing a predictive model for identifying critical parameters that initiate and sustain DWOs, and providing recommendations for design verification and operational guidelines to enhance stability and safety.
PI: Juliana Pacheco Duarte
Co-PIs: Prof. Ben Lindley (UW-Madison) and Prof. Aaron Adams (Alabama A&M University)
Funding source: U.S. NRC
Using Machine Learning to Understand the Transient Critical Heat Flux and Post-CHF Heat Transfer (2023-2028)
To answer crucial questions on transient critical heat flux and post-CHF heat transfer behavior, the project plans to conduct experiments using high-resolution distributed temperature sensors in a directly heated fuel rod simulator at prototypical LWR accident conditions and use machine learning methods to improve the predictability capabilities of relevant computational codes. Two educational developments are proposed to promote broader and more inclusive nuclear engineering learning.
PI: Prof. Juliana P. Duarte
Funding source: NEUP Distinguished Early Career Program (DECP) Award
Non-dimensional Analysis of Density-Wave Instabilities and Dryout-Rewet Cycles during an ATWS (2021-2024)
This project aims to analyze the recent data collected in the Karlstein Thermal Hydraulic Test Facility (KATHY), in Germany, to develop a non-dimensional analysis that will demonstrate the general applicability of these test data in the study of Boiling Water Reactor Instabilities. The data were collected under conditions representative of an anticipated transient without scram (ATWS) at the Maximum Extended Load Line Limit Analysis Plus (MELLLA+). The analysis includes the development of criteria for the two-phase instability and for the failure to rewet events that can be applied to future system analysis under similar operating conditions. We also propose to investigate the transition boiling heat transfer coefficient from
the available data, and to assess TRACE/PARCS capability to simulate these instabilities. Finally, we will propose a scaling analysis based on a non-dimensional similarity group that can be used to design an experimental setup and verify the conclusions of this work. The results of this proposed work will address important gaps in the understanding of the two-phase flow instabilities that lead to dryout/rewet cycles and eventually to a fuel temperature excursion, which could damage the fuel rods.
PI: Prof. Juliana P. Duarte
Collaborators: Prof. Tomasz Kozlowski (UIUC), Prof. Michael Corradini (UW-Madison), and Prof. Yang Liu (VT)
Funding source: U.S. NRC
Journal and conference publications
- Hurley, P. Pigg, C., Liu, Y., Kozlowski, T., Duarte, J.P., “TRACE Assessment for Simulating Density Wave Oscillations in a Full-Scale BWR Rod Bundle Under Natural Circulation“, Nuclear Technology, 1-14, 2024. Conference publications
- Hurley, P., and Duarte, J.P., “A Comparison of Experimental Density Wave Instability Behavior with Analytical Model Prediction”, The 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20), Washington D.C., August 20–25, 2023.
- Hurley, P., and Duarte, J.P., “Prediction of Unstable Two-Phase Behavior using Dense Neural Network”, ANS Winter Meeting, Phoenix, AZ, November 12-17, 2022.
- Hurley, P., Liu, Y., Corradini, M., Kozlowski, T., Duarte, J., “Analysis of Flow Instability Onset in a BWR Rod Bundle Geometry,” Advances in Thermal Hydraulics (ATH 2022), Anaheim, CA, June 12-16, 2022. (Best Paper Award)
Thesis and dissertations
Paul Hurley, Dissertation: Density-Wave Instability Characterization in Boiling Water Reactors under MELLLA+ Domain during ATWS. Committee members: Prof. Juliana P. Duarte (chair), Prof. Yang Liu, Prof. John Palmore Jr, and Dr. Aaron Wysocki, University of Wisconsin Madison, Defense date: 03/20/2023.