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Q&A with Brian Wirth

Brian Wirth is an Oak Ridge National Laboratory-University of Tennessee Governor’s Chair for computational nuclear engineering.
OAK RIDGE, Tenn., Sep. 29, 2011 — Brian Wirth is an Oak Ridge National Laboratory-University of Tennessee Governor's Chair for computational nuclear engineering. He is the co-editor, along with Kurt Edsinger of the Electric Power Research Institute and Chris Stanek of Los Alamos National Laboratory, of a special issue of the Journal of Metals on computational modeling of nuclear fuel performance. Wirth, Edsinger and Stanek also author two articles in the edition.

What is CASL, and how is it designed to address fuel-related challenges in the nuclear industry?

Wirth: CASL is the Consortium for the Advanced Simulation of Light Water Reactors, and is a Department of Energy Modeling & Simulation Hub that has the objective of predicting nuclear reactor performance. This will enable us to have a better understanding of the safety margins during normal power plant operation and therefore provide the basis for power uprates and lifetime extensions.

What is the leading fuel failure mechanism in nuclear reactors?

Wirth: By far the leading fuel failure mechanism relates to grid-to-rod fretting, wherein a gap develops between the springs of the spacer grids and the fuel rod itself as a consequence of operating exposure. The very high velocity of the coolant induces rod vibrations that repeatedly bring the fuel rod into contact with the spacer grid. Over time, this induces wear damage that can completely penetrate the fuel clad, leading to the release of radioactive fission products into the coolant.

How can high-performance computing help improve nuclear fuel performance?

Wirth: We have reached a stage with high-performance computing where we can begin to couple models of very complicated processes with high physical fidelity to predict performance. In the case of grid-to-rod fretting, this requires coupling the underlying materials microstructure processes leading to the development of a gap between the spacer grid and fuel rod with computational fluid mechanics to better predict the fluid structure interaction. This will help us to understand the turbulent forces causing rod vibration.

How is CASL interfacing with industry to enable improvements in existing reactors?

Wirth: Working with industry is a critical component to what CASL is doing -- indeed, it is the strong interactions and teaming amongst national laboratories, universities and industry that I believe is the hallmark of CASL and an appropriate funding model for multi-disciplinary projects moving forward. In this particular case, we are working closely with Westinghouse and the Electric Power Research Institute to ensure that we have sufficient understanding of the fuel failure mechanisms and the current state of the art used by industry to model fuel failure. This is complemented by access to industry data for model validation, and in developing the high-performance computing workflow.