CASL completes 10-year mission

August 17, 2020, 9:30AMNuclear News

The Department of Energy established the Consortium for Advanced Simulation of Light Water Reactors (CASL) at Oak Ridge National Laboratory in 2010 as a national collaboration of government, academia, and industry to help the nuclear industry extend the life of the current reactor fleet and develop more efficient next-generation reactors. On August 13, ORNL issued a news release and video to celebrate the achievements of CASL, which concluded its mission in June.

Program goals: About 250 people were involved in CASL in any given year, and about 750 participated over the span of the project. Together, they worked to do the following:

Accurately predict and reduce instances of undesirable boiling conditions to increase fuel performance and core power.

Predict and manage “crud,” the deposits that can form on fuel rods and reduce their efficiency and lifespan.

Predict fuel pellet and cladding integrity during normal operation and postulated accident scenarios to give power plant operators greater flexibility.

Predict how neutrons interact with large reactor components to provide a guide for which materials are likely to degrade when, and to help reactor owners decide when to replace parts for improved performance.

VERA’s tools allow a virtual window inside the reactor core, down to a molecular level. Image: ORNL/DOE

Insights from VERA: To make those predictions, CASL developed the Virtual Environment for Reactor Applications (VERA), a software suite based on reactor physics, thermal hydraulics, chemistry, and fuel performance that allows insight into every part of a reactor. A milestone was reached about five years into the CASL program, when VERA accurately simulated the 2016 startup of the Tennessee Valley Authority’s Watts Bar-2 pressurized water reactor.

“Until the virtual reactor showed that it could match reactor data, everybody bought into the potential, but the industry had difficulty envisioning how it could be applied to solve real-life problems,” said former CASL director Doug Kothe. To date, VERA has been used to accurately simulate more than 200 fuel cycles, representing two-thirds of the U.S. operating reactor fleet, and has also modeled as-yet-unbuilt reactor types.

“We showed that high-performance computing, putting the best models and algorithms into the computer to emulate the reactor, really does give you very high-confidence results as to what’s going on,” Kothe said. “Because of CASL, you can design reactors in the computer with high enough confidence that when you go to build the reactor, you’re really confirming the design.”

Path to commercial licensing: Last year, CASL worked to ensure that VERA was in compliance with ASME’s Nuclear Quality Assurance-1, which involved adapting procedures, increasing documentation, writing detailed manuals, and training. VERA is now available for commercial licensing, and the first license was granted to the Electric Power Research Institute, which was involved in CASL from the beginning, in March 2020.

Users can access the software suite through the DOE Office of Nuclear Energy’s new high-performance computer at Idaho National Laboratory, called Sawtooth, which provides cloud supercomputing focused on nuclear energy simulations.

“This is not a code you can run on your laptop,” said Dave Kropaczek, a chief scientist with CASL who became its director in 2018.

Read ORNL’s news release for more insights from those involved in CASL over the past 10 years.

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