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May 3, 2017

UW-Madison analysis provides insight for ITER

Written By: Adam Malecek

While the ITER facility under construction in southern France is still years away from being completed, the ITER Organization already knows what radiation levels to expect within the building following fusion experiments—and as a result, how to keep people in the building safe—thanks to the work of University of Wisconsin-Madison engineers.

Once the massive construction and assembly efforts are completed, the ITER building will house the world’s largest tokamak, a magnetic fusion device that has been designed to prove the feasibility of fusion as a large-scale and carbon-free source of energy based on the same principle that powers the sun and stars.

Paul P.H. Wilson
Paul Wilson

For more than a decade, Grainger Professor of Nuclear Engineering Paul Wilson and his collaborators have been developing software tools to model complex nuclear energy systems. And since ITER will be the most complex nuclear fusion system ever created, it offered an excellent opportunity for Wilson and his students to apply their software tools to solve a difficult problem.

They used these tools to estimate the radiation levels within the entire ITER building after the reactor is shut down.

“It was a really big effort,” Wilson says. “However, UW-Madison is one of the leading places in the country to do an analysis of ITER.”

Wilson says calculating radiation levels is important for the safety of workers who will be maintaining the ITER equipment. “And since ITER is in the process of being built, our work is influencing the design and maintenance schedules of the equipment,” he says.

For example, since the ITER engineers know what the radiation level inside the building will be, they can determine how long technicians can safely work inside the building to maintain the equipment. As a result, if maintenance for a certain piece of equipment will require more than the allotted time, ITER might need to make changes to that component to, for instance, allow workers to easily disconnect it and remove it from the room so they can perform the maintenance in a safe place.

Wilson’s software tools are exceptional at analyzing objects with very complex geometries—and importantly, those geometries can originate from a CAD (computer-aided design) model developed using standard CAD software. Wilson’s tools can consume these CAD models and produce a computational model for a full, detailed analysis.

For the ITER project, Wilson and his team took the individual CAD models provided by the designers of the ITER tokamak building and assembled them all into a large model.

Fusion experiments in ITER will produce neutrons, and Wilson and his students used their tools along with software from Los Alamos National Laboratory to map how those neutrons spread inside the tokamak building.

“We’ve got this big, cathedral-sized building full of slightly radioactive material,” Wilson says. “We ran simulations with additional software on our model to figure out how much radiation there is everywhere in the building from that material.”

Wilson’s tools can dramatically speed up the process of producing a model that engineers can use for a comprehensive analysis.

“In the absence of our software, someone has to take this complex CAD geometry and figure out how to manually represent it, and it can take a person months to do that,” he says. “And so we’re providing a capability where, in the best case, it takes only days of time to make the models useable. In the most complex cases, it could take weeks or even months, but it’d still be many fewer months than with the manual process.”