When designing advanced reactors, researchers decided that in order to think big, they would first have to think small.

That work is under way at the Idaho National Laboratory (INL) where scientists are solving complex physics problems in manageable chunks and knitting them together in a cohesive “mesh.”

The results will help the U.S. Department of Energy lab design the next generation of reactors—candidates for the Global Nuclear Energy Partnership and the Next Generation Nuclear Plant, two federal government programs that center around state-of-the-art reactors.

These plants would differ fundamentally from present-day reactors, thus requiring a paradigm shift for computational physics.  To develop next-generation reactors, computer scientists need innovative models that work in three dimensions, are more flexible and reduce the reliance on experiments.

“These reactors are really going to be very efficient and reliable,” said Ronaldo Szilard, head of the lab’s nuclear science and engineering division.  “In order to have effective designs, we’re going to need new models with much better fidelity.”

Traditional computer models can approximate the behavior of present-day reactors.  However, those models were designed by analyzing repetitive test-reactor experiments, the results of which can only be applied in a single dimension and under very specific conditions.  If the new reactor’s design indeed differs from its predecessors in significant ways—whether because of the use of higher temperatures, new materials or safety features—those conditions could be unmet with older models.

Enter the new approach of solving small issues and creating meshes to pull the solutions together for a comprehensive approach to design.  As an added bonus, this approach allows collaboration among scientists at the Idaho facility, Los Alamos National Laboratory and Sandia National Laboratories.

“A high-quality mesh, in conjunction with advanced multiphysics methods, gives you the mathematics needed to couple physics problems together and lets you solve them without losing accuracy,” said Glen Hansen, a mathematician at the Idaho lab.

Multiphysics computer modeling will offer more accurate predictive capabilities, thus allowing designers to simulate nuclear reactors down to the atomic scale.  To accomplish this, the multiphysics team at INL is collaborating with its materials properties and performance department to study the effects of radiation on nuclear fuel. 

“The insights we gain from this work will help us create more accurate models of material properties, a critical component in developing and licensing the next generation of nuclear reactors,” physicist Tapan Desai said.

Although a truly predictive nuclear reactor simulation remains many years away, researchers say that the results of their work will be well worth the wait.