A new computer algorithm developed by researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory allows scientists to view nuclear fission in much finer detail than ever before.

A team of nuclear engineers and computer scientists at Argonne National Laboratory are developing the neutron transport code UNIC, which enables researchers for the first time to obtain a highly detailed description of a nuclear reactor core.

Such calculations exhaust computer memory of the largest machines, and therefore reactor modeling codes typically rely on various approximations. But approximations limit the predictive capability of computer simulations and leave considerable uncertainty in crucial reactor design and operational parameters.

"The UNIC code is intended to reduce the uncertainties and biases in reactor design calculations by progressively replacing existing multilevel averaging techniques with more direct solution methods based on explicit reactor geometries," said Andrew Siegel, a computational scientist at Argonne and leader of Argonne's reactor simulation group.

UNIC has run successfully at DOE leadership computing facilities, home to some of the world's fastest supercomputers, including the energy-efficient IBM Blue Gene/P at Argonne and the Cray XT5 at Oak Ridge National Laboratory. Although still under development, the code has already produced new scientific results.

"An elevation plot of the highest energy neutron flux distributions from an axial slice of the reactor is shown superimposed over the same slice of the underlying geometry. This figure shows the rapid spatial variation in the high energy neutron distribution between within each plate along with the more slowly varying, global distribution. The figure is significant since UNIC allows researchers to capture both of these effects simultaneously. (Credit: Image courtesy of Argonne National Laboratory)"

Source: Argonne National Laboratory