Supercomputers study reactor core behaviour

27 January 2010

A new computer algorithm that enables scientists to view nuclear fission in much finer detail has been developed by researchers at the US Department of Energy's (DoE's) Argonne National Laboratory (ANL). The code could be used in the development of new reactor designs.


Nuclear reactor simulator (ANL)

An elevation plot of the
highest energy neutron
flux distributions from an
axial slice of a nuclear
reactor core is shown
superimposed over the
same slice of the
underlying geometry
(Image: ANL)

The neutron transport code UNIC is being developed by a team of nuclear engineers and computer scientists at ANL which they said enables researchers to obtain a highly detailed description of a nuclear reactor core for the first time.


The calculations required to model the complex geometry of a reactor core requires massive computer memory capacity, far higher than most computers can handle. Therefore reactor modelling codes typically rely on various approximations, which ANL says, "limit the predictive capability of computer simulations and leave considerable uncertainty in crucial reactor design and operational parameters."


ANL said that it has successfully run the UNIC code at DoE computing facilities, home to some of the world's fastest supercomputers. Although still under development, ANL said that the code has already produced new scientific results.


For example, the Argonne team has carried out highly detailed simulations of the Zero Power Reactor experiments on up to 163,840 processor cores of the Blue Gene/P supercomputer at ANL and 222,912 processor cores of the Cray XT5 supercomputer at Oak Ridge National Laboratory, as well as on 294,912 processors of a Blue Gene/P at the Jülich Supercomputing centre in Germany. The Zero Power Reactor is an experimental nuclear reactor operated at low neutron flux and at a power level so low that no forced cooling is required. With UNIC, the researchers have successfully represented the details of the full reactor geometry for the first time and have been able to compare the results directly with the experimental data.


Andrew Siegel, head of ANL's reactor simulation group, said: "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 geometrics."

It "provides a powerful new tool for designers of safe, environmentally friendly nuclear reactors - a component of our nation’s current and future energy needs," according to ANL, which added that, "By integrating innovative design features with state-of-the-art numerical solvers, UNIC allows researchers not only to better understand the behaviour of existing reactor systems but also to predict the behaviour of many of the newly proposed systems having untested design characteristics."


Development of the UNIC code is primarily funded by the DoE's Office of Nuclear Energy through the Nuclear Energy Advanced Modelling and Simulation (NEAMS) program.


Researched and written

by World Nuclear News