Abstract
Accurate prediction of the neutron and temperature distributions within an operating nuclear reactor
requires the solution of multiple coupled physics equations. In a light water reactor (LWR), there is a
very strong coupling between the power distribution (governed by the radiation transport equation) and
the temperature and density distributions (governed by a thermal di usion equation in combination with
a fluid flow model). This study aims to begin to quantify the impact of such feedback mechanisms as
well as identify numerical diculties associated with such multiphysics problems. A description of the
multiphysics model and current solution strategy within the Exnihilo code package will be presented,
along with numerical results for a representative 3 3 PWR ‘mini-assembly.’
