FROM MACRO- TO MICROSCALE HYDRAULIC SIMULATIONS OF A REACTOR PRESSURE VESSEL IN THE FRAMEWORK OF THE SYSTEM CODE ATHLET

Nikonov S.P., NRC “Kurchatov Institute”, Moscow, Russia, I. Pasichnyk, K. Velkov, GRS mbH, Garching, Germany

22nd Symposium of AER on VVER Reactor Physics and Reactor Safety (2012, Průhonice, Czech Republic)
NEUTRON KINETICS AND REACTOR DYNAMICS METHODS

Abstract

In the present paper the possibility of performing a multiscale modeling of the hydraulics of a
reactor pressure vessel (RPV) using the system code ATHLET ¹ is considered. The main
focus of the work is the modeling of the active core. There are several length scales that can
be used in the modeling of RPV, namely 1) macroscale, or the set of fuel assemblies (sectors);
2) mesoscale or an individual fuel assembly; and 3) microscale or a pinwise modeling of one
or several fuel assemblies. In all above mentioned cases the modeling structures are
represented by the systems of parallel channels, hydraulically coupled with each other in the
transversal direction (in the absence of the walls). The modeling allows using both meso- and
microstructures and the object nodalization of the upper and lower part of the reactor uses
macro- and mesostructures. To improve the modeling of the flow in the transverse direction
the convection term in the ATHLET momentum equation is corrected to give the possibility
to simulate two- and three-dimensional flows.

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