CHARACTERIZATION OF A REPRESENTATIVE VVER-440 FUEL ROD WITH THE STATISTICAL ENIGMA
22nd Symposium of AER on VVER Reactor Physics and Reactor Safety (2012, Průhonice, Czech Republic)
NEUTRON KINETICS AND REACTOR DYNAMICS METHODS
Abstract
Heat transfer in the gas gap of a fuel rod affects the behaviour of the reactor core also in the scale
of the whole reactor. In the VTT?s reactor dynamic codes, heat transfer in a gas gap is usually
characterized by some temperature dependent curve that is given as input data. Typically burnup
is taken into account in a rather simple way, e.g. by using different curves for fresh assemblies
and one, two and three year old fuel assemblies. Implementation of a detailed fuel model in the
reactor dynamics codes would not be a suf?cient way to model the gas gap. As the properties
of a fuel rod change remarkably during its normal reactor life, the initial state of the transient
must be somehow determined.
In this paper, the statistical version of the fuel performance code ENIGMA has been used to
determine the properties of a representative VVER-440 fuel rod at various points of its reactor
life. The aim was to ?nd such a way to model the gas gap properties, that could be utilized in
VTT?s reactor dynamic codes TRAB-3D and HEXTRAN.