''TIBERE'' a calculational method of the effect of lattice heterogeneity on the neutron leakage

Abstract

The flux calculation in a heterogeneous assembly in APOLLO and APOLLO-2 codes is based on the collision probability method On the contrary, the neutron leakage calculation is accomplished for a flux-weighted homogenized assembly, which is a good approximation in the case of a non-voided assembly (PWR in normal conditions) If an assembly contains voided zones (for example as the consequence of LOCA) or if the reactor, in normal operation, contains void or transparent media (Na), the approximation may become much more debatable The formalism proposed here treats the leakage taking into account the heterogeneity of the medium, the leakage being treated as a type of reaction analogous to others This formalism is introduced in APOLLO-2 code as a module and uses only tools similar to those used for the calculation of the flux (author)