Development and comparison of Monte Carlo techniques implemented in the MORET 4 code for the calculation of loosely coupled systems.
J. Miss, O. Jacquet, A. Nouri, MC 2000, 23-26 october 2000, Lisbonne (Portugal).
The performances of the Monte Carlo method and the easiness of its use
enable to calculate more and more complex con ﬁgurations.In some cases,when there
is little coupling of neutrons be ween the different ﬁssile media of the system,a careful
check of neutron simulation is needed.Within the framework of nuclear criticality,
the use of the curren codes and the reliabilityof their results suffer restrictions.In
fact,as was stressed byWhitesides in a famous article [1 ],the calculated keff becomes
erroneous under certain circumstances (often under-estimating the reactivityof the
system).In this paper,one shows some aspects of the di ﬃculty encountered when
calculating weaklycoupled systems.New developments have been performed in the
MORET4 code [2 ]to improve the calculation of keff in geometries including such weakly
coupled ﬁssile units.