Detailed neutronic modelling of the CROCUS research reactor using APOLLO3® transport code.

The deterministic transport code APOLLO3 R developed at CEA was used to setup the
2D and 3D neutronic models of the zero-power, water-moderated experimental reactor
CROCUS, operated by Swiss Federal Institute of Technology in Lausanne, in order to
verify the computational methodology and apply it to the interpretation of experiments
conducted under the CORTEX European project related to neutron noise measurements
in which CEA participates. The variants of the self-shielding calculation based on fine
structure method were analysed and a fully heterogeneous 2D description of the reactor
is tested with different discretisation options using the method of characteristics. The
homogeneous model intended for the discrete ordinates, short characteristic calculation
is also analysed with the emphasis on the production of equivalent cross sections. The
reaction rates preserving equivalent cross sections are set on the basis of the whole 2D
domain used as reference homogenisation problem.