- 2018 Prototypic neutronic parameters of thermal reactors were emulated in materials testing assemblies located in a 600 MWth metallic-fueled sodium fast reactor. Part of the outer reflector is composed of a moderating material such as graphite; all of the test assemblies were located in this designated thermalized region. Possible options for flux shaping assemblies and materials irradiation test assemblies are described. Both active and passive test assemblies are described. This paper focuses on PWR and VHTR in-core conditions. It is possible to modify the fast spectrum streaming from the driver to softer spectrum regions. In all configurations considered, the suggested options lead to significant neutron fluxes supporting accelerated neutron-induced damage studies.