Neutron spectrometry in large iron and sodium assemblies

For the validation of differential cross section data neutron spectrum measurements in deep penetration single material benchmarks are of great value. At the Euracos facility consisting of a highly enriched U235 disk of 80 cm diameter thermal neutrons from 250 Kw Triga reactor are converted into fission neutrons which are in turn used to irradiate large blocks of iron (145x145x130 cm/sup 3/) or sodium (145x145x400 cm/sup 3/). In these assemblies the neutron spectra were measured as a function of the penetration depth in the energy range 15 KeV to 10 MeV using a combination of proton recoil spectrometers (proportional gas counters of different pressures and a liquid scintillator)