One of the key issues concerning the design of new generation nuclear power plants and related fuel cycles is the development of flexible computational methods for determining the critical parameters of the core, the distribution of neutron fluxes, the time evolution of nuclear fuel composition (i.e. kinetics of poisons, burn-up, production and transmutation of actinides and fission fragments, isotopes decay).
This flexibility is necessary because the geometry and the structure of new reactor cores under study (GEN IV NPP), the energy spectrum of neutrons and nuclear fuel composition are extremely different. For GEN II NPP fuel analysis, several computational codes, such as ORIGEN, have been widely tested showing a fair consistency between the previsions and the measurements. When the analysis of fuel composition is focused of Research Reactor fuels or new generation NPP fuels though, more flexible computational methods are necessary in order to take into account the wide variety of core configurations, neutron energy spectra, fresh-fuel compositions and fuel high burn-up that characterize these plants. In this context, the integrated use of Monte Carlo computer codes and numerical multi-physics codes, appears to be extremely useful in terms of flexible management of input data and in terms of computing time. Aim of ARCO project is a sound validation of specific computational codes by comparison with direct measurements performed at known nuclear facilities (such as TRIGA reactor and sub-critical multiplicative complex SM1 of the University of Pavia).