Calculation of Sodium Cooled Fast Reactor Concepts. Preliminary results of an OECD NEA benchmark calculation

In this paper we present the results of our calculations of the OECD NEA benchmark on generation-IV advanced sodium-cooled fast reactor (SFR) concepts. The aim of this benchmark is to study the core design features, moreover the feedback and transient behaviour of four SFR concepts. At the present state, static global neutronic parameters, e.g. k_eff, effective delayed neutron fraction, Doppler constant, sodium void worth, control rod worth, power distribution; and burnup were calculated for both the beginning and the end of cycle. In the benchmark definition, the following core descriptions were specified: two large cores (3600 MW thermal power) with carbide and oxide fuel, and two medium cores (1000 MW thermal power) with metal and oxide fuel. The calculations were performed by using the ECCO module of the ERANOS code system at the subassembly level, and with the KIKO3DMG code at the core level. The former code produced the assembly homogenized cross sections applying 1968 group collision probability calculations; the latter one determined the core multiplication factor, the radial power distribution using a 3D nodal diffusion method in 9 energy groups. We examined the effects of increasing the energy groups to 17 in the core calculation. The reflector and shield assembly homogenization methodology was also tested: a “homogeneous region model” was compared with a “concentric cylindrical core” calculation. The breeding ratio was also determined for the beginning of cycle. (author)