Static analysis of the PDS-XADS LBE and gas-cooled concepts

Within the European Fifth Framework Program, Preliminary Design Studies of an Experimantal Accelerator Driven System (PDS-XADS) being supported by the European Commission are focussed on options employing molten Lead-Bismuth Eutectic (LBE) and helium gas coolants. Two of the options employ 80 MWth subcritical cores which are driven by a 600 MeV proton beam with a maximum current of 6 mA, the proton beam impinging either on a window or a windowless LBE target near the core center. By assuming, for example, one-batch operation, the fuel discharge burnup being consistently computed with the deterministic code ERANOS (Version 2.0) is ∼20 MWd/kg for the gas-cooled XADS and ∼25 MWd/kg for the LBE XADS. The larger source importance of the gas-cooled XADS ensures that these two values are relatively close in spite of the more negative reactivity level of the gas-cooled XADS. The gas-cooled XADS exhibits a much larger transport effect reflecting the strong anisotropy of scattering in the low density regions. However, the sensitivity to the characteristics of the external neutron source being precalculated with MCNPX and then used in the burnup calculations is quite small in both cases.