Investigation of ADS-Type heterogeneities in the MUSE4 critical configuration

The MUSE4 programme of ADS-related integral experiments has recently been completed at the MASURCA facility at Cadarache (France). Investigations have been carried out in a reference critical fast-spectrum configuration and related sub-critical core configurations driven by an accelerator. Among the various characteristics which need to be investigated are the peak power and the peak fast-neutron flux (damage in structural materials), the presence of the accelerator tube in the core creating new types of heterogeneities, the effects of which need to be modelled and quantified by appropriate calculational tools. In this context, different fission chamber traverses and various activation foil measurements in the MUSE4 programme have covered a wide range of threshold and non-threshold reaction rates. This paper presents the analyses of the corresponding experimental results from the reference critical MUSE4 configuration. Comparisons are made with calculations using both deterministic (ERANOS-2.0) and stochastic (MCNP-4C) codes in conjunction with different data libraries (JEF-2.2, ERALIB1, ENDF/B6). Significant discrepancies are observed, particularly for high-threshold reactions in the central lead diffusing region. Of the alternative calculational routes applied, the most appropriate ones for treatment of the ADS-type heterogeneities are found to be ERANOS-2.0 (with either JEF-2.2 or ERALIB1 data) and MCNP-4C in conjunction with its ENDF/B6 library.