FOIL ACTIVATION STUDIES OF SPECTRAL VARIATIONS IN THE MUSE4 CRITICAL CONFIGURATION

The MUSE4 phase of the MUSE (Multiplication with an external source) programme has been launched recently at the MASURCA facility at Cadarache (France). This series of integral experiments relevant to accelerator driven systems (ADSs) consists in studying a reference critical fast-spectrum configuration, followed by three different subcritical modifications of the same, each driven by an external neutron source produced via an accelerator. The presence of the accelerator tube in the core creates new types of heterogeneities, the effects of which need to be modelled and quantified by appropriate calculational tools. A part of the unique ADSrelevant validation base being provided by MUSE4 are results from a wide range of activation foil measurements covering various reaction rates, both with and without thresholds. Each experimental campaign consists in irradiating the foils in different representative locations to characterise the new types of spectral variations. This paper presents experimental results obtained in the reference critical MUSE4 configuration. Comparisons are made with calculations using both deterministic (ERANOS-1.2) and stochastic (MCNP-4C) codes in conjunction with different data libraries (JEF-2.2, ERALIB1, ENDF/B6). Good agreement has been obtained between calculation and experiment in most cases. However, significant discrepancies have been found for the high-threshold reaction rates inside and around the central diffusing lead region, indicating the need for more detailed investigations in this context.