The VENUS-F Reactor for Nuclear Data Validation

Integral experiments for nuclear data validation have been carried out at the fast zero-power reactor VENUS-F at the Belgian Nuclear Research Centre SCK " CEN since 2011. VENUS-F serves as a mock-up of MYRRHA, a fast, lead-bismuth cooled reactor/accelerator-driven system. First, solid lead was used as a coolant simulator and reflector at VENUS-F. In 2016, all lead in VENUS-F fuel assemblies was replaced by bismuth (in total, 625 kg), and a new experimental campaign was carried out with the aim of validating bismuth properties in integral experiments, mainly in the neutron energy region from 1 keV up to 10 MeV. Since 2017, lead and bismuth have been combined in fuel assemblies to simulate lead bismuth eutectic. An overview of the integral experiments is presented in this paper. Fission rate spatial distributions are compared with Monte Carlo calculations using various nuclear data libraries. The importance of accurate knowledge of material composition is discussed using high-purity bismuth samples (99.99 %) as examples. These were characterized by neutron activation analysis at SCK "CEN, mass spectrometry by the supplier (EVOCHEM), and neutron resonance capture analysis at the GELINA facility of the European Commission Joint Research Centre.