MOX assembly design at the VENUS-F Reactor for the representativity study of MYRRHA

The design of new-concept nuclear reactors often requires the operation of dedicated ex-perimental facilities. To support the design of MYRRHA ADS, the VENUS zero power reactor was renewed to its current fast spectrum version, VENUS-F. To investigate the fast neutron data on lead, bismuth and 238U, the VENUS-F core was loaded with lead and bismuth as coolant simulator and with 30% w.t.-enriched metallic uranium fuel. Since MYRRHA will be loaded with 30% w.t.-enriched MOX fuel, tailored MOX-core experiments are planned at VENUS-F. In the following, a number of possible VENUS-F MOX assembly designs are simulated with a focus on k∞ and βeff. Sensitivity profiles of k∞ and βeff to nuclear data are computed and the nuclear data uncertainty is propagated to them from the JENDL-4.0u evaluation. To assess the design performance, a representativity study is performed on k∞ and βeff. At the level of the fuel assembly active part representativity, which is the scope of this work, all the proposed designs proved to give very promising representativity results, often above 0.9.