IRPhEP Evaluation of VENUS 9 and VENUS 7 Experiments

The zero-power reactor VENUS (Vulcain Experimental Nuclear Study) was built in 1963–1964 at CEN-SCK, Mol, Belgium, as a nuclear mock-up of a projected spectral shift marine reactor called VULCAIN. The facility was modified in 1966 and 1967 in preparation for carrying out a series of critical experiments for the Belgian Plutonium Recycle Programme (PRP), which was partially supported by EURATOM. This was the VENUS-PRP program that took place between 1967 and 1975. VENUS-PRP-9 and VENUS-PRP-9/1, and VENUS-PRP-7 were two series of these PRP configurations that were carried out in 1967–1968 and that have recently been subject to evaluations as part of the Organisation for Economic Co-operation and Development, Nuclear Energy Agency International Reactor Physics Experiment Evaluation Project (IRPhEP). The VENUS-PRP-9 and VENUS-PRP-9/1 configurations focused on the study of the power distribution across the boundary between a standard UO₂ fuel region, enriched to 4 wt% ²³⁵U, and a mixed oxide fuel region made of UO₂, enriched to 3 wt% ²³⁵U with ∼1 wt% PuO₂, simulating a one-cycle burnt fuel. The IRPhEP evaluation focused on evaluating reaction rates and powers measured along a line that crossed the boundary between the two regions. In the VENUS-PRP-7, VENUS-PRP-7/1, and VENUS-PRP-7/3 series—which used essentially the same fuel pins—reactivities, reactivity worths of substituted and removed fuel pins, and radial fission rate distributions were measured; these quantities were evaluated in the framework of the IRPhEP project.