The NEA has studied multiple recycling issues associated with various reactor systems fuelled with mixed-oxide (MOX) and published a series of computational physics benchmarks. This has led to improvements in the nuclear data libraries and calculation methods. Several benchmarks were completed comparing those findings with data from experiments. Previous benchmarks have concentrated mainly on PWRs, BWRs, VVER-1000s and FRs.
The present report provides an evaluation and analysis of the reactor period measurements carried out in the CROCUS reactor of the École polytechnique fédérale de Lausanne (EPFL) for several different delayed super-critical conditions. Two types of reactivity changes were measured employing an appropriate stable period technique in each case. The first series of experiments involved increasing the water level above the critical level. The second series was carried out by inserting/removing one of the absorber rods into/out of the core. The report also provides a benchmark model and the results obtained with different computer codes. The report will be of interest to reactor physicists and designers.