Design of an Open-Loop Pile-Oscillation Program in the CROCUS Reactor

As a follow-up to the CEA-EPFL PETALE experimental program on stainless steel nuclear data, the EPFL initiated an open-loop pile-oscillation experimental program in the CROCUS reactor: BLOOM. A reproduction of the critical experiments of PETALE, the program intends to provide high-precision experimental data that will allow to complement them, but also directly tackle potential biases in their interpretation. In preparation, simulations and analysis scripts were developed based on prior know-how on modulation experiments modeling, and the analysis methods developed and validated by the CEA for their open-loop pile-oscillation program MAESTRO-SL. A quarter of the core is scouted to decide on the location of the experimental channel by performing Monte Carlo simulations with Serpent2. Simulations are also used to estimate the reactivity worth, and the impact on reaction rates in detectors of foreseen samples. Moreover, to maximize the program output, the design study includes the propagation of the iron nuclear data uncertainties on these two quantities and compares them to expected measurement uncertainties. The study’s results predict that a factor of ten or more is expected between the nuclear data uncertainties and statistical uncertainties for the different quantities of interest, with a duration of the experiments of 1 h. Future developments include the addition of new detectors for core and sample monitoring, which will allow a reduction of the duration of the experiments to 20 min.