Publication
Analyzing neutron noise in zero power reactors is a valuable tool for gaining insights into integral parameters, such as the prompt decay constant α. This information can be used to validate codes that predict said parameters, or time-dependent behavior, particularly reactor transients. The zero-power research reactor CROCUS has been widely used for conducting noise experiments and has recently been enhanced with a new detection system, SAFFRON. This system includes an array of 150 miniature neutron detectors evenly dispersed throughout the core, allowing for 3D spatial detection capabilities. We conducted a neutron noise experiment using the 3D array to test this new system to determine the prompt decay constant α. Our results, obtained using the Rossi-α method, showed agreement with Serpent 2 Monte Carlo code (using the LLNL FREYA library for fission) predictions within 1σ of the estimated uncertainties. We notably observed that, based on previous experiments, using all 150 detectors did not achieve the levels of detection efficiency (i n co unts pe r fission) necessary to observe the fission chain decay - yet we still observe the decay with comparatively high statistical significance. We therefore show experimentally, that the spatial extent of the detection system is an important parameter in the prediction of neutron noise technique success. The results also indicate that SAFFRON is a powerful measurement tool that can be expanded for use in active perturbation experiments, 3D flux maps, and other high-fidelity reactor physics experiments.