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Going Nuclear: Notes from the officially unofficial book tour
I work in the analytical labs at one of Europe’s oldest and largest nuclear sites: Sellafield, in northwestern England. I spend my days at the fume hood front, pipette in one hand and radiation probe in the other (and dosimeter pinned to my chest, of course). Outside the lab, I have a second job: I moonlight as a writer and public speaker. My new popular science book—Going Nuclear: How the Atom Will Save the World—came out last summer, and it feels like my life has been running at full power ever since.
Michel Saliba, Vincent Lamirand, Wilfried Monange, Fanny Vitullo, Mathieu Hursin, Andreas Pautz, Oskari Pakari
Nuclear Science and Engineering | Volume 200 | Number 1 | March 2026 | Pages S406-S414
Research Article | doi.org/10.1080/00295639.2025.2456411
Articles are hosted by Taylor and Francis Online.
Analyzing neutron noise in zero-power reactors provides information about integral parameters, such as the prompt decay constant . This information can be used to validate codes that predict said parameters, or time-dependent behavior, particularly reactor transients. The CROCUS zero-power research reactor has been widely used for conducting noise experiments and has recently been enhanced with a new neutron detection system SAFFRON. This system includes an array of about 150 miniature neutron detectors evenly dispersed throughout the core, allowing for three-dimensional (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 . Our results, derived from the Rossi- method, aligned with the predictions from the Serpent 2 Monte Carlo code, which utilized the Lawrence Livermore National Laboratory FREYA library for fission. The agreement was within 1 of the estimated uncertainties. We notably observed that based on previous experiments, using all 150 detectors does not achieve the levels of detection efficiency (in counts per fission) expected to be 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 the success of the neutron noise technique. We also explored the cross-spectral density method for different combinations of SAFFRON detectors, which gave consistent results with the Rossi- method. In addition, uncertainty estimation methods, including the bootstrap method, were applied to SAFFRON, addressing both temporal and spatial aspects. We discuss the benefits of using bootstrap methods for estimating the uncertainty of the prompt decay constant, which we found often underestimated when using the covariance matrix from a standard nonlinear fit. 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-resolution reactor physics experiments.