Radial cut of the fundamental (top) and first excited eigenmode (bottom) of the fission source distribution of the EOLE critical facility, formerly operated by CEA. The eigenmodes have been computed using the fission matrix (K _i, j ) capability of TRIPOLI-4. Figure adapted from reference [30]. (This figure is subject to copyright protection and is not covered by Creatice Commons License. Elsevier, 2021).