Critical albedo search applied to a UOX fuel assembly: evolution of the surface albedo β(g) as a function of the number of fission cycles g. Blue: beginning-of-life conditions (slightly super-critical); red: higher burn-up (slightly sub-critical): the critical parameter search would fail, unless the speed of convergence is adjusted (green), in which case the algorithm converges to the sought value. Figure taken from reference [31]. (This figure is subject to copyright protection and is not covered by Creatice Commons License. Elsevier, 2018).