The trap of resonant captures
The curve of the percentages of neutrons capture in collisions with uranium-238 nuclei shows the presence of a "forest" of resonances below an energy of 10 keV. At a resonant energy, not only the nucleus seems to grow, but also the capture probability becomes large. These resonances are many, sometimes very close from each other. Between the resonances, the uranium nucleus becomes almost invisible to neutrons and the capture probability drops almost to 0.