Radiative captures of slow neutrons
Radiative capture competes with fission. Neutrons captured by the nuclei present in the core of reactors are lost for the chain reaction. The figure shows that for the three main fissile nuclei (uranium-235 and 233, plutonium-239), radiative capture concerns only 10-28% of the captures, while for uranium-238 and all non-fissile nuclei radiative capture amounts to around 100%. Percentages are given for slow neutrons that favors fissions. Fast neutrons are able to fission nuclei known as non-fissile such as uranium-238 and actinides.