1. Challenges and strategies

As it produces more and more energy, nuclear fuel undergoes more and more modifications until it is deemed necessary to replace it for the reactor to function properly, which happens well before the fissile material is completely depleted. Fuel reactivity decreases as a result of the combined action of its depletion in fissile nuclei, insufficiently compensated by the formation of new fissile nuclei (plutonium 239, 241) through neutron capture of fertile (uranium 238) or fissile nuclei, and its enrichment in neutron collector nuclei (fission products, certain actinides). In addition, structural materials are subjected to severe stress, not only from the neutron bombardment to which they are subjected, but also, in the case of cladding, from thermal, mechanical and chemical interactions (corrosion) with the fuel, for which they form the first barrier, and with the heat transfer fluid. The...