What Does Neutron Embrittlement Mean?
Embrittlement on its own is the loss of ductility in a material, thus making it brittle. This can have different mechanisms depending on the metal involved. Neutron embrittlement is caused by neutron radiation. It also causes the buildup of Wigner energy as well as neutron-induced swelling.
Neutron radiation does not ionize atoms like charged particles, because they do not have a charge. Neutron interactions have great ionizing power, and since they lack charge, their penetration is felt more than that of alpha or beta radiation. Gamma radiation is powerful, but neutron radiation can sometimes be more powerful than it.
Corrosionpedia Explains Neutron Embrittlement
Neutron radiation reduces the toughness of materials. This is the case in steel used for nuclear vessels. The pressure vessel constitutes the most important part of the nuclear reactor, with the nuclear fuel accommodated in the vessel. The fissile nuclide undergoes exothermic nuclear reaction chains, thus generating useful energy. The only isotope fissile with thermal neutrons is uranium 235 (U-235). The fission reactions of U-235 emit high-energy electrons that impact the inner side of the vessel. The collisions modify the mechanical properties of the steel, leading to embrittlement through a complex series of events on a microstructural and nano scale—this causes the decrease in toughness.