Question: Why is graphite so susceptible to damage from neutron irradiation?

James Boone answered on 19 Mar 2012:

That’s a really good question! Graphite isn’t particularly susceptible to damage from neutron radiation, it’s just that it’s quite a good material at withstanding the damage. Any material would be damaged by the bombardment of neutrons especially at the energy which they are produced in a nuclear reactor. Graphite was specially chosen by engineers and scientists as the material for the job because it’s very good at slowing down neutrons without the damage affecting the structural integrity too much, neither does it absorb the neutrons, so they can continue to maintain a chain reaction in the Uranium fuel. Even after being exposed to the neutrons for many years, the graphite is still mechanically strong, but it can crack and change dimensions! All these changes are carefully monitored and ultimately if the Graphite loses its strength, the whole power plant has to be shut down for good, as it can’t be replaced. There is simply too much graphite in the core to replace it all cost effectively and safely. I hope I’ve answered your question clearly enough 🙂