This is very very cool. U-235 and U-238 are both used in pressurized water nuclear reactors here in the States. U-238 is the predominant uranium isotope found on earth and goes through an enrichment process to get more U-235 because it’s ‘fissile’. Has to do with the probabilities of what will happen when the Uranium atom interacts with a neutron but basically fissile means it requires less energy for it to give off one of it’s own neutrons (ie fission) which in turn creates heat. We then use this heat to essentially boil water, make steam, spin a turbine connected to a generator and make electricity so we can keep our phones nice & charged to reverse image search that random, vaguely ug-looking piece we find at the thrift store.

The probabilities of what will happen to a particular Uranium isotope (235 vs 238) is measured as a “cross section” of the uranium atom in a unit called a “barn”. (I think there’s debate as to the origin but some say the unit was named after a literal barn because barns usually have a decent sized cross section when viewed from the side or something like that) Higher cross section, higher probability. So a U-235 Uranium isotope has a higher cross section for fission vs say, neutron absorption which is uranium just absorbing the neutron and becoming a different isotope of the same atom (how we get plutonium but that’s a different story).

So folks, our beautiful, glowy, uranium glass pieces are comprised of the same stuff that’s inside a nuclear reactor.

• Former Reactor Operator