I understand that that the energy released from splitting atoms is used to heat up water into steam and turn a turbine, but how are the atoms actually split?
In: Engineering
Think of a Uranium atom like it’s sitting in a ditch on top of a hill. If you give it a little push it’ll roll down the hill, putting out much more energy than you put in to get it rolling.
The little push they need is a Neutron. There are plenty of isotopes called “startup neutron sources” available that spontaneously emit fast neutrons, but once it’s running, the source is the splitting uranium atoms themselves. They don’t just split in two, they might split into a few things and some of those leftover parts are extra Neutrons to go split other atoms.
How often this happens is based on density and heat, so in most reactor designs there are “control rods” that can be inserted to absorb neutrons if it gets too hot.
When a fissile atom is hit with a neutron with the right amount of energy, the atom will go into an excited state where it oscillates and wobbles, eventually wobbling too much (kind of like resonating), and stretch into a dumbbell shape far enough apart that the “strong” nuclear force can no longer hold it together and it splits apart.
The first neutron can come from spontaneous fission (the atom randomly splits). However spontaneous fast fission doesn’t make enough neutrons for us to safely monitor and control the reactor during startup. For the first startup of a fresh core we insert a neutron source like californium -252 to help boost the neutron count high enough so that we can monitor the startup and control it.
After the first startup, the fuel is irradiated and the nuclear waste products produce enough neutrons as they break down. The nuclear waste byproducts in the irradiated fuel supply the neutrons. We can take the sources out and we only need to put them back in if the core is shut down for many years or if the core is replaced with entirely fresh fuel
The atoms are really unstable and looking for an excuse to break down to a more stable state. To do that, you knock ’em with neutrons. This causes a chain reaction – after you hit one with a neutron, it breaks apart releasing energy and more neutrons, which hits other atoms that break apart and release more energy and more neutrons.
Latest Answers