Uranium 233 Fission
Uranium 233 is a very good fissile isotope and its fission cross-section for thermal neutrons is about 531 barns (for 0.0253 eV neutron). For fast neutrons its fission cross-section is on the order of barns. Most of absorption reactions result in fission reaction, but a minority results in radiative capture forming 234U. The cross-section for radiative capture for thermal neutrons is about 45 barns (for 0.0253 eV neutron). Therefore about 6% of all absorption reactions result in radiative capture of neutron. About 94% of all absorption reactions result in fission. The capture-to-fission ratio is much smaller than the other two major fissile fuels 235U and 239U.
Typically, when uranium 233 nucleus undergoes fission, the nucleus splits into two smaller nuclei (triple fission can also rarely occur), along with a few neutrons (the average is 2.48 neutrons per fission for thermal fission) and release of energy in the form of heat and gamma rays. The average of the fragment atomic mass is about 112, but very few fragments near that average are found. It is much more probable to break up into unequal fragments, and the most probable fragment masses are around mass 93 (strontium) and 137 (xenon).Most of the fission fragments are highly unstable (radioactive) nuclei and undergo further radioactive decays to stabilize itself, therefore part of the released energy is radiated away from the reactor (See also: Reactor antineutrinos). On the other hand most of the energy released by one fission (~168MeV of total ~200MeV) appears as kinetic energy of these fission fragments. The fission fragments interact strongly with the surrounding atoms or molecules traveling at high speed, causing them to ionize. Creation of ion pairs requires energy, which is lost from the kinetic energy of the charged fission fragment causing it to decelerate. The positive ions and free electrons created by the passage of the charged fission fragment will then reunite, releasing energy in the form of heat (e.g. vibrational energy or rotational energy of atoms). This is the principle how fission fragments heat up fuel in the reactor core.