In the case of Cs the precursor to this isotope is stable Cs which is formed by the decay of much longer lived xenon and iodine isotopes. No Cs is formed without neutron activation as Xe is a stable isotope. As a result of this different mode of formation the physical location of Cs can differ from that of Cs.
These fission yields were calculated for U assuming thermal neutrons (0.0253 eV) using data from the chart of the nuclides.