135Xe that does not capture a neutron decays to Cs-135, one of the 7 long-lived fission products, while 135Xe that does capture a neutron becomes stable 136Xe. Estimates of the proportion of 135Xe during steady-state reactor operation that captures a neutron include 90%, 39%â€“91% and "essentially all".
136Xe from neutron capture ends up as part of the eventual stable fission xenon which also includes 136Xe, 134Xe, 132Xe, and 131Xe produced by fission and beta decay rather than neutron capture.
133Xe, 137Xe, and 135Xe that has not captured a neutron all beta decay to isotopes of caesium. Fission produces 133Xe, 137Xe, and 135Xe in roughly equal amounts, but after neutron capture, fission caesium will contain more stable 133Cs (which however can become 134Cs on further neutron activation) and highly radioactive 137Cs than 135Cs.