Fission Radioactivity

The "daughter" nuclei, are also radioactive and they beta decay:
¹³¹Sn (half-life is 56 seconds) and ⁹⁵Sr (half-life is 23.9 seconds) beta decay to
¹³¹Sb (half-life is 23.0 minutes) and ⁹⁵Y (half-life is 10.3 minutes) which also beta decay to
¹³¹Te (half-life is 25.0 minutes) and ⁹⁵Zr (half-life is 64.0 days) which also beta decay to
¹³¹I (half-life is 8.0 day) and ⁹⁵Nb (half-life is 35 days) which also beta decay to
¹³¹Xe and ⁹⁵Mo which are stable.

Ground-state fission occurs in heavy nuclei (mass larger than 230). Fission also can occur in nuclear reactions

For more reading see Wikipedia's nuclear fission