21. These isotopes emit almost no ?-radiation, but undergo spontaneous fission with the associated emission of neutrons. 22. Most designs need enriched fuel so that there are more spontaneous fissions to act a seeds. 23. Spontaneous fission is feasible over practical observation times only for atomic masses of 232 amu or more.24. Plutonium-240 exhibits a high rate of spontaneous fission , raising the neutron flux of any sample containing it. 25. Thorium-232 is the lightest primordial nuclide that has left evidence of undergoing spontaneous fission in its minerals. 26. Element 41 ( niobium ) is theoretically unstable via spontaneous fission , but this has never been detected. 27. It was also found that some heavy elements may undergo spontaneous fission into products that vary in composition. 28. :Spontaneous fission is far too unreliable. 29. Spontaneous fission ends up with a probabilistic distribution of daughter products, which sets it apart from cluster decay.30. Mercury-180, producible from thallium-180, was found in 2010 to be capable of an unusual form of spontaneous fission .
