{"id":25149,"date":"2019-09-19T07:44:26","date_gmt":"2019-09-19T07:44:26","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=25149"},"modified":"2023-06-13T07:46:01","modified_gmt":"2023-06-13T07:46:01","slug":"spontaneous-fission","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radioactive-decay\/spontaneous-fission\/","title":{"rendered":"Spontaneous Fission"},"content":{"rendered":"
Spontaneous fission<\/strong> is a decay process in which an unstable nucleus spontaneously splits into smaller parts (lighter nuclei). Spontaneous fissions release neutrons as all fissions do, contributing to neutron flux in a subcritical reactor<\/a>. Spontaneous fission<\/strong> is feasible over practical observation times only for mass numbers greater than 232.<\/div><\/div>\n

In general, nuclear fission<\/strong> is a nuclear reaction<\/a> in which the nucleus of an atom splits<\/strong> into smaller parts (lighter nuclei). The fission process often produces free neutrons<\/a> and photons<\/a> (in the form of gamma rays<\/a>) and releases a large amount of energy<\/strong>. Nuclear fission is either a nuclear reaction<\/strong> or a radioactive decay process<\/strong> in nuclear physics. The case decay process is called spontaneous fission,<\/strong> a very rare process.<\/p>\n

\"\"<\/a><\/strong>Spontaneous fission<\/span><\/strong>\u00a0is also possible if we study the\u00a0<\/span>nuclear binding curve<\/span><\/a>, and this decay is energetically possible for a nucleus having A > 100. Although spontaneous fission is expected to become more probable as the mass number increases, it is still a rare process, even in uranium.<\/span><\/p>\n

Spontaneous fission<\/strong> is feasible over practical observation times only for mass numbers greater than 232. For example, 232<\/sup>Th, 235<\/sup>U, and 238<\/sup>U are primordial nuclides<\/a> and have left evidence of undergoing spontaneous fission in their minerals.<\/p>\n

For heavy transuranic elements, the spontaneous fission transition rate increases with the mass number, and it may become the dominant decay mode at mass numbers greater than 260.<\/p>\n

Similarly, as for alpha decay<\/a>, spontaneous fission occurs due to quantum tunneling<\/a>. Spontaneous fissions release neutrons as all fissions do, contributing to neutron flux in a subcritical reactor<\/a>. Radioisotopes for which spontaneous fission is not negligible can be used as neutron sources. For example, californium-252 (half-life 2.645 years, SF branch ratio about 3.1 percent) can be used for this purpose.<\/p>\n

The spontaneous fission<\/strong> of naturally occurring isotopes of uranium (uranium-238 and uranium-235) does leave trails of damage in the crystal structure of uranium-containing minerals when the fission fragments recoil through them. A radiometric dating technique based on analyses of these damage trails, or tracks, left by fission fragments in certain uranium-bearing minerals and glasses is known as fission track dating<\/strong>.<\/p>\n

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Spontaneous Fission of Certain Nuclei<\/h2>\n

The main isotopes, which have to be considered in the fuel cycle of all commercial light water reactors, are:<\/p>\n

Isotopes of uranium<\/strong><\/p>\n