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Three californium isotopes with significant half-lives are produced, requiring a total of 15 neutron captures by uranium-238 without nuclear fission or alpha decay occurring during the process. [ 57 ] 253 Cf is at the end of a production chain that starts with uranium-238, and includes several isotopes of plutonium , americium , curium , and ...
Californium (98 Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 245 Cf in 1950. There are 20 known radioisotopes ranging from 237 Cf to 256 Cf and one nuclear isomer, 249m Cf.
For example, the third atom of nihonium-278 synthesised underwent six alpha decays down to mendelevium-254, [2] followed by an electron capture (a form of beta decay) to fermium-254, [2] and then a seventh alpha to californium-250, [2] upon which it would have followed the 4n + 2 chain (radium series) as given in this article.
Known as "chain yield" because it represents a decay chain of beta decay. Isotope and element yields will change as the fission products undergo beta decay, while chain yields do not change after completion of neutron emission by a few neutron-rich initial fission products (delayed neutrons), with half-life measured in seconds.
Berkelium-247 can maintain a chain reaction both in a thermal-neutron and in a fast-neutron reactor, however, its production is rather complex and thus the availability is much lower than its critical mass, which is about 75.7 kg for a bare sphere, 41.2 kg with a water reflector and 35.2 kg with a steel reflector (30 cm thickness).
Californium is a strong neutron emitter, and would pollute the back end of the fuel cycle and increase the dose to reactor personnel. Hence, if minor actinides are to be used as fuel in a thermal neutron reactor, the curium should be excluded from the fuel or placed in special fuel rods where it is the only actinide present.
A subcritical mass is a mass that does not have the ability to sustain a fission chain reaction. A population of neutrons introduced to a subcritical assembly will exponentially decrease. In this case, known as subcriticality, k < 1. A critical mass is a mass of fissile
In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic process. Spontaneous fission is a dominant decay mode for superheavy elements, with nuclear stability generally falling as nuclear mass increases. It thus forms a practical limit to heavy element nucleon number.