Cold fission
Encyclopedia
Cold fission or cold nuclear fission
is defined as involving fission events for which fission fragments have such low excitation energy that no neutron
s or gamma
s are emitted.
Cold fission events have so low a probability of occurrence that it is necessary to use a high flux nuclear reactor to study them.
The first observation of cold fission events was in experiments on fission induced by thermal neutrons of uranium 233, uranium 235 and plutonium 239 using the High Flux Reactor at the Institut Laue-Langevin
in Grenoble, France. Other experiments on cold fission were also done involving 248Cm and 252Cf . A phenomenological interpretation was proposed by Gönnenwein and Duarte et al..
The importance of cold fission phenomena lies in the fact that fragments reaching detectors have the same mass that they obtained at the "scission" configuration, just before the attractive but short-range nuclear force becomes null, and only Coulomb interaction acts between fragments. After this Coulomb potential energy is converted in fragments kinetic energies, which-–added to pre-scission kinetic energies—is measured by detectors.
The fact that cold fission preserves nuclear mass until the fission fragments reach the detectors permits the experimenter to better determine the fission dynamics, especially the aspects related to Coulomb and shell effects in low energy fission. and nucleon pair breaking. Adopting several theoretical assumptions about scission configuration one can calculate the maximal value of kinetic energy as a function of charge and mass of fragments and compare them to experimental results.
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
is defined as involving fission events for which fission fragments have such low excitation energy that no neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s or gamma
Gamma
Gamma is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. It was derived from the Phoenician letter Gimel . Letters that arose from Gamma include the Roman C and G and the Cyrillic letters Ge Г and Ghe Ґ.-Greek:In Ancient Greek, gamma represented a...
s are emitted.
Cold fission events have so low a probability of occurrence that it is necessary to use a high flux nuclear reactor to study them.
The first observation of cold fission events was in experiments on fission induced by thermal neutrons of uranium 233, uranium 235 and plutonium 239 using the High Flux Reactor at the Institut Laue-Langevin
Institut Laue-Langevin
The Institut Laue–Langevin, or ILL, is an internationally-financed scientific facility, situated in Grenoble, France. It is one of the world centres for research using neutrons...
in Grenoble, France. Other experiments on cold fission were also done involving 248Cm and 252Cf . A phenomenological interpretation was proposed by Gönnenwein and Duarte et al..
The importance of cold fission phenomena lies in the fact that fragments reaching detectors have the same mass that they obtained at the "scission" configuration, just before the attractive but short-range nuclear force becomes null, and only Coulomb interaction acts between fragments. After this Coulomb potential energy is converted in fragments kinetic energies, which-–added to pre-scission kinetic energies—is measured by detectors.
The fact that cold fission preserves nuclear mass until the fission fragments reach the detectors permits the experimenter to better determine the fission dynamics, especially the aspects related to Coulomb and shell effects in low energy fission. and nucleon pair breaking. Adopting several theoretical assumptions about scission configuration one can calculate the maximal value of kinetic energy as a function of charge and mass of fragments and compare them to experimental results.