JeffKoch said:A particular fission reaction has a neutron energy-dependent cross section, regardless of whether or not the neutron is "thermal". Are you asking for links to these energy-dependent cross sections?
dtsormpa said:Actually, what I meant by the question, was if the nucleus has a low activation energy, be heavy (A > 210) and has a specific ratio N/Z. It seems that only even N nuclei can fission by thermal neutron. Is that correct?
Well, the fissile nuclei have an odd mass number intially, but they form an even numbered nucleus up absorption of a neutron, e.g. U-233 + n -> U-234*, U-235 + n -> U-236*, Pu-239 + n -> Pu-240*, where the * indicates an excited state of the nucleus. The excited nucleus can fission or it can release a gamma-ray, in which case it forms a more stable nucleus. The point is that fissile nuclei are more likely to form an excited nucleus which does fission, as opposed to simply releasing a gamma ray (gamma decay).dtsormpa said:Actually, what I meant by the question, was if the nucleus has a low activation energy, be heavy (A > 210) and has a specific ratio N/Z. It seems that only even N nuclei can fission by thermal neutron. Is that correct?
Thermal neutron induced fission is a type of nuclear reaction where a thermal (or slow-moving) neutron is absorbed by a heavy atom, causing it to split into two or more smaller atoms, releasing a large amount of energy in the process.
The main conditions for thermal neutron induced fission are the presence of a heavy atom (such as uranium-235 or plutonium-239), a source of thermal neutrons, and a neutron moderator to slow down the neutrons to thermal energies.
The energy released in thermal neutron induced fission is significantly larger than other types of nuclear reactions, such as alpha decay or beta decay. This is because the fission process involves breaking apart a heavy atom, which has a much higher binding energy than the decay of a smaller atom.
Thermal neutron induced fission has several important applications, including nuclear power generation, nuclear weapons, and medical isotope production. It is also used in research and development of nuclear technologies and for analysis of materials using neutron activation.
In nuclear power plants, thermal neutron induced fission is carefully controlled using control rods, which absorb excess neutrons and slow down the rate of fission. This prevents the chain reaction from becoming uncontrollable and causing a nuclear meltdown. Additionally, nuclear reactors are designed with multiple safety systems to prevent accidents and mitigate any potential radiation releases.