- #1
saleem
- 4
- 0
I have this question
Why U-235 is fissionable by thermal neutrons whereas U-238
requires E>1.4MeV
Thank you:
Why U-235 is fissionable by thermal neutrons whereas U-238
requires E>1.4MeV
Thank you:
neu said:235 is fissle as it's activation energy/fissile barrier, the energy required to cause irreversible deformation of the nucleus is very low.
If you look at the semi empirical mass formula the coulomb and surface area terms reduce and increase respectivly (like a harmonic oscillator) when a neutron is absorbed by the nucleus. If the energy is great enough the coulomb term dominates and causes an irreversible deformation which leads to break up of the nucleus.
the activation energy is the energy required to do this
Im studying this currently myself so apologies if I am saying what you already know
U-235 and U-238 are both isotopes of uranium, meaning they have the same number of protons but different numbers of neutrons. U-235 has 235 neutrons, while U-238 has 238 neutrons.
U-235 is fissionable by thermal neutrons because it has a lower critical energy threshold for fission compared to U-238. This means that it requires less energy to split the nucleus of U-235 compared to U-238.
Thermal neutrons are neutrons that have slowed down to a low energy level, usually through collisions with other particles. They have a higher probability of causing fission in U-235 compared to other types of neutrons.
U-238 is not fissionable by thermal neutrons because it has a higher critical energy threshold for fission compared to U-235. This means that it requires more energy to split the nucleus of U-238, making it less likely to undergo fission with thermal neutrons.
The fission of U-235 with thermal neutrons is significant because it is the process used in nuclear reactors to produce energy. By controlling the fission of U-235, we can generate heat which is then used to produce electricity. This discovery has greatly impacted the energy industry and has led to the development of nuclear technology.