Mod-01 Lec-35 Nuclear Fission Reactor

So, we discussed the basic reactions in neutron induced fission of uranium. Natural uranium has 2 isotopes; uranium 235 and 238; little bit of uranium 233 also. And, we saw how a neutron when gets into uranium 235. It can induce almost instantaneous fission in the time scale of 10 to the power minus 15, 16 seconds. And, we call it fissile material

235 uranium is a fissile material. It can fission on absorbing thermal neutron low-energy neutron. The other component uranium 238 which is much larger abundance in natural uranium that is not fissile. If you put neutron into it most likely low-energy neutrons will not create a fission in it. So, today we will be talking about general

features or basic basics of nuclear fission reactors which are used for power generation from nuclear fission. All over the world including India large number of fission reactors are operating; in which one produces power from this nuclear fission and uses it for various purposes. Before going into that description of typical fission reactor let me little bit

discuss more about the reactions of neutron with uranium. We have already seen the nuclear reactions with uranium 235 and 238 cross-sections. How much is the cross-section of this induced fission? So, that is one thing we will be doing. So, neutron and then uranium 235 this goes to uranium 236 in excited state and that fission

in 2 parts. So, the cross-section and then plus energy and some neutrons and so on. So, the cross-section for probability for this reaction depends very strongly on energy of this incoming neutron. At almost 0 energy, when it comes you know that the excitation energy is higher than the activation energy of that fission barrier and it takes place.