Mod-01 Lec-36 Nuclear Energy Programme of India

So, in the previous lecture we talked about the fate of neutrons in a nuclear reactor. You remember the design, you have fuel core which contains the fissile material and it is surrounded by moderators, the fuel rods are separated by the moderators in the reactor core. And once you have some thermal neutrons ready to fission; what happens to them that

we discussed last time, just to remind you can look at the screen on which it is there. So, you have these n thermal neutrons in the fuel ready to cause fission. And of them some are radiative captured they are absorbed and they do not cause fission. Those which cause fission create more fast neutrons back factor we write as this eta. So, here it is so from

n it is n times eta fast neutrons. Then you these some of these fast neutrons can also cause fission because of uranium 238. And that gives you this extra factor of epsilon. So, eta times epsilon then of these neutrons which go to the moderator some of them encounter the uranium 238 fuel rod surface. And they can get captured their through those resonance

reactions. And therefore which are finally thermalized is here a factor p. And after thermalization also they keep moving in the moderator for quite some time and during that time they can interact with the moderator material itself. Some nuclear reactions can go in the moderator, and another factor f is converted is multiplied to get you slow

neutrons in the fuel rods once again. So, this is 1 complete generation or 1 complete cycle. So, in 1 generation; if you have these n thermal neutrons the next generation here you have these n eta epsilon p f thermal neutron. So, from 1 generation to the next generation the number of thermal neutrons in the fuel rod is multiplied by eta times epsilon times