Nuclear fission

spideyinspace

stars have million kelvin temperature because of fusion..if fusion can produce this much temperature then why cant the fission produce million kelvin temperature...am confussed..

malawi_glenn

Fission and fusion if two totaly sperate things.

Fission you split a nucleu and due to the relased binding energy parts fly away and heat the rod (heat is motion/vibration, when nucleis are split, the fragments are beeing breaked in the rod, and that makes heat) and the rod will heat the water. As a water boiler, you have a metal rod, which gets warm, like 500K, and that makes the water boil.

The stars are hot in its interior due to huge gas compression due to gravitational collapse. And in order to overcome the coloumb barrier (two similar charges repel each other), lots of energy/velocity of the protons is needed. So in order do have many partilces(protons) undergo fusion is to have high heat (heat is average velocity/kinetic energy of particles). So in stars, the temperature from grav-collapse (the gas law tells you that if you compress gas, temp will rise) can make the hydrogen ions (protons) undergo fusion, wich releases energy (photons) that can halt the gas from beeing gravitationally collapsed into a degenerate remnant or black hole. The sun is 15millions kelivn in the center and 6000K on the "surface".

But on earth, we cant have a big thing like the sun on earth, and if you have 15million K in a container... things melt... (melt at approx 6000K so we cant even reach 15million K in an ordinary container). So one uses strong magnetic fields, you know that charges in motion in magnetic fields are bent. So you contain this hot hot plasma in magnetiv cages on earth.

I dont have time to give you a more lengthy answer than this, I suggest you wait for more people to reply or either (better) consult textbooks from your library in introductory nuclear physics and stellar physics.

spideyinspace

is it possible atleast theoritically to bombard a lighter nuclues than uranium and having Atomic number >60 if we use a very high energy neutron...so that there wont be any need for uranium in future if this is possible...

malawi_glenn

I dont know if nucleis with so low mass-number is instable due to neutron fission. And it also depends of you want to use thermal neutrons or higher energy neutrons, or maybe even have protons as probes.

Anyway, i know research is going on to have a Thorium isotope instead of Uranium, there is much more thorium in the world + it dont give long lived daugther nucleids which are radioactive. Also transmutation of "burned out" uranium is under research. There is a lot of info if you google. And Astronuc is a guru about these things.

But I am very sure that we will get fusion working before uranium runs out. But still, we need to take care of the Uranium-waste. My opinion.

spideyinspace

Thank you for all replies..