Are nuclear chain reactions ever possible?

Question

What are the circumstances/requirements for the nuclear chain reaction to occur?

Also... Why would there be a subcritical mass of a fissile isotope?

Answer 1

Yes , look at the sun

Answer 2

as far as is ordinary, nuclear fission explosions are the end results of a thoroughly man made technique. with a view to have such an explosion the ingredient Uranium would desire to be separated into its ingredient isotopes. a variety of isotopes is radioactive Uranium U235 which contains in basic terms a small fraction of ther ingredient... maximum of it being the non-radioactive U238. This operation is quite high priced and demands an incredible array of equipment. considering the fact that nature operates in accordance to the assumption of dispersement and rot, that's the reason we stumble on each and every of the isotopes mixed mutually quite than being separated. there is as a result no ordinary organic technique which will separate the isotopes of any elemnet, no longer to show Uranium. whilst it comes to nuclear FUSION explosions the region is reversed so as that we frequently see stars exploding.

Answer 3

yes