U-238

[granpa]

U-238 is common but it is non-fissile.

 

Uranium-238 (238U or U-238) is the most common isotope of uranium found in nature, with a relative abundance of 99%. Unlike uranium-235 it is non-fissile, which means it cannot sustain a chain reaction. However, it is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239. 238U cannot support a chain reaction because inelastic scattering reduces neutron energy below the range where fast fission of one or more next-generation nuclei is probable.

 

 

Question: if uranium atoms were 3 times smaller would U-238 still be non-fissile?

[Vmedvil]

That would mean that the SNF was 3 times stronger, nope, that would mean that it would be less fissionable, hell, if the SNF was that strong then even U -235 would not be fissionable, you would need a even larger atom to create fission and also there would be more elements on the periodic table.  

Edited September 30, 2017 by Vmedvil