Is that good enough?
Note Plutonium can be used and was in the first weaponry of this type. It however to more force to displace I believe the non enriched material. It was actually more stable… I could be wrong in this and be backwards on this.
I am well dyslexic however plutonium is found naturally in the earth however we do have some different types of the element that agains deals with electron levels in this state as well. This is the level of fuel that it can product or provide over time period or combustion energy.