P2.6 - Nuclear Fusion and Fission Flashcards
What are the two fissionable substances used in nuclear reactors?
Uranium-235 and Plutonium-239
What is nuclear FISSION?
The splitting of an atomic nucleus.
What must the nucleus absorb for nuclear fission to happen?
A neutron.
What happens to the nucleus undergoing fission?
It splits into two smaller nuclei and two or three neutrons. Energy is released.
What can the released neutrons go on to start?
A chain reaction.
What is nuclear FUSION?
The joining of two atomic nuclei to form a larger one.
What astronomical process uses nuclear fusion?
Energy release in a star.
How do stars begin to form?
When enough dust and gas from space
is pulled together by gravitational attraction. Smaller
masses may also form and be attracted by a
larger mass to become planets.
What happens during to ‘main sequence’ of a star’s lifetime?
The forces within it are balanced, so it is stable.
What stages do stars about the same size as the sun go through after the main sequence?
Red Giant —> White Dwarf —> Black Dwarf
What stages do stars much bigger than the sun go through after the main sequence?
Red Super Giant —> Supernova —> Black Hole/Neutron Star
What elements are formed during a star’s stable period?
Elements up to iron.
What elements are formed during the supernova?
Elements heavier then iron.
What does fusion need to happen?
Heat and pressure,
How is Helium formed in a star?
Hydrogen Nuclei fuse together to form Helium Nuclei.
