Fission and fusion Flashcards
What is a chain reaction
neutrons released in fission can be absorbed by other nuclei
These nuclei split (fission)
Fission releases more neutrons
neutrons in fission can be absorbed by other nuclei
what is fission
large nuclei break up to form smaller nuclei and release energy
where is fusion used
Nuclear power stations
Submarines
what is fusion
small nuclei fuse to form a larger nucleus.
Fusion reactions release energy inside stars
where is fusion used
Release energy in stars
what is radioactive decay
the process in which an unstable nucleus loses energy by emitting ionising particles and radiation
how does Uranium -235 split (process of fission)
An incident Neutron collides with the parent nucleus making it unstable
the nucleus splits (fission)
Energy is released as kinetic energy of the fission products
what are the products of uranium-235
-2 radioactive daughter nuclei smaller nuclei that are not always identical to each other.
-A small number of neutrons
- The combined atomic mass of daughters and neutrons must equal the parent
what is the role of the control rods
-Control rods absorb the neutrons
-increases or decreases the rate of fission
-control rods can be moved in and out of the reactor
-makes more or fewer neutrons available
what is the role of a graphite core
Neutrons in the moderator are slowed down
Increasing the rate of fission
what is the role of shielding
Reactor vessels are made of steel and surrounded by a layer of concrete about 5meteres thick.
this prevents any radiation escaping, even neutrons
what increases the rate of fission
slowing down the neutrons
what is the difference between fusion and fission
fusion is the process which two smaller nuclei being forced together to form a heavier nucleus
- this is the energy source for stars
-fusion cannot happen at low temperatures or pressures
-fusion is very hard to make a practical and economic fusion power station
Fission is the process which a large nuclei splits to form two smaller nuclei after absorbing neutrons which release more neutrons.
- this energy source for nuclear power stations
- fission can happen at low temperature and pressures
why does nuclear fusion does not happen at low temperatures and pressure
due to electrostatic repulsion of protons
- the faster the particles are the closer they will get to each other before repelling
what conditions does fusion need
Very high temperatures – kinetic energy (move faster — more collisions)
very high pressures
very high Kinetic energy
