4th - Fission And Fusion Flashcards
Products of nuclear fission
- 2 daughter nuclei (smaller, not always identical to each other)
- small no. Of neutrons
- release energy
(Combined atomic mass of daughters and neutrons = parent atomic mass).
Where are fission reactions used
Nuclear power stations
Submarines
Process of nuclear fission
- Neutron collides with parent nucleus = unstable
- nucleus splits
- energy released as kinetic energy
What is radioactive decay
When an
- unstable nucleus loses energy
- by emitting ionising particles and radiation
What is nuclear fusion
- two small nuclei fuse to form a larger nucleus
- release energy inside stars (energy source)
- unable to generate enough energy on earth
How does a chain reaction occur?
- Neutrons released in fission reaction can be absorbed by other nuclei
- nuclei split and release more neutrons
- these neutrons can be absorbed by other nuclei - and so on
What does the graphite core act as
A moderator
What does the graphite core moderator do
- neutrons are slowed down
- increasing the rate of fission
What do control rods do
- absorb neutrons
- increases or decreases the rate of fission
What are reactor vessels made of
Steel
What is shielding made of
Concrete
What does shielding do
- Thick Layer of concrete
- prevents any radiation or neutrons escaping
Differences between nuclear fusion and fission
Fusion
- energy source for stars
-can’t happen at low temps or pressures.
- very difficult to make a fusion power station
Fission
- energy source for nuclear power stations
- can happen at low temps or pressures
What do positive charges do
Repel each other - electrostatic repulsion
What benefit does the speed of the particles have for attraction
The faster the particles are, the closer they will get to each other before repelling
What are the conditions fusion needs to occur
- very high pressure
- very high temperature
- very high kinetic energy
Why does fusion need such high conditions to occur
To overcome electrostatic repulsion
They increase rate of collisions, which increases rate of fusion
