OCR Gateway Science Additional B Higher P4- Fission and fusion

When does nuclear fission occur?

When a large unstable nucleus is split up and energy is released as heat

What is a chain reaction?

When a neutron is absorbed by the nucleus of a uranium 235 atom and the nucleus is less stable than before and it splits into two parts releasing energy. Several neutrons produced in this process and go on to strike the nuclei of other atoms and causing more fission.

What happens if a nuclear chain reaction is uncontrolled?

Nuclear explosion.

What type of uranium is used in nuclear power stations?

Enriched uranium is used that contains a bigger proportion of uranium 235 isotope than occurs naturally

When does the chain reaction start?

When the first uranium nucleus splits

How do graphite moderator core between the fuel rods control fission?

Slows down fast moving neutrons that are more likely to be captured by uranium nuclei- it makes them too slow to be absorbed by uranium nuclei

How does boron rods control fission?

Absorb neutrons to slow down chain reaction. Can be put in to slow a fast chain reaction and can be taken out to speed up a slow chain reaction

How is electricity generated at a nuclear power station?

Uranium 235 is bombarded with neutrons to undergo a chain reaction which causes it to split releasing thermal energy and more neutrons to strike other uranium atoms to release more thermal energy. Thermal energy produced by fission boils up water to turn to steam which causes the turbine to turn which causes the generator to turn which makes electricity which goes to step down…