P7.7 - Nuclear Fission (Finished) Flashcards
What is nuclear fission?
Nuclear fission is the splitting of an atom’s nucleus into two smaller nuclei releasing energy in the process
What does a nucleus release when it undergoes fission?
- Two or three neutrons at high speeds
- Energy, in the form of gamma radiation (also kinetic in particles)
What has to be done for nuclear fission to occur?
Usually the nucleus has to absorb a neutron for fission to occur, however very rarely spontaneous fission could occur
Why is a chain reaction of fission events produced usually?
When a nucleus undergoes fission it releases several neutrons which can be absorbed by more nuclei causing them to split and so on forming a chain reaction
What happens to a nuclei during fission?
1) An unstable fissionable isotope is hit by a neutron
2) it splits to form two new lighter elements of roughly the same size
3) Two or three neutrons are also released along with energy in the form of gamma rays
How is the energy from fission carried away kinetically?
Energy from a fission reaction is partly carried away in the kinetic energy stores of the remaining free neutrons and other decay products
How is energy collected in a nuclear reactor?
The energy carried away after fission by gamma rays and the kinetic energy if particles is used to heat water to make steam to turn turbines
The amount of energy in a nuclear reactor is controlled by changing ___
How quickly the chain reaction can occur
How is how quickly the chain reaction in a nuclear reactor can occur changed?
Controll rods can be lowered / raised inside the nuclear reactor to absorb neutrons slowing down the rate of the chain reaction
What is used inside a nuclear reactor?
U235 is the fissionable isotope used in nuclear reactors. It makes up 2-3% of the fuel, the rest is U238
What does U235 produce when split?
U235 produces two neutrons, Kr and Ba when it undergoes fission
