Paper 1 - nuclear Fusion / Fission

Question 1

What is nuclear fission ? and what is the energy used for ?

Answer 1

In a nuclear fission reaction a large unstable uncleus splits into two smaller ones, releasing large amounts if energy, used to heat water in power stations.

Question 2

Nuclear fission of uranium-235 - what does it produce ?

Answer 2

Nucleus splits up when it absorbs a neutron. The fission of uranium 235 produces two daughter nuclei, two or more neutrons and also releases energy. -> daughter nuclei radioactive

Question 3

What happens to the neutrons in a nuclear fission reaction ?

Answer 3

In a controlled chain reaction two of the neurons are absorbed by other materials. Only one neutron from each fission can cause other fission

Question 4

What happens if a chain reaction is not properly controlled ?

Answer 4

💥There will be a nuclear explosion 💥

Question 5

What occurs during a chain reaction ?

Answer 5

The neurons released by the fission of U - 235 may be absorbed by other nuclei, each of which may undergo fission and produce more neurons - chain reaction.

Question 6

How can a chain reaction be controlled to avoid explosion.

Answer 6

By using different material to absorb some of the neutrons. This slows down the reaction because there are fewer neutrons to cause more nuclei to undergo fission

Question 7

What is nuclear fusion ?

Answer 7

Nuclear fusion involves the joining of smaller nuclei to form larger nuclei releases large amounts of energy.

Question 8

Fusion and stars. How is energy released?

Answer 8

• During a star’s life, vast quantities of hydrogen nuclei are converted to helium nuclei by nuclear fusion - source of energy for stars.
• Over time heavier elements produced (deuterium, tritium and helium) and star will eventually die - billions of years
• The mass of the product is slightly less than the mass of the reactants. Mass difference released as energy in the form of thermal energy.
• Takes place under very high pressure and temp in stars. Enormous temps and pressure allowed the charged nuclei to overcome the repulsive electrostatic forces between nuclei.

Question 9

What are the difficulties of nuclear fusion ?

Answer 9

• nuclei need to get very close before fusion can happen. Under normal conditions the positive charges on nuclei repel each other (ELECTROSTATIC REPULSION) only at high temps and pressure are the nuclei moving fast enough to overcome the repulsion.
• high temperature and pressure hard to replicate in fusion power stations and end up using more energy than is produced !

Question 10

Out of fission and fusion, which Is more beneficial ?

Answer 10

Obtaining a continuous amount of energy is much harder to do using nuclear fusion than fission reactions.

Question 11

How do nuclear fusion and fission compare ?

Answer 11

Initial neutron moves slow compared to nuclear fusion