Nuclear Decay and Nuclear Energy

Question 1

What is Nuclear Fission?

Answer 1

Fission is the splitting of a heavy nucleus into 2 lighter nuclei- a lot of energy is released in this process.

Question 2

What is the process of Fission?

Answer 2

1) A slow moving neutron collides with a heavy nucleus (Usually Uranium-235)
2) The extra neutron makes the nucleolus unstable and it starts to oscillate.
3) The heavy Uranium nucleolus splits into Kr82/36 (Krypton) and Ba144/56 (Barium)
4) This releases Kr, Ba, gamma rays, energy and 3 fast moving neutrons
5) Once slowed down by moderators these 3 new neutrons can interact with more nucleus and cause a chain reaction.

Question 3

How is a fission reaction controlled in a nuclear reactor?

Answer 3

Boron control Rods- can be raised or lowered into the reactor. When lowered, they absorb the 2 extra neutrons so the reaction is stable which prevents a chain reaction.

Graphite moderators- Slows the neutrons down so they can be absorbed by Uranium Nuclei and the reaction can persist.

Concreate shield- Reduces the radiation that can escape from inside the reactor.

Question 4

How do we get energy out of Nuclear Fission

Answer 4

The heat from the reaction turns water into high pressure steam that drives turbines.

Question 5

What is nuclear Fusion?

Answer 5

This is when two small nuclei (2/1H and 3/1H) are fused together to create one large nucleolus. This releases more energy than fission and a neutron. However, there is a lot of energy required to overcome the repulsion between the two positive nuclei. At the moment, there is a net negative energy output.

Question 6

What is the process of Fusion?

Answer 6

1) Two hydrogen isotopes (Deuterium (2/1) and Tritium (3/1)) are super-heated until they become an ionised gas (Plasma) which allows the atoms to overcome repulsive forces.
2) The two isotopes then fuse together, releasing 7x the amount of energy as fission.
3) There is also 1 He (Helium 4/2) atom and 1 neutron released

Question 7

What does the nucleon number tell us?

Answer 7

The amount of protons and neutrons in a nucleolus of an atom (or ion).

Question 8

What are the 2 isotopes in fusion?

Answer 8

Deuterium (2/1 Hydrogen)

Tritium (3/1 Hydrogen)

Question 9

What is a alpha particle?

Answer 9

A helium atom without electrons

4/2

Question 10

What are the examples of low level waste?

Answer 10

Contaminated equipment, materials and protective equipment

Question 11

What are the examples of intermediate level waste?

Answer 11

• Components from nuclear reactors

- radioactive sources used in medicine or research

Question 12

What are the examples of high level waste?

Answer 12

Used nuclear fuel

Chemicals from reprocessing fuels

Question 13

How do we dispose of low level waste?

Answer 13

Place it in drums surrounded by concrete, and in clay-lined landfill sites

Question 14

How do we dispose of indermediate level waste?

Answer 14

Mixed with concrete and put in a stainless steel drum in a purpose-built store

Question 15

What is the process of disposing high level waste?

Answer 15

1) Stored in underwater pools for 20 years
2) Placed in storages casks in purpose-built underground stored where circulating air removed heat produced
3) Decays into intermediate level waste over THOUSANDS of years

Question 16

What is the purpose of the graphite moderators?

Answer 16

They slow down the neutrons and make it easier for the uranium to absorb the neutron and become unstable.

Question 17

What is nuclear fission?

Answer 17

The breaking apart of an unstable, usually heavy, nuclei. This produces a lot of energy.

Question 18

What is nuclear fusion?

Answer 18

The joining together of two light nuclei. This produces a lot of energy.

Question 19

What is the purpose of the boron control rods?

Answer 19

The absorb some on the neutron (ideally 2 of the 3) released from fission which controls the reaction and prevents a chain reaction.

Question 20

Why are fusion reactors on Earth difficult to control?

Answer 20

It needs to contain the high temperature plasma and the neutron radiation?

Question 21

How are fusion reactions contained?

Answer 21

• Encased in a concrete shield to stop neutron radiation from escaping
• Very temperature resistant materials to withstand high temperatures
• Strong containments due to high pressured ionised hydrogen gas.

Question 22

What are the advantages and disadvantages of using fission to generate power?

Answer 22

Advantages

• Already developed and proven concept
• Has a net positive energy output
• Produces a lot of energy (not as much as fusion)

Disadvantages

• Nuclei produced are radioactive and need to be stored safely
• Requires control rods and moderators to sustain and control the chain reaction.
• Uranium fuel is running out

Question 23

What are the advantages and disadvantages of using fusion to generate power?

Answer 23

Advantages

• Fusion produces 7x more energy per kg that fission
• Deuterium and tritium are plentiful
• Tritium has a much shorter half-life compared to fission waste (Ba and Kr). Helium produced is stable too.

Disadvantages

• Still in research phase and not commercially viable
• Requires a high temperature and pressure
• Net negative energy output for the moment