Nuclear Energy

Question 1

What is nuclear energy?

Answer 1

Energy that originates from the nuclei of atoms.

Question 2

What three types of reactions release nuclear energy?

Answer 2

• Radiation from nuclei (in the form of alpha, beta and gamma particles)
• Nuclear fission (from the splitting of a nucleus)
• Nuclear fusion (from the fusing of two nuclei)

Question 3

What is nuclear fission?

Answer 3

The splitting of a large nucleus into two similar smaller nuclei with the release of neutrons and energy.

Question 4

What is a chain reaction?

Answer 4

Fission creation in which at least one neutron is emitted in order to carry on the reaction.

Question 5

What is the critical mass?

Answer 5

The minimum amount of fissile material required in order to sustain a chain reaction.

Question 6

Explain how U-235 (uranium isotope) undergoes fission.

Answer 6

• A sufficient mass of uranium is brought together
• When a neutron strikes the U-235, it briefly turns into U-236. This is very unstable and will quickly undergo fission.
• The U-236 splits into krypton (Kr) and barium (Ba), along with three neutrons
• The neutrons carry most of the kinetic energy from the fission
• Each of these neutrons can cause a chain reaction which carries on automatically until it is slowed or stopped by human interaction

Question 7

What does the critical mass of an isotope depend on?

Answer 7

• Density
• Temperature
• Shape
• Purity

Question 8

What is radiative capture?

Answer 8

When a nucleus captures/absorbs a fast moving neutron.

Question 9

Name the parts of a nuclear reactor. (7)

Answer 9

• Fuel rods
• Control rods
• Moderator
• Heat exchanger
• Pipes
• Turbines
• Shielding

Question 10

What is the purpose of fuel rods?

Answer 10

The uranium fuel rods (which have a higher percentage of U-235) are used as the fissile material.

Question 11

What is the purpose of control rods?

Answer 11

They are used around the fuel rods to absorb neutrons being emitted from the fuel rods. They are raised proportionally to control the chain reactions.

Question 12

What is the purpose of the moderator?

Answer 12

It slows down fast neutrons and prevent radiative capture from happening.

Question 13

What is the purpose of the heat exchanger?

Answer 13

The coolant carries the excess heat to the heat exchanger.

Question 14

What is the purpose of pipes?

Answer 14

The cold water moves in sealed pipes through the heat exchanger and os converted to steam by the coolant energy.

Question 15

What is the purpose of turbines?

Answer 15

They generate electricity.

Question 16

What is the purpose of shielding?

Answer 16

It prevents radiation leaks.

Question 17

State the advantages of nuclear fission power.

Answer 17

• Doesn’t emit greenhouse gases
• It produces massive amounts of energy very economically
• There will be no shortage pf nuclear fuel
• Reduces the need for fossil fuels
• Reactors can be used to create new elements for research and development
• Very low accident rate compared to other energy sources

Question 18

State the disadvantages of nuclear fission power.

Answer 18

• Radioactive waste has a very long half-life and is expensive to store
• Reprocessing of fuel is hazardous and expensive
• If a major accident occurs there can be a large scale health hazard

Question 19

What is nuclear fusion?

Answer 19

The joining of two small nuclei to create a larger single nucleus, with the release of energy.

Question 20

What are the factors affecting fusion?

Answer 20

• Pressure
• Temperature
  These are required in extreme amounts to overcome the repulsive coulomb force

Question 21

What are the advantages of nuclear fusion?

Answer 21

• Little or no radioactive or harmful by-products are produced
• Significantly higher amounts of energy are released than any current technology
• The fuel required for fusion is relatively cheap and plentiful

Question 22

What are the disadvantages of nuclear fusion?

Answer 22

There are no major disadvantages to speak of other than the difficulty in sustaining the reaction.

Question 23

State some precautions for dealing with radiation.

Answer 23

• Reduce exposure to radiation as much as possible
• Increase shielding on radioactive isotopes and radioactive waste
• Warn the public about potential hazards
• Always wear protective clothing and do not smoke, eat or drink near ionising sources

Question 24

What is background radiation?

Answer 24

Radiation from cosmic rays, the Earth’s crust and other radioisotopes

Question 25

How would you measure background radiation?

Answer 25

Using a G-M tube take a count of 5 minutes. Divide the count by the time. Repeat and get an average.

Question 26

What is radon?

Answer 26

It is a product of radium. Granite is a primary source of radium gas, which seeps out from the soil and into buildings. If it is present in high enough concentrations, it can lead to serious lung problems and cancer. This can be prevented by diluting the radon. This can be done by keeping good ventilation in buildings or installing radon traps or barriers.