Fission and Fusion

Question 1

What are the three nuclear reactions which release large amounts of energy?

Answer 1

• Nuclear fission
• Nuclear fusion
• Radioactive decay

Question 2

What is the process of nuclear fission?

Get it all right

Answer 2

• Fission is the splitting apart of a large nuclei into two or more smaller nuclei
• A neutron collides into a uranium 235-nucleus, creating a uranium-236 nucleus which is highly unstable
• This U-236 nucleus splits into two daughter nuclei, as well as two or more neutrons
• The neutrons released can collide into other uranium-235 nuclei, forming an endless chain reaction until all of the fuel is used up
• Energy is released in the form of kinetic energy from the fast moving daughter nuclei

• Plutonium can also be used
• Gamma rays are also emitted

Question 3

What are the purposes of control rods in nuclear reactors?

Answer 3

They absorb excess neutrons and control the rate of reaction by inserting them in and out

Control rods are made of boron

Question 4

What are the purposes of moderators in nuclear reactors?

Answer 4

They slow the neutrons so they can be absorbed by U-235 nuclei within the fuel rods, which increases the rate of reaction

Moderators are made of graphite

Question 5

What is the purpose of shielding around nuclear reactors?

Answer 5

It absorbs dangerous radiation emitted by the radioactive daughter nuclei

Shielding is made out of steel, concrete or lead

Question 6

How is power made within a nuclear fission reactor?

Answer 6

• The fission products move at a very fast speed which is transferred into kinetic energy
• This heats the coolant water, which creates steam which spins a turbine, powering a generator, creating electrical energy

Question 7

What is the process of nuclear fusion?

Answer 7

• Fusion is the joining together of two smaller nuclei to form a larger nucleus
• Two hydrogen atoms, usually tritium and deuterium are fused together to form a helium nuclei and a neutron
• The mass of the products are less than the mass of the reactants, so lots of energy is released due to the lost mass being converted into energy

Question 8

Where does nuclear fusion occur naturally?

Answer 8

Stars (like the sun)

It is their energy source

Question 9

What are the conditions needed for fusion?

Answer 9

• Extremely high temperatures
• Extremely high pressures

Basically the conditions of a star. Becuase these conditions are needed, it is hard for it to take place on earth feasibly

Question 10

Why are the conditions needed for fusion needed?

Answer 10

• The two hydrogen nuclei are positively charged, so there are extremely strong electrostatic forces of repulsion between the two nuclei which need alot of energy to overcome
• To overcome these forces, they must have very high levels of kinetic energy so they can travel at very high speeds so they can get close enough to be able to fuse
• Very high temperatures must be present to provide this kinetic energy
• High pressures are also needed to increase the number of successful collisions and move the nuclei close enough together