P2.5 Nuclear fission and nuclear fusion

Question 1

What are sub-atomic particles?

Answer 1

Protons,neutrons and electrons

Question 2

What are nucleons?

Answer 2

The particles found in the nucleus

Question 3

What is the atomic number of an element?

Answer 3

The amount of protons it has

Question 4

What is another name for the mass number?

Answer 4

Nucleon number

Question 5

What is the nucleon number?

Answer 5

The total number of protons and neutrons in the nucleus

Question 6

What are isotopes?

Answer 6

The same element with a different number of neutrons but the same number of electrons

Question 7

What is an ion?

Answer 7

An atom that has lost or gained an electron/s

Question 8

How does an unstable nucleus become more stable?

Answer 8

It decays by losing energy when certain types of ionising radiation are emitted from the nucleus

Question 9

What are the three types of ionising radiation?

Answer 9

• alpha particles
• beta particles
• gamma rays

Question 10

Can you predict when a nucleus will decay?

Answer 10

No, it is a random process

Question 11

What are the subatomic particles of an alpha particle, and what is its charge?

Answer 11

It contains two neutrons and two protons but no electrons, so it has a charge of +2

Question 12

Why do alpha particles have a short penetration distance?

Answer 12

They lose energy quickly because they produce many ions when they are emitted from the nucleus at high speeds

Question 13

Why do beta particles have a longer penetration distance than alpha particles?

Answer 13

They are less ionising than alpha particles and so can penetrate further into matter as they don’t lose energy as quickly

Question 14

What speed to gamma rays travel at?

Answer 14

The speed of light

Question 15

Do gamma rays have an electrical charge?

Answer 15

No

Question 16

Why are gamma rays able to penetrate more substances than beta particles?

Answer 16

Gamma rays are ten times less ionising and so don’t lose as much energy

Question 17

What materials can stop gamma rays?

Answer 17

Lead and many metres of concrete

Question 18

What is the most ionising type of radiation?

Answer 18

Alpha particles

Question 19

What type of radiation has the longest penetration distance?

Answer 19

Gamma

Question 20

What are three types of nuclear reaction?

Answer 20

• radioactive decay
• nuclear fission
• nuclear fusion

Question 21

What is nuclear fission?

Answer 21

When a large unstable nucleus splits into two smaller daughter cells

Question 22

When does nuclear fission occur?

Answer 22

When a large unstable nucleus absorbs a neutron

Question 23

What is the product of nuclear fission?

Answer 23

Two daughter cells and three neutrons

Question 24

What two types of energy are released from nuclear fission?

Answer 24

Thermal and kinetic

Question 25

What is an uncontrolled nuclear chain reaction?

Answer 25

When the neutrons released from fission are absorbed back into the daughter cell, making it unstable so that it splits and releases three neutrons which can get absorbed into another daughter cell, causing the reaction to happen again and again

Question 26

How can a chain reaction be controlled?

Answer 26

Another material can be made to absorb some of the neutrons

Question 27

What type of reaction is used in a nuclear reactor?

Answer 27

A controlled nuclear chain reaction

Question 28

What is nuclear fusion?

Answer 28

The process of two small nuclei combining to make a larger one

Question 29

What do nuclear reactors do?

Answer 29

Transform nuclear energy into thermal energy using fission

Question 30

Where do nuclear reactors get nuclear energy from?

Answer 30

The nuclei of uranium and plutonium atoms

Question 31

Where are control rods placed in the reactor core?

Answer 31

Between the fuel rods

Question 32

How do you increase the rate of fission in a nuclear reactor?

Answer 32

You move the control rods out so that fewer neutrons are absorbed

Question 33

What happens when the control rods are fully lowered in the reactor core?

Answer 33

The chain reaction stops and the reactor shuts down

Question 34

Why is concrete shielding used in a nuclear reactor core?

Answer 34

To prevent radiation and stray neutrons from escaping

Question 35

What does a moderator do?

Answer 35

Slow down the neutrons emitted from fission

Question 36

How is thermal energy produced in a nuclear reactor transferred to electrical energy?

Answer 36

• thermal energy is transferred to a coolan which is pumped through a reactor
• the super-heated water is pumped through a “heat exchanger” which produces steam
• the steam drives a turbine, which turns a generator
• the generator transfers the kinetic energy to electrical energy

Question 37

What is radioactive waste made up of?

Answer 37

Radioactive daughter nuclei and isotopes

Question 38

What is the energy source of stars?

Answer 38

The fusion of hydrogen atoms combining to form helium

Question 39

What is electrostatic repulsion?

Answer 39

A force that pushes apart two particles with the same charges

Question 40

Why does fusion happen on the Sun?

Answer 40

The Sun has a very strong gravitational field, which creates very high densities of nuclei at its centre, which means nuclei are much more likely to collide

Question 41

How can nuclei overcome electrostatic repulsion?

Answer 41

By travelling fast enough to collide

Question 42

How can you increase the speed nuclei move at?

Answer 42

Increasing the temperature

Question 43

Why is fusion power not being used?

Answer 43

It is difficult to sustain the high temperature required for fusion which means no experimental reactors have produced more energy than they have put in