Atoms and Nuclear Radiation

Question 1

Why do unstable nuclei give out radiation?

Answer 1

Unstable nuclei undergo decay to become more stable
As they release radiation their stability increases

Question 2

Define the activity

Answer 2

Activity is the rate of decay of a source of unstable nuclei.

Question 3

What is the unit of radioactive activity?

Answer 3

Becquerel (Bq)

Question 4

What is count rate?

Answer 4

The number of radioactive decays per second for a radioactive source

Question 5

Give an example of a detector that may be used to measure the count rate.

Answer 5

Geiger-Muller tube

Question 6

What are the types of radiation?

Answer 6

Alpha
Beta
Gamma

Question 7

What is an alpha particle made up of?

Answer 7

Two protons and two neutrons (It is the same as a helium nucleus)

Question 8

What is the range of an alpha particle through air?

Answer 8

A few centimetres

Question 9

What stops an alpha particle?

Answer 9

A sheet of paper

Question 10

What is the ionizing power of an alpha particle?

Answer 10

High ionizing power

Question 11

What is a beta particle?

Answer 11

A fast-moving electron

Question 12

What is the range of a beta particle?

Answer 12

Few metres

Question 13

What will stop a beta particle?

Answer 13

A sheet of aluminum

Question 14

What is the ionizing power of a beta particle?

Answer 14

Moderate ionizing power

Question 15

What is gamma radiation?

Answer 15

A high-energy electromagnetic wave

Question 16

What is the range of gamma radiation?

Answer 16

Very far distances (almost infinite)

Question 17

What will stop gamma radiation?

Answer 17

Thick layers of lead or concrete

Question 18

What is the ionizing power of gamma radiation?

Answer 18

Low ionizing power

Question 19

Describe the nature of radioactive decay

Answer 19

● Random
● Which nuclei decays and when is
determined only by chance
● It is impossible to predict which nuclei
will decay and when

Question 20

Define the half-life of a radioactive isotope

Answer 20

The time it takes for the number of unstable nuclei in a substance to halve

Question 21

What is radioactive contamination?

Answer 21

The presence of unwanted radioactive nuclei on other materials

Question 22

What is irradiation?

Answer 22

The process of exposing a material to nuclear radiation

Question 23

Give 4 sources of background radiation

Answer 23

1. Rocks
2. Cosmic rays from space
3. Nuclear weapon testing
4. Nuclear accidents

Question 24

What factor determines how dangerous a particular radioactive isotope is?

Answer 24

The half-life of the isotope

Question 25

Why are isotopes with long half-lives particularly harmful?

Answer 25

They remain radioactive for much longer periods of time

Question 26

State two uses of nuclear radiation in the field of medicine

Answer 26

Examining of internal organs
Controlling and destroying unwanted tissue

Question 27

How is radiation used in sterilisation?

Answer 27

Gamma emitters are used to kill bacteria/parasites on equipment.

Question 28

Explain the process of radiotherapy

Answer 28

Gamma emitters direct gamma rays at the cancerous cells
The cancerous cells absorb the radiation and are killed

Question 29

How are medical tracers chosen?

Answer 29

They should have a short half life and decay into a stable isotope.
They should only release gamma radiation since it is weakly ionising and can easily pass through body tissue without damaging it.

Question 30

What is nuclear fission?

Answer 30

The splitting of large, unstable nuclei to form smaller more stable nuclei (+the emission of spare neutrons)

Question 31

Give an example of a fissionable isotope

Answer 31

Uranium - 235

Question 32

What usually needs to happen to induce fission?

Answer 32

The unstable nuclei must absorb a neutron

Question 33

Alongside two smaller nuclei, what else is emitted in a fission reaction?

Answer 33

●Two or three neutrons
● Gamma rays
● Energy

Question 34

What takes place during a chain reaction in a nuclear reactor?

Answer 34

●An unstable nucleus absorbs a neutron
● The nucleus undergoes fission and releases 2 or 3 further neutrons
● These induce more fission, which results in a chain reaction

Question 35

What is the consequence of an uncontrolled chain reaction?

Answer 35

The rate of fission events becomes to high and results in the production of
too much energy
This can lead to a nuclear explosion

Question 36

What are the three main components of the core a nuclear reactor?

Answer 36

1. Fuel rods
2. Control rods
3. Moderator

Question 37

What is the role of the moderator in a nuclear reactor?

Answer 37

To slow down the neutrons so they are travelling at speeds which allow them to be absorbed by fissile nuclei and cause fission.

Question 38

How is the chain reaction in a fission reactor kept under control?

Answer 38

●Control rods are positioned in between the fuel rods
● The rate of fission is controlled by moving these rods up and down
● The lower the rods are inserted, the slower the rate of fission

Question 39

What is nuclear fusion?

Answer 39

The joining of two light nuclei to produce a heavier nuclei and release energy

Question 40

Explain the difficulty of generating energy through nuclear fusion

Answer 40

Fusion requires very high temperatures which in itself requires large quantities of energy and also requires casing which can withstand them

Question 41

Explain why nuclear fusion is currently not a viable way to produce energy on Earth

Answer 41

With current equipment/techniques, the energy required is greater than the energy produced, resulting in a net energy loss