Nuclear Radiation

Question 1

What is ionisation?

Answer 1

Ionisation is when an electron is knocked off an atom (or added to an atom) producing a positive (or negative) particle

Question 2

What are the features of alpha particles?

Answer 2

Two protons and two neutrons (a helium nucleus)
Travels a few cm in air
Absorbed by paper or skin

Question 3

What are the features of beta particles?

Answer 3

Fast moving electron
Travels many cm in air
Absorbed by a few mm of aluminium

Question 4

What are the features of gamma radiation?

Answer 4

Electromagnetic wave
Travels many km in air
Partially absorbed by lead

Question 5

Name 4 natural sources of radiation

Answer 5

Radon gas from rocks and soil (partially granite)
Gamma rays from the ground
Carbon and potassium in body (from our food)
Cosmic rays from outer space

Question 6

Name 3 artificial sources of radiation

Answer 6

Medical applications such as x-rays and radionuclides
Fallout feom weapons testing
Nuclear waste from power stations

Question 7

What is activity?

Answer 7

The number of radioactive decays per second, measured in Bequerels (Bq)

Question 8

What is half life?

Answer 8

The half life of a radioactive source is the time taken for its activity to reduce by half

Question 9

Describe the 3 medical applications of nuclear radiation

Answer 9

Diagnosis - Injection of a radioactive tracer drug that goes to a specific area of the body and is detected using a Gamma Camera. Tracers emit gamma radiation.
Treatment - Gamma radiation can be used to kill cancer cells from outside the body.
Disease prevention - Medical equipment can be sterilised by exposure to gamma radiation

Question 10

Describe some industrial applications of nuclear radiation

Answer 10

Radiation can be used to test welds without destroying them and find leaks in underground pipes. Some jobs expose workers to a higher dose of radiation than normal - these include miners and aircrew as well as nuclear power plants.

Question 11

Describe the 2 main methods of reducing risk of harm from radiation (SID)

Answer 11

Shielding, e.g. using a lead apron, storing sources in lead lined boxes
Increasing distance from the radioactive source, e.g. using tongs to handle sources

Question 12

What does the risk of harm from nuclear radiation depend on?

Answer 12

Absorbed dose
Type of radiation
Type of tissue
Time of exposure

Question 13

What is absorbed dose measured in?

Answer 13

Grays (Gy)

Question 14

What is equivalent dose measured in?

Answer 14

Sieverts (Sv)

Question 15

What is eqivalent dose rate measured in?

Answer 15

Sv s-1, Sv h-1 etc.

Question 16

What is nuclear fission?

Answer 16

Nuclear fission is when a heavy nucleus splits into two nuclei of smaller mass, releasing some neutrons and energy.

Question 17

Describe the two types of nuclear fission

Answer 17

Spontaneous fission - this is very rare and happens when a very large nucleus is unstable enough to split into fission products by itself
Induced fission - this is caused by bombarding the nucleus with a neutron

Question 18

Describe uncontrolled fission

Answer 18

Neutrons released in nuclear fission can cause fission in more nuclei, releasing more energy and more neutrons, which can cause further fission. This is a chain reaction.

Question 19

How do you get more power from a nuclear fission reaction?

Answer 19

The neutrons released by the fission reaction are fast moving. A MODERATOR (e.g. graphite) is used to slow them down and INCREASE the chance of further fission reactions happening

Question 20

How do you control the power from a nuclear fission reaction?

Answer 20

The reaction is managed using CONTROL RODS (e.g. boron) which absorb some of the slow neutrons

Question 21

Describe nuclear fusion

Answer 21

Nuclear fusion is where two or more nuclei combine to form an element with a higher mass. This is the opposite of nuclear fission, but energy is still released in the reaction. Fusion takes place in the Sun and other stars.

Question 22

How does a nuclear power station work?

Answer 22

The heat released by the nuclear reaction is used to produce steam in the heat exchanger. The steam is used to turn a turbine, which then turns a generator, producing electrical energy.

Question 23

What are the advantages of nuclear power?

Answer 23

Nuclear power stations produce a large amount of energy for a small amount of fuel.
There are no carbon dioxide or sulphur dioxide emissions from a nuclear power station.

Question 24

What are the disadvantages of nuclear power?

Answer 24

Nuclear waste must be stored securely for a very long time.

Many people have a negative view of nuclear fuel.