7.2.1-7.2.5 - Radioactivity, Uses and Danger

Question 1

What are objects called that contain radioactive nuclei?

Answer 1

Objects containing radioactive nuclei are called sources of radiation

Question 2

What is the activity which radiation decays at defined as?

Answer 2

The rate at which the unstable nuclei from a source of radiation decays

Question 3

What is radiation measured in?

Answer 3

Activity is measured in Becquerels the symbol is BQ.1 Becquerel is equal to 1 nucleus in the source decaying in 1 second

Question 4

How does the activity of a source decrease?

Answer 4

The activity of a source decreases with time
This is because each decay event reduces the overall number of radioactive particles in the source
The nature of radioactive decay can be demonstrated by observing the count rate of a source using a Geiger-Muller (GM) tube, and then plotting these results against time
These fluctuations in count rate on the GM tube also provide evidence for the randomness of radioactive decay

Question 5

What is half life?

Answer 5

The time it takes for the number of nuclei of a sample of radioactive isotopes to decrease by half

Question 6

How is half life measured?

Answer 6

Measure the initial activity, A0, of the sample
Determine the half-life of this original activity
Measure how the activity changes with time
The time taken for the activity to decrease to half its original value is the half-life

Question 7

What are the many ways that radiation can be used?

Answer 7

Medical procedures including diagnosis and treatment of cancer
Sterilising food (irradiating food)
Sterilising medical equipment
Determining the age of ancient artefacts
Checking the thickness of materials
Smoke detectors (alarms)

Question 8

How is Alpha used in smoke detectors?

Answer 8

Alpha particles used in smoke detectors. The Alpha radiation will normally ionise the air within the detector creating a current.

The Alpha emitter is blocked when smoke enters the detector

The alarm is triggered by a microchip when the sensor no longer detects alpha

Question 9

How is Beta used in Measuring the thickness of materials?

Answer 9

As a material moves above a beta source, the particles that are able to penetrate it can be monitored using a detector
If the material gets thicker more particles will be absorbed, meaning that less will get through
If the material gets thinner the opposite happens
This allows the machine to make adjustments to keep the thickness of the material constant

Question 10

Why couldn’t an alpha source or a gamma source measure the thickness of materials?

Answer 10

Beta radiation is used because it will be partially absorbed by the material
If alpha particles were used all of them would be absorbed and none would get through
If gamma were used almost all of it would get through and the detector would not be able to sense any difference if the thickness were to change

Question 11

How are Gamma rays used in Diagnosis and treatment of cancer?

Answer 11

Radiotherapy is the name given to the treatment of cancer using radiation

Although radiation can cause cancer, it is also highly effective at treating it
Radiation can kill living cells. Some cells, such as bacteria and cancer cells, are more susceptible to radiation than others
Beams of gamma rays are directed at the cancerous tumour
Gamma rays are used because they are able to penetrate the body, reaching the tumour
The beams are moved around to minimise harm to healthy tissue whilst still being aimed at the tumour
A tracer is a radioactive isotope that can be used to track the movement of substances, like blood, around the body
A PET scan can detect the emissions from a tracer to diagnose cancer and determine the location of a tumour

Question 12

How is Gamma used in Sterilising food and medical equipment?

Answer 12

Gamma radiation is widely used to sterilise medical equipment
Gamma is most suited to this because:
It is the most penetrating out of all the types of radiation
It is penetrating enough to irradiate all sides of the instruments
Instruments can be sterilised without removing the packaging
Food can be irradiated in order to kill any microorganisms that are present on it
This makes the food last longer, and reduces the risk of food-borne infection

Question 13

What are the properties of the three sources of radiation?

Answer 13

Alpha is the most weakly penetrating and strongest ioniser
Beta and gamma have stronger penetrating power and weaker ionising power

Question 14

What is contamination?

Answer 14

The unwanted presence of materials containing radioactive atoms and other materials.

Question 15

What make a substance radioactive?

Answer 15

A substance is only radioactive if it contains radioactive atoms that emit radiation. Contamination occours when a radioactive isotope gets onto a material where it should not be often called a leak.

Question 16

What is Irradiation?

Answer 16

The process of exposing a material to alpha, beta or gamma radiation.

Question 17

What does irradiating a material do?

Answer 17

It does not make that material radioactive but it does kill all living cells.

Question 18

What is a use of Irradiation?

Answer 18

Irradiation can be used as a method of sterilisation. Surgical equipment is irradiated before being used in order to kill any micro-organisms on it before surgery

Food can be Irradiated to kill any micro- organisms within it making it last longer.

Question 19

What are the hazards of Irradiation and contamination?

Answer 19

Contamination can cause more harm than Irradiation due to the continuous exposure to radiation that it produces

Contamination is a particulary dangerous if a radioactive source gets into the human body. The internal organs will be irradiated as the source emits radiation as it moves through the body.

Question 20

What are the comparisons of irradiation and contamination?

Answer 20

Irradiation- Objects is exposed to radiation but does not become radioactive

Contamination- objects become radioactive and emits radiation.

Source of irradiation - Dangers is from radiation emitted outside the object

Source of contamination - Danger from radiation emitted within the object

Preventing Irradiation - Preventing by using shielding, such as lead and clothing.

Preventing Contamination - Prevented by safe handling of sources and airtight saftey clothing

Causes of Irradiation - caused by the presence of radioactive sources outside the body.

Causes of Contamination - Caused by inhalation or ingestion of radioactive sources

Question 21

What methods are used to protect against Irradiation and contamination?

Answer 21

It is important to reduce the risk of exposure to radiation
Radiation can mutate DNA in cells and cause cancer
Shielding is used to absorb radiation
Lead lined suits are used to reduce irradiation for people working with radioactive materials
The lead absorbs most of the radiation that would otherwise hit the person
To prevent contamination an airtight suit is used by people working in an area where there may have been a radiation leak
This prevents radioactive atoms from getting inside the person

Question 22

What does ionising radiation do to a human?

Answer 22

Ionising radiation can damage human cells and tissues if the atoms that make up the DNA strands are ionised then the DNA strand can be damaged.
If the DNA is damaged then the cell may die or be mutated. If a mutated cell replicates itself then a tumour may form.

Question 23

What does acute radiation do to humans?

Answer 23

It can cause skin burns, similar to severe sunburn
Radiation can reduce the amount of white blood cells in the body, making a person more susceptible to infections
Because of this, it is important to handle radioactive sources carefully

Question 24

Why is handling radiation carefully important?

Answer 24

To mitigate the risks of radiation exposure safe practices should be used
Radioactive sources should be kept in a shielded container when not in use, like a lead lined box.
Radioactive materials should only be handled when wearing gloves with tongs to increase distance
It may be appropriate to wear protective clothing to prevent the body becoming contaminated
The time that a radioactive source is being used for should be limited

Question 25

Why is it important to regulate exposure to Radiation?

Answer 25

There are harmful effects of radiation, It is important to regulate the exposure of humans to radiation.

The amount of radiation received by a person is called the dose and is measured in sieverts (Sv)
One sievert is a very big dose of radiation
It would cause acute radiation poisoning
People would normally receive about 3 mSv (0.003 Sv) in one year
To protect against over-exposure, the dose received by different activities is measured

Question 26

How are different people affected by exposure to radiation?

Answer 26

The amount of radiation that a person receives is affected by a person’s occupation, lifestyle or location
Some areas around the world have higher background radiation because they are closer to sources of radiation
People that work with nuclear radiation receive more radiation

Question 27

What is a safe way to Dispose of radioactive waste?

Answer 27

If an isotope has a long half life then a sampleof it will decay slowly. Although it may not emit a lot of radiation, it will remain radioactive for a very long time
Sources with long half-life values present a risk of contamination for a much longer time
Radioactive waste with a long half-life is buried underground to prevent it from being released into the environment