Radioactivity

What is the structure of an atom?

Atomic structure

• Atoms are the building blocks of all matter

• They are incredibly small, with a radius of only 1 × 10^-10 m

• Atoms have a tiny, dense nucleus at their centre, with electrons orbiting around the nucleus

• The radius of the nucleus is over 10,000 times smaller than the whole atom, but it contains almost all of the mass of the atom

Atomic structure of lithium

Diagram showing the structure of a Lithium atom. If drawn to scale then the electrons would be around 100 metres away from the nucleus!

Particles in the atom

• The nucleus contains:

  • Protons - positively charged particles with a relative atomic mass of one unit

  • Neutrons – no charge, and also with a relative atomic mass of one unit

• Almost all of the atom is empty space, but moving around the nucleus there are:

  • Electrons – negative charge with almost no mass (1/2000 the mass of a proton or neutron)

• The properties of each of the particles are shown in the table below:

Table of particle properties

Particle	Location	Relative charge	Relative mass
proton	in the nucleus	+1	1
neutron	in the nucleus	0	1
electron	orbiting the nucleus	−1	1/2000 (negligible)

 Charge in the atom

• Although atoms contain particles of different charge, the total charge within an atom is zero

  • This is because the number of electrons is equal to the number of protons

• The following table sets out the calculation of the total charge in the lithium atom in the diagram above:

Calculating total charge table

Particle	Relative charge	Number of particles in lithium atom	number × relative charge	Total charge
proton	+1	3	+3	(+3) + 0 + (−3) = 0
neutron	0	4	0
electron	−1	3	−3

 

• If an atom loses electrons, then it is said to be ionised

• Symbols are used to describe particular nuclear by their element symbol, atomic number and mass number

  • This notation is called nuclear notation

Carbon 12 in nuclear notation

What is atomic and mass number?

Atomic & mass number

Atomic number

• The number of protons in an atom is called its atomic number (it can also be called the proton number)

  • Elements in the periodic table are ordered by their atomic number

  • Therefore, the number of protons determines which element an atom is

• The atomic number of a particular element is always the same

• For example:

  • Hydrogen has an atomic number of 1. It always has just one proton

  • Sodium has an atomic number of 11. It has 11 protons

  • Uranium has an atomic number of 92. It has 92 protons

• The atomic number is also equal to the number of electrons in an atom

  • This is because atoms have the same number of electrons and protons in order to have no overall charge

Mass number

• The total number of particles in the nucleus of an atom is called its mass number 

• The mass number is the number of protons and neutrons in the atom

• The number of neutrons can be found by subtracting the atomic number from the mass number

number of neutrons = mass number – atomic number

• For example, if a sodium atom has a mass number of 23 and an atomic number of 11, then the number of neutrons would be 23 – 11 = 12

Nuclear notation

• The mass number and atomic number of an atom are shown by writing them with the atomic symbol

  • This is called nuclear notation

• Here are three examples:

Examples of nuclear notation for atoms of Hydrogen, Sodium and Uranium

• The top number is the mass number

  • This is equal to the total number of particles (protons and neutrons) in the nucleus

• The lower number is the atomic number

  • This is equal to the total number of protons in the nucleus

• The atomic and mass number of each type of atom in the examples above is shown in this table:

Number of protons, neutrons & electrons table

Atom	Number of protons (atomic number)	Number of neutrons (mass number − atomic number)	Number of electrons (same as atomic number)
hydrogen	1	1	1
sodium	11	12	11
uranium	92	143	92

What is an isotope?

Isotopes

• For a particular element, the number of protons is always the same, but the number of neutrons can be different

  • This is because the number of protons determines the element e.g. carbon atoms have 6 protons and iron atoms have 26 protons

• An isotope is defined as:

  An atom, or atoms, of the same element that have an equal number of protons but a different number of neutrons

• Each element can have more than one isotope

Isotopes of hydrogen

• Some isotopes are more unstable than others due to the imbalance of protons and neutrons, which means

  • They may be more likely to decay

  • They may be less likely to occur naturally

• For example, about 2 in every 10 000 atoms of hydrogen are the isotope deuterium

  • The isotope tritium is even rarer (about 1 in every billion billion atoms of hydrogen)

Why are particles radioactive and what are the different types of radiation?

Types of radiation

• Some atomic nuclei are unstable and radioactive

• This is because of an imbalance of protons or neutrons in the nucleus

• Carbon-14 is an example of an isotope of carbon which is unstable

• This is because it has two extra neutrons compared to a stable nucleus of carbon-12

Stable and unstable isotopes of carbon

Carbon-12 is stable, whereas carbon-14 is unstable because it has two extra neutrons

• Unstable nuclei can emit radiation to become more stable

• Radiation can be in the form of a high-energy particle or wave

• This process is known as radioactive decay

• As the radiation moves away from the nucleus, it takes some energy with it

• This makes the nucleus more stable

Radioactive decay of a nucleus

Unstable nuclei decay by emitting high energy particles or waves

• When an unstable nucleus decays, it emits radiation

• The different types of radiation that can be emitted are:

  • Alpha (α) particles

  • Beta (β^-) particles

  • Gamma (γ) radiation

• These changes are spontaneous and random

What are the properties of the different types of radiation?

Properties of alpha, beta and gamma radiation

Alpha particles

• The symbol for alpha is α

• An alpha particle is the same as a helium nucleus

• This is because it consists of two neutrons and two protons

Beta particles

• The symbol for beta is β⁻

• Beta particles are high-energy electrons

• They are produced in nuclei when a neutron changes into a proton and an electron

Gamma rays

• The symbol for gamma is γ

• Gamma rays are electromagnetic waves

• They have the highest energy of the different types of electromagnetic waves

Alpha, beta & gamma radiation

Alpha particles, beta particles and gamma waves can be emitted from unstable nuclei

Properties of alpha, beta & gamma

• Alpha (α), beta (β) and gamma (γ) radiation can be identified by their:

  • Nature (what type of particle or radiation they are)

  • Ionising ability (how easily they ionise other atoms)

  • Penetrating power (how far can they travel before they are stopped completely)

• Alpha, beta and gamma penetrate materials in different ways

• This means they are stopped, or reduced, by different materials

Penetrating power of alpha, beta and gamma

Alpha, beta and gamma are different in how they penetrate materials. Alpha is the least penetrating, and gamma is the most penetrating

• Alpha is stopped by paper, whereas beta and gamma pass through it

• Beta is stopped by a few millimetres of aluminium

• Gamma rays can pass through aluminium but are only partially stopped by thick lead

Summary of the properties of nuclear radiation

Particle	Nature	Range in air	Penetrating power	Ionising ability
Alpha (α)	helium nucleus (2 protons, 2 neutrons)	a few cm	low; stopped by a thin sheet of paper	high
Beta (β)	high-energy electron	a few 10s of cm	moderate; stopped by a few mm of aluminium foil or Perspex	moderate
Gamma (γ)	electromagnetic wave	infinite	high; reduced by a few cm of lead	low

How do you investigate the penetration powers of different types of radiation using either radioactive sources or simulations?

Aim of the experiment

•  The aim of this experiment is to investigate the penetration powers of different types of radiation using either radioactive sources or simulations

Variables:

• Independent variable = Absorber material

• Dependent variable = Count rate

• Control variables:

  • Radioactive source

  • Distance of GM tube to source

  • Location / background radiation

Equipment List

Equipment	Purpose
radioactive sources (α, β and γ)	to use as a source of radioactive emission
ruler	to measure the distance between the source and detector
mount for radioactive source	to secure the source in place
Geiger-Muller tube and counter	to measure the count rate of a radioactive source
tongs	to safely handle the sources at a distance
selection of absorbing materials (paper, aluminium foil, lead)	to place between the source and detector to investigate effect on count rate
lead-lined containers for radioactive sources	to store sources in when not in use

 

• Resolution of measuring equipment:

  • Ruler = 1 mm

  • Geiger-Müller tube = 0.01 μS/hr

Method

Apparatus for investigating the penetrating powers of different types of radiation

1. Connect the Geiger-Müller tube to the counter and, without any sources present, measure background radiation over a period of one minute

2. Repeat this three times, and take an average. Subtract this value from all subsequent readings.

3. Place a radioactive source a fixed distance of 3 cm away from the tube and take another reading of count rate over a period of one minute

4. Take a set of absorbers, i.e. some paper, several different thicknesses of aluminium (increasing in 0.5 mm intervals) and different thicknesses of lead

5. One at a time, place these absorbers between the source and the tube and take another reading of count rate over a period of one minute

6. Repeat the above experiment for other radioactive sources

Analysis of results

• If the count rate is similar to background levels (allowing for a little random variation), then the radiation has all been absorbed

  • Note: some sources will emit more than one type of radiation

• If the count rate reduces when paper is present, the source is emitting alpha

• If the count rate reduces when a few mm of aluminium is present, then the source is emitting beta

• If some radiation is still able to penetrate a few mm of lead, then the source is emitting gamma

 Penetrating power of alpha, beta and gamma radiation

Evaluating the experiment

Systematic Errors:

• Make sure that the sources are stored well away from the counter during the experiment

• Conduct all runs of the experiment in the same location to avoid changes in background radiation levels

Random Errors:

• The accuracy of such an experiment is improved with using reliable sources with a long half-life and an activity well above the natural background level

Safety considerations

• When not using a source, keep it in a lead-lined container

• When in use, try and keep a good distance (a metre or so) between yourself and the source

• When handling the source, do so using tweezers (or tongs) and point the source away from you

Alpha, beta, gamma & neutron emission

Alpha decay

• During alpha decay, an alpha particle is emitted from an unstable nucleus

• A completely new element is formed in the process

Alpha decay usually happens in large unstable nuclei, causing the overall mass and charge of the nucleus to decrease

• An alpha particle is a helium nucleus

  • It is made of 2 protons and 2 neutrons

• When the alpha particle is emitted from the unstable nucleus, the mass number and atomic number of the nucleus changes

  • The mass number decreases by 4

  • The atomic number decreases by 2

• Alpha decay can be represented by the following nuclear equation:

Beta decay

• During beta decay, a neutron changes into a proton and an electron

  • The electron is emitted and the proton remains in the nuclei

• A completely new element is formed because the atomic number changes

Beta decay often happens in unstable nuclei that have too many neutrons. The mass number stays the same, but the atomic number increases by one

• A beta particle is a high-speed electron

• It has a mass number of 0

  • This is because the electron has a negligible mass, compared to neutrons and protons

• Therefore, the mass number of the decaying nuclei remains the same

• Electrons have an atomic number of -1

  • This means that the atomic number of the new nucleus will increase by 1 to balance the overall atomic number before and after the decay

• Beta decay can be represented by the following nuclear equation:

Gamma decay

• During gamma decay, a gamma ray is emitted from an unstable nucleus

• This process makes the nucleus less energetic but does not change its structure

  

Gamma decay does not affect the mass number or the atomic number of the radioactive nucleus, but it does reduce the energy of the nucleus

• The gamma ray that is emitted has a lot of energy, but no mass or charge

• Gamma decay can be represented by the following nuclear equation:

  

• Notice that the mass number and atomic number of the unstable nucleus remains the same during the decay

Neutron emission

• A small number of isotopes can decay by emitting neutrons

• When a nucleus emits a neutron:

  • The atomic number (number of protons) does not change

  • The mass number (total number of nucleons) decreases by 1

• Neutron emission can be represented by the following nuclear equation:

  

• Notice that the atomic number remains the same during the decay but the mass number has changed

  • This means an isotope of the original element has formed

How an one detect ionising radiation?

Detecting radiation

• Ionising radiation can be detected using

  • photographic film

  • a Geiger–Müller tube

Photographic film

• Photographic films detect radiation by becoming darker when it absorbs radiation, similar to when it absorbs visible light

  • The more radiation the film absorbs, the darker it is when it is developed

• People who work with radiation, such as radiographers, wear film badges which are checked regularly to monitor the levels of radiation absorbed

• To get an accurate measure of the dose received, the badge contains different materials that the radiation must penetrate to reach the film

  • These materials may include aluminium, copper, paper, lead and plastic

• The diagram shows what a typical radiation badge looks like:

A badge containing photographic film can be used to monitor a person’s exposure to radiation

Geiger-Müller tube

• The Geiger-Müller tube is the most common device used to measure and detect radiation

• Each time it absorbs radiation, it transmits an electrical pulse to a counting machine

• This makes a clicking sound or displays the count rate

• The greater the frequency of clicks, or the higher the count rate, the more radiation the Geiger-Müller tube is absorbing

  • Therefore, it matters how close the tube is to the radiation source

  • The further away from the source, the lower the count rate detected

A Geiger-Müller tube (or Geiger counter) is a common type of radiation detector

What is background radiation and what are the sources of it?

Background radiation

• It is important to remember that radiation is a natural phenomenon

• Radioactive elements have always existed on Earth and in outer space

• However, human activity has added to the amount of radiation that humans are exposed to on Earth

• Background radiation is defined as:

  The radiation that exists around us all the time

• Every second of the day there is some radiation emanating from natural sources such as:

  • Rocks

  • Cosmic rays from space

  • Foods

Chart of Background Radiation Sources

Background radiation is the radiation that is present all around in the environment. Radon gas is given off from some types of rock

• There are two types of background radiation:

  • Natural sources

  • Artificial (man-made) sources

Natural Sources of Background Radiation

Radon gas from rocks and buildings

• Airborne radon gas comes from rocks in the ground, as well as building materials e.g. stone and brick

• This is due to the presence of radioactive elements, such as uranium, which occur naturally in small amounts in all rocks and soils

  • Uranium decays into radon gas, which is an alpha emitter

  • This is particularly dangerous if inhaled into the lungs in large quantities

• Radon gas is tasteless, colourless and odourless so it can only be detected using a Geiger counter

• Levels of radon gas are generally very low and are not a health concern, but they can vary significantly from place to place

Cosmic rays from space

• The sun emits an enormous number of protons every second

• Some of these enter the Earth’s atmosphere at high speeds

• When they collide with molecules in the air, this leads to the production of gamma radiation

• Other sources of cosmic rays are supernovae and other high energy cosmic events

Carbon-14 in biological material

• All organic matter contains a tiny amount of carbon-14

• Living plants and animals constantly replace the supply of carbon in their systems hence the amount of carbon-14 in the system stays almost constant

Radioactive material in food and drink

• Naturally occurring radioactive elements can get into food and water since they are in contact with rocks and soil containing these elements

• Some foods contain higher amounts such as potassium-40 in bananas

• However, the amount of radioactive material is minuscule and is not a cause for concern

Artificial Sources of Background Radiation

Nuclear medicine

• In medical settings, nuclear radiation is utilised all the time

• For example, X-rays, CT scans, radioactive tracers, and radiation therapy all use radiation

Nuclear waste

• While nuclear waste itself does not contribute much to background radiation, it can be dangerous for the people handling it

Nuclear fallout from nuclear weapons

• Fallout is the residue radioactive material that is thrown into the air after a nuclear explosion, such as the bomb that exploded at Hiroshima

• While the amount of fallout in the environment is presently very low, it would increase significantly in areas where nuclear weapons are tested

Nuclear accidents

• Nuclear accidents, such as the incident at Chornobyl, contribute a large dose of radiation to the environment

• While these accidents are now extremely rare, they can be catastrophic and render areas devastated for centuries

Accounting for background radiation

• Background radiation must be accounted for when taking readings in a laboratory

• This can be done by taking readings with no radioactive source present and then subtracting this from readings with the source present

• This is known as the corrected count rate

Measuring background count rate

The background count rate can be measured using a Geiger-Müller (GM) tube with no source present

• For example, if a Geiger counter records 24 counts in 1 minute when no source is present, the background radiation count rate would be:

  • 24 counts per minute (cpm)

  • 24/60 = 0.4 counts per second (cps)

Measuring the corrected count rate of a source

The corrected count rate can be determined by measuring the count rate of a source and subtracting the background count rate

• Then, if the Geiger counter records, for example, 285 counts in 1 minute when a source is present, the corrected count rate would be:

  • 285 − 24 = 261 counts per minute (cpm)

  • 261/60 = 4.35 counts per second (cps)

• When measuring count rates, the accuracy of results can be improved by:

  • Repeating readings and taking averages

  • Taking readings over a long period of time

How does the activity of a radioactive source change over a period of time, and how can it be measured?

Activity & decay

• Objects containing radioactive nuclei are called sources of radiation

• Sources of radiation decay at different rates which are defined by their activity

• The activity of a radioactive source is defined as:

  The rate at which the unstable nuclei decay

• Activity is measured in becquerels

  • The symbol for Becquerels is Bq

• 1 Becquerel is equal to 1 nucleus in the source decaying in 1 second

How does activity vary with time?

• The activity of a radioactive source decreases with time

  • This is because each decay event reduces the overall number of radioactive particles in the source

• Radioactive decay is a random process

• The randomness of radioactive decay can be observed by measuring the count rate of a source using a Geiger-Muller (GM) tube

• When the count rate is plotted against time, fluctuations can be seen 

• These fluctuations provide evidence for the randomness of radioactive decay

The decreasing activity of a source can be shown on a graph against time. The fluctuations show the randomness of radioactive decay

What is a half-life?

Half life

• It is impossible to know when a particular unstable nucleus will decay

• It is possible to find out the rate at which the activity of a sample decreases

  • This is known as the half-life

• Half-life is defined as:

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

• In other words, the time it takes for the activity of a sample to fall to half its original level

• Different isotopes have different half-lives and half-lives can vary from a fraction of a second to billions of years in length

Measuring half life

• To determine the half-life of a sample, the procedure is:

  • 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

Half life calculationsHalf-life

• Scientists can measure the half-lives of different isotopes accurately

• Uranium-235 has a half-life of 704 million years

  • This means it would take 704 million years for the activity of a uranium-235 sample to decrease to half its original amount

• Carbon-14 has a half-life of 5700 years

  • So after 5700 years, there would be 50% of the original amount of carbon-14 remaining

  • After two half-lives or 11 400 years, there would be just 25% of the carbon-14 remaining

• With each half-life, the amount remaining decreases by half

A graph can be used to make half-life calculations

The graph shows how the activity of a radioactive sample changes over time. Each time the original activity halves, another half-life has passed

• The time it takes for the activity of the sample to decrease from 100% to 50% is the half-life

• It is the same length of time as it would take to decrease from 50% activity to 25% activity

• The half-life is constant for a particular isotope

• The following table shows that as the number of half-life increases, the proportion of the isotope remaining halves

Half life calculation tableHalf-life

number of half lives	proportion of isotope remaining
0	100%
1	50%
2	25%
3	12.5%
4	6.25%

What are the uses of radioactivity?

Uses of radioactivity

• Radioactivity has many uses, such as:

  • Smoke detectors (alarms)

  • Monitoring the thickness of materials

  • Medical procedures including diagnosis and treatment of cancer

  • Sterilising food (irradiating food)

  • Sterilising medical equipment

  • Determining the age of ancient artefacts

• The properties of the different types of radiation determine which one is used in a particular application

Smoke detectors

• Alpha particles are 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

When no smoke is present, alpha particles ionise the air and cause a current to flow. When smoke is present, alpha particles are absorbed and current is prevented from flowing which triggers the alarm

Measuring the thickness of materials

• When a material, such as aluminium foil, moves above a beta source, some beta particles will be absorbed, but most will penetrate

  • The amount of beta particles passing through the material can be monitored using a detector

• If the material gets thicker, more particles will be absorbed, and the count rate will decrease

• If the material gets thinner, fewer particles will be absorbed, and the count rate will increase

• This allows the manufacturer to make adjustments to keep the thickness of the material constant

Beta particles can be used to measure the thickness of thin materials such as paper, cardboard or aluminium foil

• Beta radiation is used because the material will only partially absorb it

  • If an alpha source were used, all alpha particles would be absorbed regardless of material thickness

  • If a gamma source were used, almost all gamma rays would be detected regardless of material thickness

Diagnosis and treatment of cancer

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

  • Note: this is different to chemotherapy which is a drug treatment for cancer

• Although radiation can cause cancer, it is also highly effective at treating it

• Ionising 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 as they can penetrate the body and reach 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

Radiation therapy is a type of cancer treatment which targets the tumour with ionising radiation

Sterilising food and medical equipment

• 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 infections

Food that has been irradiated carries this symbol, called the Radura. Different countries allow different foods to be irradiated

What is the difference between contamination and irradiation?

Contamination & irradiation

Contamination

• Contamination is defined as:

  The accidental transfer of a radioactive substance onto or into a material

• A substance is only radioactive if it contains a source of ionising radiation

• Contamination occurs when a radioactive isotope gets onto a material where it should not be

  • It is almost always a mistake or an accident e.g. a radiation leak

• As a result of this, the small amounts of the isotope in the contaminated areas will emit radiation and the material becomes radioactive

Irradiation

• Irradiation is defined as:

  The process of exposing a material to ionising radiation

• Irradiating a substance does not make it radioactive

  • However, it can kill living cells

• Irradiation is usually a deliberate process, such as in the sterilisation of food or medical equipment

  • 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 to make it last longer

This sign is the international symbol indicating the presence of a radioactive material

Protection from irradiation and contamination

• Radiation can mutate DNA in cells and cause cancer through both irradiation and contamination

  • Therefore, it is important to reduce the risk of exposure to radiation

• Contamination is particularly dangerous if a radioactive source gets inside the human body

  • For example, through the inhalation of radioactive gas particles, or ingesting contaminated food

  • The internal organs will be irradiated as the source emits radiation as it moves through the body

• To prevent irradiation, shielding can be 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 worn by people working in an area where a radioactive source may be present

  • This prevents radioactive atoms from getting on or into the person

Lead shielding is used when a person is getting an x-ray, as well as for people who work with radiation. Contamination carries much greater risks than irradiation

Differences between irradiation and contamination

• The differences between irradiation and contamination are summarised in the table below:

Comparison of irradiation and contamination table

	Irradiation	Contamination
description	when an object is exposed to a source of radiation but does not become radioactive	when an object becomes radioactive due to the presence of a source of radiation
source	exposure to source of radiation outside the object	exposure to source on or within the object
prevention	blocked by using shielding such as lead	radiation cannot be blocked once an object is contaminated, but can be prevented by handling the source safely
causes	caused by the deliberate exposure to radiation	caused by the accidental transfer of radioactive material

What are the dangers of radiation?

Dangers of ionising radiation

• All types of ionising radiation pose a danger if mishandled as they can

  • damage living cells and tissues

  • cause mutations which can lead to cancer

Effect of radiation on a living cell

Ionising radiation can cause damage to DNA. Sometimes the cell can successfully repair the DNA, but incorrect repairs can cause a mutation

• Highly ionising types of radiation are more dangerous inside the body (if a radioactive source is somehow ingested)

  • Alpha sources are the most ionising, so they are likely to cause the most harm to living cells inside the body

  • Gamma sources are the least ionising (about 20 times lower than alpha particles), so they are likely to cause the least harm to living cells inside the body

• Highly penetrating types of radiation are more dangerous outside the body

  • Gamma sources are the most penetrating, so they are able to pass through the skin and reach living cells in the body

  • Alpha sources are least penetrating, so they would be absorbed by the air before even reaching the skin

Safe handling of radioactive sources

• The risks of radiation exposure can be minimised by

  • handing sources of radiation safely

  • monitoring exposure to radiation

• To minimise the risks of contamination, safety practices must be followed, such as:

  • keeping radioactive sources in a shielded container when not in use, for example, a lead-lined box

  • wearing gloves and using tongs to handle radioactive materials

  • wearing protective clothing (particularly if the risk of inhalation or ingestion is high)

  • limiting the time that a radioactive source is outside of its container

• To minimise the risks of irradiation to workers, it is important to monitor their exposure to radiation 

  • To protect against over-exposure, the dose received by different activities is measured

  • A dosemeter measures the amount of radiation in particular areas and is often worn by radiographers, or anyone working with radiation

Badge for monitoring radiation exposure

A dosemeter, or radiation badge, can be worn by a person working with radiation in order to keep track of the amount of radiation they are receiving

Disposal of nuclear waste

• Nuclear waste must be treated appropriately, depending on the type of radiation it emits

  • Alpha-emitting nuclear waste is easily stored in plastic or metal canisters

  • Beta-emitting nuclear waste is stored inside metal canisters and concrete silos

  • Gamma-emitting nuclear waste requires storage inside lead-lined, thick concrete silos

• Radioactive waste of all types tends to emit dangerous levels of radiation for many years, so it must be stored securely for a very long time

• Typically, waste with the highest levels of radioactivity must be buried underground in secure, geologically stable locations

Dealing with radioactive waste

Depending on the type of radiation emitted, nuclear waste is treated in different ways

• Sources with long half-lives present a risk of contamination for a much longer time

• Radioactive waste with a long half-life can be buried underground to prevent radioactive from being released into the environment

• Radioactive waste must be stored in strong containers

  • The containers must be able to withstand harsh conditions over long periods

• Containers must be designed to resist rust and corrosion

  • Rust-proof containers are often expensive and challenging to manufacture

• The disposal site must have high security to prevent unauthorised access

• The location of the disposal site must have a low risk of natural disasters, e.g. earthquakes

• Carefully selecting the site and using strong containers will help prevent radioactive waste from leaking into groundwater

• Radioactive waste can also be diluted in large volumes of seawater

  • This helps to minimise the concentration of radioactive materials