S2/3 BGE Physics Course 1

Unit 1 - Waves and Radiation

5. Nuclear Radiation

Summary Notes

Topic 5 – Nuclear Radiation

Atomic Structure

Everything we see around us is made up of atoms.

Inside all of these atoms there is a nucleus.

The basic structure of an atom is shown in the diagram

below:

As indicated in the key, there are three different types of

particles: protons, neutrons and electrons. Protons

and Neutrons are referred to as nucleons as they are

found inside the nucleus of an atom. Electrons are

found in orbits around the outside of the nucleus.

Almost all of the mass of an atom is contained in the

nucleus and therefore the atom is described as being

almost entirely empty space.

Orbit

Orbit

Orbit

The overall size of the atom

can be compared to the size of

the Etihad Stadium in

Manchester. The size of the

nucleus can be compared to

the centre spot at kick-off.

Ionising Radiation

The three types of ionising radiation are alpha (α),

beta (β) and gamma (γ).

Type of Particle

What is it? Charge

Alpha Helium Nucleus +2

Beta Fast moving electron

-1

Gamma High frequency/ energy EM wave

0

Absorbing Ionising Radiation

Alpha particles (α) are the least penetrating of the

ionising radiations. It is absorbed by a piece of paper or

a few centimetres (cm) of air.

Beta particles (β) can pass through paper and air but

are absorbed by millimetres (mm) of Aluminium.

Gamma rays (γ) can pass through air, paper and

aluminium. They will be absorbed by centimetres (cm) of

Lead, however this is not entirely 100%.

Not 100% absorbing

Background Radiation

This is the natural radiation that is all around us.

It comes from many different sources as shown below.

Source Percentage (%)

Radon Gas 50.0

Ground and Buildings 14.0

Medical 14.0

Food and Drink 11.5

Cosmic Rays 10.0

Nuclear power and weapons 0.3

Other 0.2

Natural Radiation Sources

Radon gas comes from rocks and soil

Gamma rays from the ground

Carbon and potassium from the body

Cosmic rays from the Sun

Artificial Radiation Sources

Medical applications such as X-Rays and

radioisotopes used in scans and cancer treatments

Fallout from nuclear weapons

Fallout from previous nuclear explosions (e.g.

Chernobyl and Fukushima)

Nuclear waste from power stations

Monitoring Nuclear Radiation

Nuclear radiation must be closely monitored as it can

kill or damage living tissue.

After the nuclear accident at Chernobyl (Ukraine)

Reactor no.4 on April 24th 1986, many nuclear workers

and services personnel died soon after the accident.

However there were many more people who died in the

years afterwards, with their lives being cut short by

different forms of cancer. There were also babies born

over the next few years with many different defects at

birth, which was also caused by the radiation originating

from the explosion.

Operators in the control

centre before the accident

at Chernobyl.

Reactor no.4 at Chernobyl

after the accident.

Detecting Nuclear Radiation

Nuclear Radiation can be detected by:

Film Badges

Geiger Counters (Geiger-Muller Tubes)

Scintillation Counters

Film Badges

Hospital staff and people who work in nuclear power

plants are exposed to more radiation than the average

person. Therefore it is very important to keep a record of

how much radiation they are being exposed to.

Any occupations in hospitals that are involved with

radiation are required by law to wear a film badge. An

example of a typical film badge can be seen in the

diagram below.

Each film badge consists of a sheet of photographic

film which will change colour or “fog” / “go cloudy”

when radiation falls on it. They consist of different filters,

each one designed to only allow certain radiations to

pass through. They will indicate:

The type of radiation that a worker is exposed to.

The quantity of radiation that the worker has been

exposed to.

Geiger Counters (GM Tube)

Geiger counters are seen in videos and films where they

emit sound in the form of a continual click.

When the reading on the display increases the

frequency of the clicking sound increases, and therefore

the radiation or activity being measured increases.

Scintillation Counters

Radiation can be converted into tiny bursts of light called

scintillations, which can be observed by the naked eye.

These are counted using a light detector and an

electronic circuit.

Nuclear Radiation used in Medicine

1) Diagnosis

Nuclear Radiation can be used as a tracer into the body

in the form of a drink or an injection.

Gamma radiation is used as it is the most penetrating of

the three types of ionising radiation. (Alpha and beta

radiation would not be detectable outside of the body)

The radiation will lose its strength quickly and it will not

be detrimental to the patient.

The radioactive material is taken out of the bloodstream

by the kidneys. After approximately 10 minutes all of the

radiation should be in the bladder. The gamma camera

takes continual readings over the next 20 minutes to

check on the kidney function to make sure that each

kidney is functioning properly.

(In Industry we looked in the Electromagnetic Spectrum

Topic 1.4 on how gamma radiation can be used to check

the location of leaks in underground water pipes and

non-destructive testing on metals to find flaws.)

2) Treatment

Chemotherapy (chemo) is a process where different

types of drugs are used to treat the cancer.

The goal of chemotherapy is to stop cancer spreading to

other parts of the body. (Non-radioactive)

Radiotherapy is the use of high energy radiation waves

to destroy or damage cancer cells. High doses of

radiation (Gamma Rays and hard X-Rays) are sent

directly to the cancer cells or tumour. The radiation can

also affect healthy cells but they can repair themselves,

however cancer cells cannot.

Chemotherapy and Radiotherapy can be combined

together for a patient’s treatment. The Chemotherapy

usually comes first before radiotherapy to stop the

cancer spread, before directing the high doses of

radiation directly to the cancerous cells or tumours.

Chemotherapy and Radiotherapy can be administered

at the same time, if the cancer is located in areas of the

body that is difficult to treat and has a high likelihood of

spreading.

Chemotherapy Radiotherapy

Nuclear Radiation as an Energy Source

In the UK there are currently 15 nuclear reactors with a

total generating capacity of 10GW of electrical power.

This accounts for 20% of the UK’s electrical energy

production.

The Nuclear Reactor

In a nuclear power station the nuclear reactor is used to:

Generate heat energy that will turn water into steam

This high pressure steam spins the turbines around

The turbines are linked to the electrical generators

(alternators) which produce electrical energy

Nuclear Radiation used in Energy Production

Advantages

A small quantity of nuclear fuel would produce the

equivalent energy as a huge quantity of fossil fuel.

It does not produce any greenhouse gases such as

carbon dioxide, which would harm the environment

with the possible effects of global warming.

Does not use fossil fuels which are running out.

Disadvantages

Nuclear fuel will eventually run out as it is a non-

renewable energy source.

Nuclear waste is difficult to store safely and to

dispose of.

Nuclear waste is still highly radioactive for

thousands of years.

Nuclear accidents such as Chernobyl and

Fukushima are very serious and have major affects

over a wide area for many years.

Radioactive Hazard Sign

The radioactive hazard symbol can be seen on the door

of the room that it is contained in within a school.

The sign is also attached to the door handle of a

classroom where a class experiment is taking place

using radioactive sources.

Handling Radioactive Sources Safety Procedures

Always use forceps or a lifting tool or wear special gloves to remove a source – never use bare hands.

Direct the source towards a wall or a window, so that it will point away from the body.

Never point the source at your eyes.

Wash your hands immediately after performing any experiment that involves radioactive sources. (proper 20 seconds wash with soap or hand gel)

Reducing your Exposure to Radiation

There are three ways in which exposure to radiation can be reduced

Shielding – shield the source of radiation with an appropriate thickness of absorber. (usually lead as most sources emit alpha, beta and gamma).

Limiting the time – radioactive sources should be moved and used as quickly as possible to reduce the radiation present. This time and location should be recorded in the log book.

Distance from source – the further you are from the source the less radiation you will receive.