Download - 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.