Beyond the EU: DORA and NIS 2 Directive's Global Impact
26 radioactivity-part-a
1. Animated Science
2021
26 Radioactivity
3.8.1.1-5
Part A
26.1 Discovery of the Nucleus
26.2 Alpha Beta Gamma
26.3 More on ABG Inverse Sq
26.4 Dangers of Rad
Part B
26.5 Radioactive Decay
26.6 Radioactive Decay Theory
26.7 Isotopes in Use
26.8 More in Decay Modes
26.9 Nuclear Radius
2. Animated Science
2021
Take care not to mix units when
calculating. For instance, you
may encounter activities given in
Becquerel's and count rates
stated in counts per minute; half
lives are often quoted in
reference works using the most
relevant time unit, be it seconds
or years.
6. Animated
Science
2021
Mr D Powell
2021
Animated Science
2021
26.1 Discovery of the Nucleus – how did
we work it all out?
INSPIRE
C
How big is the nucleus – factual
recall?
I know how the nucleus was discovered &
I can use a ZN graph for a decay
I can describe in detail the experiments used to
understand the nucleus?
Estimate radius from closest approach of
alpha particle and link to E-fields
A
B
Rutherford alpha particle scattering experiment
scattered alpha
particles
microscope to view
zinc sulphide screen,
and count alpha
particles
vary angle of
scattering
observed
radium
source of
alpha
particles
thin gold
foil
alpha particle
beam
zinc sulphide
screen, tiny dots of
light where struck
by alpha particle
lead block to
select narrow
beam of alpha
particles
http://hyperphysics.phy-
astr.gsu.edu/hbase/rutsca.
html
15. Animated Science
2021
Probing the Nucleus – Rutherford Scattering
Rutherford alpha particle scattering experiment
scattered alpha
particles
microscope to view
zinc sulphide screen,
and count alpha
particles
vary angle of
scattering
observed
radium
source of
alpha
particles
thin gold
foil
alpha particle
beam
zinc sulphide
screen, tiny dots of
light where struck
by alpha particle
lead block to
select narrow
beam of alpha
particles
nucleus
1
2
3
4
5
1
2
3
4
5
135
90
50
30
20
By firing alpha particles at a heavy
gold nucleus Rutherford could easily
see that atoms were mostly space
with a large positive nucleus in the
centre.
16. Animated Science
2021
Plenary / Review Task…
On a whiteboard on your own without looking at your notes,
use the image and your ideas to take us from 400BC to 1932
and the model day understanding of this image….then show it
in a pair!
Easy way write 1-5 on your board…
Harder… stop at 1800,1897,1909,1911 on the way…
1
2
3
4
5
17. Animated Science
2021
Christmas Lecture Video Review…. 8mins
• Watch the video on your own.
• Take at least a ½ page in your book
• Make notes as you go.
• Try and use these key headings for some
rough notes
• Add as much detail as you wish.
• We will review after
Rutherford
Scattering
Forces
Conclusions
Particles
Motion
Equipment
18. Animated Science
2021
Fuzzy boundaries?
Christmas Lecture Video Review…. 8mins
• Evacuated glass tube ( to allow easy passage of alphas particles)
• Radioactive source of alpha beamed onto a gold foil.
• Detectors (GM tubes) pick up if they go through or are deflected.
• A count is kept of where they go to so 536,000 go forwards
• Reflection is very rare only 4!
• If atom was a diffuse ball of charge nothing would bounce back
• They realised when it bounced back the positive charge was shown to be
concentrated in the centre of an atom. This is called scattering!
• He worked out the energy they started with (0.5mv2 balanced with the repulsion
by the nucleus (positive repels positive)
• Size he found that the diameter of the nucleus was around 2x 10-15m or 2 fm
• 1fm = 1x 10-15m
• Hence the typical atom is 0.1nm or 100,000 fm
• ratio is 10,000:1 so the atom is mostly space!
Atom Nucleus diameter fm Atomic diameter fm Ratio
Hydrogen 2 50,000 25000:1
Uranium 15 230,000 15300:1
Typical 10 100,000 10,000:1
19. Animated Science
2021
Instead of bits of atom, Rutherford found that a small proportion of the alpha
particles were deflected, while an even smaller proportion bounced right back.
From analysis of these observations he concluded:
Most of the atom was empty space.
The positive charge was concentrated in a very small space
The diameter of the nucleus was in the order of 1:10,000 smaller than the
atom
The alpha particles that were deflected back had to be travelling in a line with
the nucleus.
Rutherford’s estimates were not far out. Later research has shown the nuclear
radius to be in the order of 1.5 × 10-14 m. However the boundary is not sharp, but
rather fuzzy, as the nucleus is a very dynamic entity due to protons, neutron and
atomic force differences.
Rutherford Scattering Conclusions…
Atomic Nucleus
20. Animated Science
2021
26.1 Distance of closest Approach…
1) Explain the basic idea of what happens &
the importance of the experiment?
3) Explain how the formula for electrostatic
force applies, write it down and define for the
problem…
2) Explain how the formula for electric
potential energy applies, write it down and
define for the problem…
5) Combine the two formula and rearrange to something useful.
(harder)
6) Write out example(s) of a calculation to work out the distance….
4) Diagram (Low challenge-> Medium if explained)
22. Animated Science
2021
Scattering Formulae (harder)
Rutherford’s picture of alpha scattering
Assumptions:
alpha particle is the He nucleus, charge +2e
gold nucleus has charge + Ze, and is much more
massive than alpha particles
scattering force is inverse square electrical
repulsion
scattering angle
‘aiming error’ b
gold nucleus
charge + Ze
alpha particle
scattered
equal force F but
nucleus is massive,
so little recoil
charge +2e
For calculations
d
force F =
2Ze2
40d2
There are complex formulae that we can use to work out the distance of
closest approach. You will not have to learn these but should appreciate
some of the maths involved. At the very least the idea of the forces
involved
http://phet.colorado.edu/en/simulation/rutherford-scattering
24. Animated Science
2021
Distance of Closest Approach
NB: Ep = qV
Ep/q = V
&
V = Q/4or
Hence…
Ep = Qq/4or
For this situation
the potential
energy
U = Ep
26. Animated Science
2021
Summary Question...
For an alpha particle with an initial KE of 6MeV fired at a gold nucleus find the
distance of closest approach of the alpha and the nucleus...
28. Animated
Science
2021
Mr D Powell
2021
Animated Science
2021
26.2 Properties of , ,
INSPIRE
C
I know about , , and their
main properties/dangers
I can plan or explain how I can conduct experiments to look
at radioactive particles & explain how a GM tube works
(dead time?)
I can deduce particle interactions from a cloud chamber / GM tube
and can explain the difficulties with them.
Conduct a practical to look at absorption in metal of
(page 173)
A
B
29. Animated Science
2018
Radioactive Decay Main Quick Summary GCSE
1) Alpha () – an atom decays into a new
atom and emits an alpha particle (2
protons and 2 neutrons – the nucleus of a
helium atom)
2) Beta () – an atom decays into a new
atom by changing a neutron into a proton
and electron. (n p + e-) The fast
moving, high energy electron is called a
beta particle.
3) Gamma () – after or decay surplus
energy is sometimes emitted. This is
called gamma radiation and has a very
high frequency with short wavelength.
The atom is not changed. Comes from the
nucleus
Unstable
nucleus
Unstable
nucleus
New nucleus
New
nucleus
Alpha particle
Beta particle
Gamma
radiation
Key: = n = p = e-
Unstable
nucleus
New
nucleus
or
31. Animated Science
2020
Beta Decay/ part recap....
In this case a
neutron converts to
a proton, -, anti-
In this case a
proton converts to
a neutron, +,
33. Animated Science
2018
Cloud Chamber
https://youtu.be/NIsVYozRDPw
This cloud chamber video shows how
background radiation is passing through our
bodies and the atmosphere all the time.
The chamber works by making a vapour of
ethanol in the chamber and the radiation
causes the vapour to coalesce together to form
mini droplets. In some ways it is like mist
forming on a cold day.
The second video is where we have used an
Alpha emitter to show the particles…
https://youtu.be/LS3SwB8w9-Y
Alpha Source
Background Alpha
34. Animated Science
2021
This is an alpha particle
breaking from the Pb210
nucleus. As it is 2p & 2n and is
charged +2 it is heavy and
causes a large ion trail.
n n
p
p
39. Animated Science
2021
Track shows a possible muon
decay into two hidden neutrinos,
and an electron. Can also happen
with + you can tell if you apply a
magnetic field.
e-
-
e
42. Animated Science
2018
Radiation and Electrical or Magnetic Field Effects
-
2+
Alpha radiation has a +2 charge
but a RAM of 4 so is only weakly
deflected. Q/M = + 0.5
Beta radiation has a –1 charge and a
small mass so is strongly deflected
(1/1840 RAM) Q/M = -1840
Gamma
radiation has
no mass or
charge so it is
not deflected.
When radioactive particles enter electric
fields the charged particles can be moved
by the fields. Electrically charged plates
attract oppositely charged particles
according to charge/mass ratio.
- - - - - - - - - - - - - - - -
+ + + + + + + + + + + +
Charged particles act as if they are
a flow of current in a magnetic
field (+ to – ) and field N->S into
the page. (Y11 – Triple)
B
I
F
-
2+
x = Field into the page NS
43. Animated Science
2020
Alpha & Protons
This picture shows the tracks produced
by an alpha particle and a proton in a
strong magnetic field.
Which track was made by the proton
and which by the alpha particle?
Well think about charge to mass
ratios…
Alpha - > +2/4 = +0.5
Proton -> +1
Electron -> 1/ (1/1840) = -1840
Alpha
Proton
Electron
NB: If equal charges move at the same speed through the same magnetic field if one of
them has more mass it will have a larger radius of curvature because it has a greater mass
its inertia is greater and thus its direction is 'more difficult' to change. This is why the
electron moves more than the proton.
44. Animated Science
2021
Guess the field?
𝐹 =
𝑚𝑣2
𝑟
= 𝐵𝑞𝑣
𝑟 =
𝑚
𝑞
𝑣
𝐵
𝑞
𝑚
=
1
𝑟
𝑣
𝐵
𝑞
𝑚
∝
1
𝑟
⋅ 𝑐𝑜𝑛𝑠𝑡
As the q/m ratio increases i.e.
beta, the radius of curvature
reduces.
Work it out for a
beta, alpha,
gamma, pion (+)
46. Animated Science
2018
Geiger Muller Tube / Detectors
This rock is radioactive. It must
contain at least one unstable
isotope and as this isotope decays it
emits nuclear radiation.
The ratemeter or scaler clicks as it
detects the radiation and gives us a
reading in counts per second.
The blue badge contains a piece of
photographic film when it is
exposed to radiation the film, which
starts white, is blackened. The
darker it gets the more radiation has
fallen on it. We would wear one of
these to show us if we have
received too much radiation.
https://www.youtube.com/watch?v=M2-
7I8FnZ6g – GM Tube Nat History Museum
47. Animated Science
2021
Mica - Silicates
The silcate group is complex with
many forms making up 90% of
the crust of the earth. Mica
shown here has as an amazing
ability to cleave into thin parallel
sheets.
Used in electrical components,
isinglass, atomic force microscopy
and micrometer-thin sheets
which are relatively transparent
to radiation. It is therefore
commonly used as a window on
Geiger-Müller tubes.
Human use of mica dates back to
prehistoric times and has been
used in many civilisations over
the ages.
X2Y4-6Z8O20(OH,F)4
X is K, Na, or Ca or less commonly Ba, Rb, or Cs;
Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li,
Z is chiefly Si or Al, but also may include Fe3+ or Ti.
48. Animated Science
2018
Geiger Muller Tube in Detail...
mica window
collision & ionisation
radiation
The detector is a metal tube filled with gas. The tube has a thin wire down the
middle and a potential difference (400-450V) between the wire and the casing.
It is very good at detecting alpha and beta, not as good at detecting gamma due to
the low ionisation produced.
When the radioactivity enters the tube, it ionises the gas in the tube. This
produces a pulse of current which is amplified and passed to a counter or scaler.
The Argon contains
a little bromine to
act as a quenching
agent and prevent
continuous
discharge.
Argon gas
400V
0V
0V
Scalar Counter
51. Animated Science
2018
Lesson 3 Worksheet - Background Radiation…
Background radiation from human activity includes:
• waste products from hospitals
• waste products from nuclear power stations and other industries
• manufactured radioisotopes.
The three types of nuclear radiation have different penetrating powers and
abilities to ionise particles they hit. The penetrating power of the three
types of ionising radiation.
Gamma rays are the most penetrating, able to penetrate through several
metres of concrete or several centimetres of lead, but they are the least
ionising.
Beta particles can travel a few metres in air and can be stopped by
aluminium about 3 mm thick.
Alpha particles are the least penetrating, and can be stopped by a few
centimetres of air or a few sheets of paper, but are the most ionising.
Radiation dose is measured in sieverts (Sv) or Jkg-1.
It is considered safe to use alpha emitters in smoke
detectors because they are easily stopped by the air.
Therefore, alpha sources are the safest to use outside
the body. However, inside the body, the situation is
reversed.
Alpha particles have the largest mass and the highest
charge, so they have the highest ionising power. They
can be thought of as the radioactive equivalent to
cannon balls with their huge charge and mass. If you
breathe in or swallow an alpha emitter, all of the alpha
particles are absorbed by your body.
Beta particles do less damage and gamma rays the least
because they are the least ionising.
1. Use the pie chart to list the sources of
background radiation in order, starting with the
highest.
2. What percentage of background radiation comes
from natural sources?
3. Suggest why background radiation varies a in
different areas and b at different times.
4. Describe the penetrating and ionising powers of
beta particles.
5. Which type of radiation can penetrate a few
centimetres of aluminium?
6. Explain why radon gas is considered to be a
significant hazard.
7. Suggest how the amount of radiation to which
pilots and cabin crew in aeroplanes are exposed
differs from the average person. Justify your
answer.
52. Animated Science
2018
Background Radiation Answers…
1 Radon and thoron from soil, rocks and building materials; gamma rays from rocks and soil; radiation from
living things and food; cosmic rays from outer space; medical; fallout from nuclear weapons testing and other
forms such as air travel; work related; nuclear power industry.
2 All of the forms of background radiation apart from medical, work related, nuclear fallout, nuclear industry
and air travel are natural. Therefore, the total percentage = 37 + 19 + 17 + 14 = 87 %.
3a The types of rock are different in different areas so some areas are exposed to more background radiation
than others.
3b For example, nuclear fallout will vary depending on which way the wind is blowing. Cosmic background
radiation increases when the sun is particularly active.
4 Beta particles can pass through a few metres of air and paper but they are stopped by a few mm of low
density metals such as aluminium. Beta particles are more ionising than gamma rays but are less ionising than
alpha particles.
5 Gamma radiation
6 Radon is an alpha emitter and alpha particles are very ionising and therefore dangerous if the inside of the
body is exposed to them. Radon is also a gas so you can breathe it in.
7 It is likely that they would receive a higher amount of radiation. Pilots and cabin crew spend much of the time
in the air at a higher altitude. The atmosphere will not have absorbed as much cosmic radiation at this altitude
so the pilots and cabin crew will receive more cosmic radiation than people who spend more time at ground
level
53. Animated
Science
2021
Mr D Powell
2021
Animated Science
2021
26.3 More on , ,
INSPIRE
C
I know some of the details
about , , and their main
properties/dangers
I can compare , , in terms of 6
key features in detail. & interactions
I can investigate the inverse square law
for a source
I can use a complex corrected equation for counts without help
and explain the nature of the analysis.
A
B
54. Animated Science
2018
Radioactive
Particle
Description Nuclear Equation
A part of the Radium nucleus breaks
off as 2 protons and 2 neutrons. It
leaves the nucleus and forms helium
ion, leaving a new atom Radon
A neutron inside the Carbon nucleus
“decay’s” and changes to become a
proton. Mass overall is unchanged
but it becomes Nitrogen (gaining a
free electron from space) and
emitting a high energy electron or
beta particle. (almost massless in
comparison 1/1840)
Iodine has just decayed via a beta or
alpha process. However, it is still
excited “*” with spare energy.
Sometime later the energy leaves in
the form of a gamma wave.
𝛼2
4
2
4
𝐻𝑒2+
88
226
𝑅𝑎 → 86
222
𝑅𝑛 + 2
4
𝐻𝑒2+
𝛽−
𝑒− 6
14
𝐶 → 7
14
𝑁 + −1
0
𝛽
𝛾
I
I 125
53
125
53
Nuclear Eq Examples….
55. Animated Science
2018
Decay Chains…. (Higher Challenge)
Decide whether each
decay in this decay chain
is alpha or beta decay
and discuss the correct
decay process on each
arrow in a pair. The first
one has been done for
you.
Second to this go on to
write at least 4 nuclear
equations for the chain,
so the changes to
protons, neutrons and
mass are clear.
A decay chain is a sequence
of nuclear equations that
shows how unstable nuclei
decay until a stable atom,
usually lead, is reached.
56. Animated Science
2018
Decay Chains…. (Higher Challenge)
Decide whether each
decay in this decay chain
is alpha or beta decay
and discuss the correct
decay process on each
arrow in a pair. The first
one has been done for
you.
Second to this go on to
write at least 4 nuclear
equations for the chain,
so the changes to
protons, neutrons and
mass are clear.
A decay chain is a sequence
of nuclear equations that
shows how unstable nuclei
decay until a stable atom,
usually lead, is reached.
https://www.youtube.com/watch?v=M3apSDAhkTY
57. Animated Science
2018
Pb-210
Po-214
Po-218
Pb-214
Rn-222
Ra-226
Th-230
U-234
Pa-234
Th-234
U-238
–
–
–
neutron number N
Main source of
naturally
occurring
radium, half-life
1600 yr. Radium
was discovered
by Marie Curie
and her husband
Pierre Curie.
146
144
142
140
138
136
134
132
130
128
126
124
Bi-214
Bi-210
Po-210
–
–
–
Pb-206 stable
half-life 4.5 109
yr
88 89 90 91
87
86
85
84
83
82
Pb Bi Po At Rn Fr Ra Ac Pa U
proton number Z
92
Th
Decay Chains .....
Decay chain from Th-232
142
140
138
136
134
132
130
128
126 Pb-208
Po-212
Tl-208
Pb-212
Bi-212
Po-216
Rn-220
Ra-224
Th-228
Ac-228
Ra-228
Th-232
–
–
–
–
neutron number N
87 88 89 90
86
85
84
83
82
81
Tl Pb Bi Po At Rn Fr Ra Ac Th
proton number Z
Radon gas, half-life 56 s,
from building materials is
an important part of the
natural background
radiation
Marie Curie, discoverer with
Pierre Curie of polonium,
named the element after her
native Poland
59. Animated Science
2018
British Museum Gebelein Man - Oldest Mummy found in the World!
We can use the half life of carbon to put a date
on a mummy.
The first video here is from Gebelein, Egypt,
Predynastic period, around 3500 BC which is
the oldest mummy ever found and is in the
British museum
The second video goes through the whole
process. You should know this for the exam.
There is also a flow chart on the next slide to
help you understand it
7
14
𝑁 + 𝑛 → 6
14
𝐶 + 𝑝
6
14
𝐶
𝑏𝑒𝑡𝑎𝑑𝑒𝑐𝑎𝑦
7
14
𝑁 + 𝑒−
https://youtu.be/8QnsA_1pEd8 - General Video
60. Animated Science
2018
Cosmic Rays or
neutrons hit a
Nitrogen (14) atom
The neutron is
absorbed
Carbon 14 is
produced
C14 decays by beta
minus
Half life is 5730
years
Electron emitted in
process
Living things
exchange
radioactive carbon
When you die
carbon in you is
fixed
This allows you to
date when you
died
We look at the
activity of the
sample and track
back!
Carbon Dating Flow Chart - Movie…
7
14
𝑁 + 𝑛 → 6
14
𝐶 + 𝑝
6
14
𝐶
𝑏𝑒𝑡𝑎𝑑𝑒𝑐𝑎𝑦
7
14
𝑁 + 𝑒−
Mummy Carbon Dating…
https://youtu.be/omYFF_tpZSw
61. Animated Science
2018
Carbon Dating
7
14
𝑁 + 𝑛 → 6
14
𝐶 + 𝑝
6
14
𝐶
𝑏𝑒𝑡𝑎𝑑𝑒𝑐𝑎𝑦
7
14
𝑁 + 𝑒−
Here is a good example of capture of a
neutron into the nucleus followed by
decay back again via a beta minus
process.
C
C
C
C
C
10
11
12
13
14
6
6
6
6
6
9
8
7
6
5
4
N
Z
5 6 7 8 9
62. Animated Science
2018
Decay Modes of Carbon – Key ones in Blue – Simple Version
symbol Z N half-life decay mode
daughter
isotope
12C 6 6 Stable
13C 6 7 Stable
14C 6 8 5730 years β− 14
N
15C 6 9 2.449 s β− 15
N
You can see how Carbon 14 and 15 both have beta decay to become stable. They
are trying to get closer to be stable like Carbon 13 and 14.
Carbon 14 is used in carbon dating due to its very long half life and abundance in
our bodies.
63. Animated Science
2018
Decay Modes of Carbon – Key ones in Blue – (Extension Version)
symbol Z N half-life decay mode
daughter
isotope
10C 6 4 19.290 s β+ 10
B
11C 6 5 20.334 min β+ 11
B
12C 6 6 Stable
13C 6 7 Stable
14C 6 8 5730 years β− 14
N
15C 6 9 2.449 s β− 15
N
You can see how Carbon 14 and 15 both have beta decay to become stable. They
are trying to get closer to be stable like Carbon 13 and 14. Carbon 14 is used in
carbon dating…
AS Physics will cover beta plus decay which is almost a reverse of beta minus
decay.
64. Animated Science
2020
Neutrino
Neutrinos are elementary particles that travel close to the
speed of light, lack an electric charge, are able to pass
through ordinary matter almost undisturbed and are thus
extremely difficult to detect. Neutrinos have a minuscule,
but nonzero mass. They are usually denoted by the Greek
letter (nu)
Created as a result of certain types of radioactive decay or
nuclear reactions such as those that take place in the Sun,
in nuclear reactors, or when cosmic rays hit atoms.
There are three types, or "flavours", of neutrinos: electron
neutrinos, muon neutrinos and tau neutrinos (not needed
for AQA; each type also has an antimatter partner, called
an antineutrino.
Are generated whenever neutrons change into protons or
vice versa, the two forms of beta decay. Interactions
involving neutrinos are generally mediated by the weak
force (rad decay)
𝜈𝑒
𝜈𝑒
65. Animated Science
2021
The Neutrino..
These lines represent the energy
levels each beta radiation was giving
out
The gap between the energy of the beta
radiation and the constant energy value is
the amount of energy the neutrino must
take up to agree with the ‘conservation of
energy’ laws.
How where they first predicted?
Wolfgang Pauli saw that beta radiation did not give off any
fixed energy value, he suggested the Neutrino was emitted
with the high energy electron to keep the energy level in Beta
decay as shown below;
𝜈𝑒
68. Animated Science
2020
Reference… • At each vertex there must
be equal charge into and
out of the point of
interaction.
• Consider each vertex on
its own.
• Each vertex will either
cancel, carry through +1
or -1 charge
• When a lepton is released
an anti-lepton is required
to balance lepton number
• All diagrams relate to a p
or n interacting with
lepton
• Direction of the boson is
important to work out the
vertex rules!
- Decay
Electron
Capture
+ Decay
Antineutrino-
proton collisions
Proton-Electron
Collision
Neutrino-neutron
collision
High energy!
Low energy!
69. Animated Science
2021
Gamma and Inverse Sq Law
𝐶 − 𝐶0 =
𝑘
𝑑 + 𝑑0
2
We must find the source centre for inverse sq
law to work correctly.
70. Animated Science
2021
Corrected count rates & distances....
d
d0
𝐶 − 𝐶0 =
𝑘
𝑑 + 𝑑0
2
We must find the
source centre for
inverse sq law to
work correctly.
𝑑 = 𝑘 ⋅
1
𝐶 − 𝐶0
− 𝑑0
y
m
https://youtu.be/xq8V0Q9WtEs
https://youtu.be/5F_qDx7HYAs
71. Animated Science
2021
Example Data
Colonel Frank Seely 2014
d / m c / minute Background
0.179 91 125 in 500s
0.166 106
0.153 114
0.137 139
0.122 187
0.101 214
0.084 288
0.069 397
0.027 1462
81. Animated
Science
2021
Mr D Powell
2021
Animated Science
2021
26.4 The Dangers of
Radioactivity
INSPIRE
C
I can explain why ionising
radiation is harmful.
I can compare what factors determine
whether , , are the most
dangerous.
I can explain how exposure to ionising
radiation can be reduced.
I can present information from around the world to explain the
dangers from radiation (3 mins presentation)
A
B
82. Animated Science
2018
Many of the servicemen who watched the first nuclear explosion in the Arizona
desert then went on to develop cancers. Their bodies were contaminated by
radioactivity.
Radioactive contamination Is the unwanted presence of materials containing
radioactive atoms. They can be on surfaces or within solids, liquids and gases.
Including in the human body and on the skin.
Radioactive materials In the environment, whether natural or artificial, can
expose people to risks. Contamination occurs when people swallow or breathe In
radioactive materials. Radioactive materials can also enter the body through an
open wound or be absorbed through the skin. Some radioisotopes may be
absorbed by specific organs, where it is possible they could cause cancer or
mutations of genes.
The type and amount of radiation emitted affect the level of hazard The most
unstable nuclei have the shortest half-lives. However, they can give out a lot of
radiation in a very short time. Unstable nuclei with long half-lives may give out
much smaller amounts of radiation, but this will build up over a long period of
time.
How the type of radiation affects the level of contamination The level of
contamination is affected by two things: the penetrating power of the radiation
and its ionising power. These are very different and have contrasting effects
A medical tracer is a radioisotope that Is put into the body. either by injecting it or
eating it. The tracer can be used to: monitor the functioning of internal organs or
check for a blockage in a patient's blood vessel. When using radioisotope tracers,
a background count should be taken several times first, in the absence of the
radioisotope, and an average background count should be calculated. This value is
then subtracted from readings obtained with the radioisotope.
Hazards and Uses of Radiation – Worksheet GCSE The tracer needs to produce nuclear radiation that can pass
from inside the body to the outside so It can be detected. It also
needs to be weakly ionising so that it does not do too much
damage to the body.
Tracers move around the body in the patient's blood. As the
tracer emits radiation, we can monitor where the blood flows
to. Therefore blockages in the blood flow can be detected. Once
the patient has been monitored, the tracer is no longer needed.
If the tracer remained in the body it would continue to damage
the cells without being of any use. Therefore it is important that
we use tracers with a short half-life
Questions
1. What is radioactive contamination?
2. Why is contamination a hazard?
3. State the least hazardous form of radiation when the
contamination is inside the body.
4. Explain why contamination by an alpha particle emitter is
much more dangerous if it gets inside the body.
a) .. Why is it important to take a background count?
b) Why should you take several readings of the
background count?
6. A doctor has a choice of three radioisotopes that can be
used as tracer. The half-lives of the isotopes are 6 seconds.
6 hours and 6 days. Explain which isotope the doctor should
use
7. Suggest what type of source of nuclear radiation is the most
suitable for a tracer. Explain your answer.
8. Suggest how a tracer could be used to check for a blockage
in patient's blood vessel.
83. Animated Science
2018
Lesson 6 Hazards and Uses of Radiation - Worksheet
1 When a radioactive material is somewhere
where it isn’t wanted.
2 Radioactive materials produce ionising
radiation which is harmful to health. Ionising
radiation can kill cells and can cause cancer.
3 Gamma (since it has the weakest ionising
power)
4 Alpha particles are very ionising which means
that they are more likely to kill cells or cause
cancer. However, they are not very penetrating
so if they are outside the body they can’t get in
and cause the damage.
5a You need to make sure that your
measurements are a true measure of the activity
of the tracer rather than that of the background
radiation.
5b Background radiation is random and its
activity can be higher at some times than at
others. You need to use an accurate average.
6 The isotope with the half-life of 6 hours. 6
seconds would mean that the isotope has
decayed to unmeasurable levels before the
tracer can be monitored and 6 days would mean
the patient would remain radioactive long after
the procedure had taken place which would add
unnecessary risk.
7 A gamma emitter. Gamma radiation has the
weakest ionising power so it does the least harm
to the body. It is also the most penetrating so it
can pass from the inside of the body where the
tracer is, to the outside where it can be
detected.
8 Inject the tracer into the blood. Leave enough
time for the tracer to be carried by the blood
through the body. Examine the patient with a
gamma camera. If there is a large signal at a
particular place in the vessel then it is likely that
there is a blockage in that place.
85. Animated Science
2021
Radiation – Badges….
To monitor gamma rays or x-rays, the
filters are metal, usually aluminum or
copper.
To monitor beta particle emission, the
filters use various densities of plastic.
It is typical for a single badge to contain a
series of filters of different thicknesses
and of different materials.
The precise choice may be determined
by the environment to be monitored.
The use of several different thicknesses
allows an estimation of the
energy/wavelength of the incident
radiation.
https://youtu.be/QKf0zrmpoik - gamma
https://youtu.be/R-N0pb40ZWI - general
86. Animated Science
2021
Radiation – Badges….Extension Details…
Films badges are effective at measuring gamma rays, x-rays, beta particles, and neutrons. It consists of two
components: a film with an emulsion coating and a housing to contain that film.
Often, multiple films with different emulsion sensitivities, or a single film with multiple layers of emulsion, are
used to discern various thresholds of radiation dosage.
The film holder or badge is typically metal when the film badge is monitoring for gamma or x-rays, or plastic if
monitoring for beta particles.
The badge prevents light, liquids, and vapours from entering the protective envelope and compromising
results.
To determine dosage, the badge uses up to five radiation-filtering materials to attenuate radiation at different
sections of the film.
These materials include aluminium, copper, lead/tin, plastic, as well as an open window that offers no
shielding.
The level of radiation is measured by comparing the results after ionizing radiation has passed through the
different filters and darkened the film at different rates.
The film emulsion contains silver bromide, therefore resulting in a higher atomic number on the film than
what is received by biological tissues. An algorithm accounts for the different rates of film exposure and
correlates it to actual exposure dosages. Typically these computations are processed by a commercial
laboratory.
Film also create a permanent exposure record, can determine the energy levels of photons, and can measure
multiple types of ionizing radiation.
87. Animated Science
2018
Irradiation is where an object is exposed to
nuclear radiation, but it does not become
radioactive itself.
The international Radura logo is used to
show a food has been treated with ionising
radiation so bacteria are killed from the
surface of the food and the food lasts
longer on the shelf. It is not
“contaminated”
What is the difference between irradiation and contamination?
Contamination is where materials become
radioactive.
For example nuclear fallout is the
distribution of radioactive
contamination by a nuclear explosion.
Contamination may occur from radioactive
gases, liquids or particles being ingested
into your body or on the surface. Task:
1. Compare the two key ideas.
2. Make a note of the definition &
differences in your book
3. Use the internet to help you write
your notes in detail (if you have
time)
4. What is the Radura logo and why
is it use?
88. Animated Science
2018
Ionisation (Alpha?)
Nuclear radiation is dangerous. It is dangerous
because it damages the molecules in our cells
so that they don't work properly. The cell may
die. (see the plant video If you are exposed to
a lot of radiation then a lot of cells may be
killed and you would be very ill.
The molecules are damaged because atoms
which make up the molecule are ionised. This
means that when the radiation bashes into
them it knocks off electrons from the outside
of the atom. They become ions. One alpha or
beta particle has enough energy to cause
thousands of ionisations.
You might think that alpha was the least
dangerous because it can't even get through
paper. When handled carefully it is safe.
However, It is most dangerous when it gets
inside your skin or body. The cellular damage
often causes the cancer or mutation.
https://www.youtube.com
/watch?v=08Xd2xqN4wQ
Gamma Damage
89. Animated Science
2018
Uses - Sterilising Food
Gamma rays are used to kill bacteria, mould and insects in
food. This can be done even after the food has been
packaged. It can affect the taste, but supermarkets like it
because it lengthens the shelf life.
Gamma rays are also used to kill bacteria on hospital
equipment. It is particularly useful with plastic equipment
that would be damaged by heat sterilisation.
Gamma Source
unsterilised sterilised
Make a note of
how this works in
your book, include
a diagram to help
you explain how it
works…
91. Animated Science
2018
Lesson 7 Irradiation OR Contamination
Some foods are irradiated, which kills microorganisms living on
them. The foods can then be kept much longer before they go off.
Irradiation is where an object is exposed to nuclear radiation. The
exposure can originate from various sources. including natural
sources and background radiation.
Some things are Irradiated with X-rays or gamma rays for
therapeutic purposes or to sterilise food. Gamma rays are
sometimes used in hospitals to sterilise food for seriously ill
patients. Irradiation is also used by some supermarkets to kill
bacteria on fresh food so that the food stays fresh for longer.
Nuclear radiation causes ionisation. The cells in our bodies can also
be changed by radiation. DNA can be changed by nuclear radiation.
This is called mutation. Sometimes when a cell mutates it divides in
an uncontrollable way- This can lead to cancer. Low levels of
irradiation have little effect on the health of humans. However. if
people are exposed to high levels of irradiation it is important to
consider the radiation risks for these people and their descendants.
Damage to a person's cells is called damage by irradiation. shows
the effects, which are cell death, accurate repair or mis-repair
causing mutation of genes. Suitable precautions must be taken to
protect against any hazard the radioactive source used in the
process of irradiation may present.
The first scientists to investigate nuclear radiation were unaware of
its effects on their health. and many died as a result. When the first
atomic bombs were exploded, scientists were not aware of the
potential effects on health They discovered that nuclear radiation
can have long term effects, causing genetic mutations which affect
subsequent generations. It is important for the findings of studies
into the effects of radiation on humans to be published. This means
that scientists can find out about what other scientists are doing.
They can try to repeat experimental results and check the results,
which Is called peer review
Questions
1. Describe what is meant by irradiation.
2. Compare the level of irradiation we get from food with the irradiation from
the air.
3. list the three possible effects of irradiation on human body
4. Why could irradiation have an effect on somebody's grandchildren?
5. Explain the difference between irradiation and contamination.
6. Explain why experimental findings should be checked by peer review.
7. Some pigeons were found to be contaminated with caesium 137 a
radioisotope of caesium with a half life of about 30 years. They were almost
certainly irradiated too. Suggest why the pigeons were at greater risk from
contamination than from irradiation
92. Animated Science
2018
Lesson 7 Irradiation OR Contamination - Answers
1 Irradiation is when you expose an
object to nuclear radiation.
2 We receive much more irradiation
from the food than from the air (it’s
about 500 times more).
3 Accurate repair, cell death, misrepair
4 If a sperm cell or an egg cell is
misrepaired then this change of
genetic material could be passed onto
offspring.
5 Irradiation is exposing someone to
nuclear radiation. Contamination is
when radioactive material is actually
present on the person (which will
continue to irradiate them).
93. Animated Science
2018
Lesson 7 Irradiation OR Contamination - Answers
6 The people doing the
experiments might have made
mistakes. If other people carrying
out an experiment agree with the
findings, then the findings are
more likely to be true.
7 Once the pigeons move away
from something that is irradiating
them then they are no longer
exposed to the radiation. However,
if they are contaminated with
radioactive material then they will
continue to be irradiated for as
long as the material in them
remains radioactive. This is much
more likely to cause them serious
harm. Pigeons live for 6 years so
spend most of their life with a large
activity inside them!
94. Animated Science
2018
Cancer – Extra Details
What would happen if nobody died? Imagine also that the people
alive kept having children. What would happen to the planet?
Most of the cells in our body are only supposed to last for a certain
time. A months or a few years at the most. Their life cycle is
controlled by genes in the nucleus of the cell. Sometimes these
genes don't work properly and the cells multiply rapidly and don't
die. This is what cancer is. It is very hard to fight cancer because it is
our own body cells which are the problem so our immune system
doesn't recognise them as a threat.Cancer may be caused by a
number of things;
• Some people inherit faulty genes off their parents which increase
the chances of them getting cancer at some time in their life.
• Some chemicals can cause cancer. There are lots of these in
cigarette smoke such as polonium an alpha emitter.
• Ionising radiation can cause cancer if it damages the molecules in
our genes.
• The more radiation you are exposed to the greater the risk of
cancer.
95. Animated Science
2018
Dealing with Radioactive Waste – Reducing the Risks
Category Examples Disposal
Low level
Contaminated
equipment,
materials and
protective
clothing
Put in drums and surrounded
by concrete, and put into clay
lined landfill sites
Intermediate
level
Components
from nuclear
reactors,
radioactive
sources used in
medicine or
research
Mixed with concrete and put in
a stainless steel drum in a
purpose-built store
High level
Used nuclear
fuel and
chemicals from
reprocessing
fuels
Stored underwater in large
pools for 20 years, then placed
in storage casks in purpose-
built underground stores
where air can circulate to
remove the heat produced.
High level waste decays into
intermediate level waste over
many thousands of years.
There are several different
categories of nuclear waste.
Low-level radioactive waste,
such as contaminated gloves,
can be disposed of in landfill
sites.
Higher level waste, which may
be dangerously radioactive, is
more difficult to dispose of.
It can be reprocessed to extract
nuclear fuel or encased in glass
and left deep underground.
Waste has to be safely
transported from the power
stations and usually this is by rail
or truck. However, routes have
to be carefully planned and
escorted to stop accidents or
theft.
96. Animated Science
2018
Storing & Transport Nuclear Waste..
https://youtu.be/HmMzEjo5Pxk - Transport
https://youtu.be/aoy_WJ3mE50 - Storage
97. Animated Science
2021
Production of X-Rays v Gamma Emission
X-rays and gamma rays are both ionising
and have similar wavelengths
X-rays are manufactured by an x-ray
machine. Where a hot cathode emits
electrons that are attracted to a tungsten
anode.
When the fast-moving electrons hit the
metal target, most of their kinetic energy is
transferred to heat but some is transferred
to x-rays.
This machine allows the energy and
intensity of the x-rays to be controlled.
Gamma rays, on the other hand, are given
out by radioactive materials from a nucleus.
This process is totally random and so cannot
be controlled as easily as x-rays.
Task: Compare the two ideas?
98. Animated Science
2018
Cat Scanners
CCDs...A CCD is a charge-coupled
device. Modern X-ray machines use CCDs
instead of photographic film. The images are
formed electronically, allowing them to be
recorded and stored more easily than the
images from photographic film.
CT scans...Traditional X-ray imaging gives a
two-dimensional (2D) view of the body from
one angle. This can result in detail being
obscured by other structures in the
body. Computerised tomography (CT) scans
involve taking a range of X-ray images from
various positions.
These are processed by a computer to build
a three-dimensional (3D) image. This image
can be manipulated in order to see the
structures within the body at different layers
and from different points of view. This lets a
doctor gain a much greater insight into what
is wrong with a patient.
Task: Read this then
explain the difference
between a CT Scan and
X-Ray to another
person?
https://youtu.be/l9swbAtRRbg
99. Animated Science
2018
Precautions when using X-rays
Patients are limited to the number of X-rays they are
allowed to have so their bodies are not exposed to too
much radiation.
X-ray machines also produce relatively low energy X-rays,
which reduce the risk of them damaging human tissue.
Hospital staff are also at risk from repeated exposure to
low levels of X-rays. Shielded walls containing lead are
built into all X-ray rooms to protect people outside the
room. They have warning signs to show when the room
is in use so that people do not enter.
Only trained specialist staff - called radiographers - are
allowed to use X-ray machines. They routinely leave the room,
or stand behind a screen containing lead, whenever X-ray
machines are in use.
In situations where radiographers cannot stand behind a
screen, they wear lead aprons which act as a protective layer
of clothing.
100. Animated Science
2018
Contrast Mediums - https://youtu.be/nVxBuSjSpEs
Barium sulfate (BaSO4) is a salt of barium (Ba), a metallic
chemical element with atomic number 56. Barium is
considered one of the heavy metals. Unlike barium and many
of its other salts, barium sulfate is insoluble in water and
therefore very little of the toxic barium metal is absorbed
into the body.
Barium can be mixed into high-density or low-density
suspensions. Both suspensions typically attenuate x-rays
more than water-soluble contrast.
High-density barium is preferred over water-soluble contrast
for fine-detail evaluation of the gastrointestinal system (e.g.
evaluation for early changes from Crohn disease).
Suspensions created for CT or CAT Scans use are very low
density.
Due to its insolubility in water, barium sulfate contrast media
are supplied as fine particles of the barium sulfate suspended
in water. Often artificial flavourings are added to make the
mixture more palatable.
Iodine based (brain)
Barium based (colon)
101. Animated Science
2018
Ionising effect of X-rays – Risks of Treatments
The ionising properties of X-rays mean that they can damage the DNA in cells. The
ionising effect of X-rays is more damaging to actively dividing cells in the body.
Low doses of X-rays may cause cancer - whereas high doses may kill cancerous cells.
Cancer treatment
Cancer is a disease in which cells divide uncontrollably because of changes in their
DNA, forming tumours.
One method of treating cancer is to direct high energy X-rays at the tumours. This
causes so much damage to the cancerous cells that they die. This treatment is
called radiotherapy.
102. Animated Science
2018
Brachytherapy is a treatment where we use radiation to destroy a tumour. The treatment of
cancer, especially prostate cancer can be achieved by the insertion of radioactive implants
directly into the tissue.
This is particularly effective as the rods inserted are focused on the tumour entirely so very
little radiation leaks out into healthy tissues.
This means the success rates are much better than the normal gamma radiation treatments
which are applied externally and focus on a point. These treatments result in tissue damage
and a higher dose of radiation in the patients body.
Brachytherapy – Extension Ideas…
103. Animated Science
2018
Mammograms
Breast screening aims to find breast cancers early. It uses
an X-ray test called a mammogram that can spot cancers
when they're too small to see or feel.
But there are some risks of breast cancer screening that
you should be aware of.
As the likelihood of getting breast cancer increases with
age, all women aged from 50 to their 71st birthday who
are registered with a GP are automatically invited for
breast cancer screening every 3 years.
Breast screening involves having an X-ray (mammogram)
at a special clinic or mobile breast screening unit. This is
done by a female health practitioner. Your breasts will be
X-rayed 1 at a time. The breast is placed on the X-ray
machine and gently but firmly compressed with a clear
plate. Two X-rays are taken of each breast at different
angles. 95% of cancers can be picked up this way.
https://www.nhs.uk/
conditions/breast-
cancer-screening/
104. Animated Science
2018
Cancer cells can be destroyed by exposing the affected area of the body to extremely large
amounts of radiation. This process is called radiotherapy. Cobalt-60 emits gamma rays and Is
widely used to treat cancers. X-rays are often preferred to gamma rays because:
• X-rays are only produced when needed.
• The rate of production of rays can be controlled.
• The energy of the X-rays can be changed.
• You cannot change the rate of production or energy of the gamma rays emitted from a
particular source.
High-powered X-rays can be used in radiotherapy to destroy a tumour inside the body. A dose
large enough to destroy the tumour would also destroy the healthy tissue it passed through. Two
techniques are commonly used to protect healthy tissue:
• The source is slowly rotated around the patient with the tumour at the centre of the circle.
• The source is used in three different directions around the target area.
Both techniques minimise the side effects of the X-rays on tissues that are not cancerous. In each
case, the beams Intersect at the centre of the tumour
In brachytherapy a small sealed radioactive source or seed placed in the tumour itself, to give a
high dose of radiotherapy directly to the tumour but a much lower dose to the surrounding tissues.
Brachytherapy is mainly used to treat cancers In the prostate gland, cervix and womb. It is
sometimes given in addition to external radiotherapy. Iodine-131 an artificially produced
radioisotope that can be used to investigate problems with the thyroid gland as it can be absorbed
by the organ.
Questions….
1. What do X-rays and gamma rays have in common?
2. Describe the uses of manufactured radioisotopes.
3. Give two advantages of using X-rays rather than gamma rays.
4. How is brachytherapy different to the usual form of radiotherapy?
5. Suggest some possible problems associated with brachytherapy.
6. Explain why most radioisotopes used in brachytherapy are beta emitters.
X-rays are used in a CAT (computerised axial
tomography) scan to produce cross-sectional
images of a part of the body. They can be used
to produce a 3D image of the inside of the body.
Using X-rays and gamma radiation in medicine
which have a similar wavelength. They are also
both ionising radiation but they are produced in
different ways. Gamma rays are emitted by
radioisotopes, whereas X-rays are produced by
X-ray machines and not emitted from the
nucleus of atoms. X-rays and gamma rays are
used to diagnose problems and treat them.
They can be used to explore internal organs and
bones. and to control or destroy cancerous cells
The radioisotopes used In medicine must: emit
gamma rays, have a suitable half-life and not be
toxic to humans.
Manufactured radioisotopes are produced with
properties that make them Ideal for specific
uses. Sometimes radioisotopes that emit beta
particles are also used.
Uses of Radiation in Medicine
105. Animated Science
2018
Uses of Radiation in Medicine – Answers…..
1 They are both types of electromagnetic
waves.
2 Many manufactured radioisotopes are
used in medicine. Some of these are used
to destroy cancerous cells from the
radiation they produce; others are used as
tracers to help diagnose problems with a
patient in order to treat them.
3 X-rays are only produced when needed.
You can control the energy of the x-rays
that you produce.
4 Bracytherapy uses the radioactive source
right next to (or inside) the tumour rather
than the radiation coming from outside the
body.
5 You need to make sure that you can
extract all of the radioactive source so you
don’t contaminate the patient. Placing the
radioactive source near the tumour might
need invasive surgery which can lead to
problems with infection.
6 Alpha particles wouldn’t penetrate very
far into the tumour (and probably wouldn’t
even be able to leave the protective
casing).
Many gamma rays would pass through the
tumour so there would be a large dose
applied to tissue outside of the tumour.
Beta particles would penetrate into the
tumour and deposit most of their energy
within the tumour. Therefore, the tumour
would get the biggest dose with a beta
emitter.
106. Animated Science
2018
Common Radiation Units...
Quantity Name Symbol Unit Year System
Activity (A)
curie Ci 3.7×1010 s-1 1953 non-SI
becquerel Bq s−1 1974 SI
Dose
equivalent
(H)
röntgen
equivalent
man
rem 100 erg·g−1 1971 non-SI
sievert Sv J·kg−1 1977 SI
Activity is the number of decays per second and is the “raw” measure of the
“decays per second”.
Dose is a measure of harm that a particular procedure does to the patient as it
takes into account how much energy is deposited into the body per kg so allows a
comparison to take place.
You need to use Bq and understand the ideas behind Sv which may appear in
questions!
You may see mSv or milli Sv which is 1x10-3Sv
107. Animated Science
2021
Sievert Extra Details
The sievert (symbol: Sv) is the SI derived unit of dose equivalent. It attempts to reflect
the biological effects of radiation as opposed to the physical aspects, which are
characterised by the absorbed dose, measured in gray. It is named after Rolf Sievert, a
Swedish medical physicist famous for work on radiation dosage measurement and
research into the biological effects of radiation. 1 Sv = 1 J/kg = 1 m2/s2 = 1 m2·s–2
Frequently used SI multiples are the millisievert (1 mSv = 10–3 Sv) and microsievert (1 μSv
= 10–6 Sv).
The millisievert is commonly used to measure the effective dose in diagnostic medical
procedures (e.g., X-rays, nuclear medicine, positron emission tomography, and computed
tomography). The natural background effective dose rate varies considerably from place
to place, but typically is around 2.4 mSv/year. For acute (that is, received in a relatively
short time, up to about one hour) full body equivalent dose, 1 Sv causes nausea, 2-5 Sv
causes epilation or hair loss, hemorrhage and will cause death in many cases. More than 3
Sv will lead to LD 50/30 or death in 50% of cases within 30 days, and over 6 Sv survival is
unlikely. (For more details, see radiation poisoning.)
The collective dose that a population is exposed to is measured in "man-sieverts"
(man·Sv).
108. Animated Science
2021
Prep Task…
Topic Student
Three Mile Island
Chernobyl
Fukashima
Hiroshima
Nagasaki
Sellafield
Greenham Common
Task…
Create a 3-5 minute
presentation for data projector
on the topic given.
Research…
• Issues around radiation
leaks?
• What is present there?
• Good points?
• Background Radiation
Include a simple hand-out for all
students in your class
Ensure you have it on memory
stick or accessible!
