Safe Working With
Ionising Radiation
Revised January 2012
John Sutherland,
University Safety and Radiation Protection
Officer
Remember
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otherwise you will need to re-attend!!
 Handout - also downloadable from Safety
Office Web Page
Programme
 What is radiation?
 How is it measured?
 Biological harm
 Doses into perspective
 Legislation
 Unsealed work
 X-ray/Sealed - Harry Zuranski, Safety Office.
Objectives
 Foundation for Training in School
 Understand principles

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
radiation types and effects
biological effects
relative risk
legislation
university arrangements
 Safe Practice
Atomic Structure
X
a, B, Y
neutron
Isotopes
•Variable neutron number
•Unstable nuclei transform
•Ionising radiation emitted
Ionisation
•Energy transfer
•Enough energy ~ 13+ eV
Half - life
Isotope
Half-Life
Tritium
Carbon 14
Sulphur 35
Phosphorus 33
Phosphorus 32
Iodine 125
12.4 y
5730 y
87.4 d
25.6 d
14.3 d
60.1 d
Types of Radiation
 Video
Types of Radiation
 Alpha
 From heavy nuclei (e.g. Americium 241)
 Helium nuclei (2P+2N)
 1500 ionisations
 Dangerous internally
 Easily shielded as very large particles
 Sheet of paper or plastic film
 Small distance of air
 Dead outer layer of skin
Types of Radiation
 Beta Particles (B)
 High speed electrons from nucleus
 Identical to orbital electrons
 Neutron
Proton + B Energy dependent penetrating power
3H - 18.6 KeV
 14C - 156 KeV
 32P - 1.71 MeV
Rule of thumb for maximum range of beta particles
 4 metres in air per MeV of charge
 P32 can travel up to 7 m in air but 3H only 6mm!
Easily shielded with perspex, higher energy needs greater
thickness
 10 mm will absorb all P32 betas
Cannot reach internal organs
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Types of Radiation
 Bremsstrahlung

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
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X-radiation resulting from high energy ß particle
absorption in high density shielding, e.g. lead.
Risk with 32P and similar high energy ß emitters.
Shield ß with lightweight materials such as perspex.
Very large activities can still produce some
Bremsstrahlung from perspex - supplement perspex
with lead on outside to absorb the X-rays.
Types of Radiation
 Gamma Radiation (Y)
 Electromagnetic radiation
 Emitted from nucleus
 Readjustment of energy in nucleus following a or ß
emission
 Variable energy characteristic of isotope
 Highly penetrating




5 - 25 cm lead
3m concrete
Can reach internal organs
Can pass through the body
Types of Radiation
 X-Radiation

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
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Similar to gamma but usually less energetic
Originates from electron cloud of the nucleus
Produced by machines - can be switched off!
Also produced by some isotopes


Iodine-125 produces both gamma and x-rays
Broad spectrum of energy
Types of Radiation
 X-rays
 Incident radiation ejects electron
 Outer electron fills gap
 X-ray energy = difference between
orbital energy levels - characteristic
 Bremsstrahlung also produced
Types of Radiation
 Neutrons
 Large, uncharged, physical interaction.
 Spontaneous fission (Californium 252)
 Alpha interaction with Beryllium (Am-241/Be)
 Shield with proton-rich materials such as hydrocarbon
wax and polypropylene.
 Americium/Beryllium sources are used in neutron
probes for moisture or density measurement in soils
and road surfaces etc. These also emit gamma
radiation.
Units of Radiation
 SI units Becquerel, Gray, Seivert

replaced Curies, Rems, Rads
 Activity
 Dose



absorbed
equivalent
committed
Units of Radiation - activity
 Quantity of r/a material
 Bequerel (Bq; kBq; MBq)


1 nuclear transformation/second
3.7 x 1010 Bq = 1 Curie
 Record keeping
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Stock, disposals
Expt protocols
Units of Radiation - dose
 Absorbed - Gray (Gy)
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Radiation energy deposited
1 Gy = 1 joule/kg
 Dose Equivalent - Seivert (Sv)
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modified for relative biological effectiveness
beta, gamma, X = 1
alpha, neutrons = 10-20
Units of Radiation - committed
 Internal
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
irradiation until decay or elimination
radiological and biological half-lives
data for 50-year effect
 Annual Limit on Intake (ALI)
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
limit on committed dose equivalent
quantity causing dose limit exposure
Exposure to Ionising Radiation
 Environment
 Naturally occurring radioactive minerals remaining from
the very early formation of the planet.
 Outer space and passes through the atmosphere of
the planet – so-called cosmic radiation.
 Man-made
 medical treatment and diagnosis.
 industry, primarily for measurement purposes and for
producing electricity.
 fallout from previous nuclear weapon explosions and
other accidents/incidents world-wide.
Biological Effects of Radiation
Exposure
 Ionising radiation affects the cells of the body
through damage to DNA by:
 Direct interaction with DNA, or
 Through ionisation of water molecules etc
producing free radicals which then damage the
DNA.
 Some damaged cells might be killed outright so do
not pass on any defect.
 In some cases cell repair mechanisms can correct
damage depending on dose.
Biological Effects of Radiation
Exposure
 Deterministic Effects.
 Threshold beneath which there is no effect and
above which severity increases with exposure.
 High dose effects - cells may be killed by damage
to DNA and cell structures.
 Clinically observable effects include:
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5 Sv to whole body in a short time is fatal.
60 Sv to skin causes irreversible burning.
5 Sv to scalp causes hair loss
4 Sv to skin causes brief reddening after three weeks
3 Sv is threshold for skin effects.
Biological Effects of Radiation
Exposure
 Stochastic (Chance) Effects
 No threshold dose, probability of effect
increases with dose but severity of effect
remains unchanged
 Lower dose effects
 No obvious injury,
 Some cells have incorrectly repaired the DNA
damage and carry mutations leading to
increased risk of cancer.
 Rapidly dividing cells most at risk – blood
forming cells in bone marrow; gut lining.
Cancer Risk at Low Doses
 Evaluation of Cancer
Risk
 Studied for decades.

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
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atomic bomb explosions in
Japan,
fallout from nuclear
weapons tests
radiation accidents.
medical irradiations,
work (e.g. nuclear power
industry)
living in a region that has
unusually high levels of
radioactive radon gas or
gamma radiation.
Main Area of Available Data for
Study
E
F
F
E
C
T
Main Area of Interest
for Radiation
Protection
RADIATION DOSE
Cancer Risk at Low Doses
 Life-time risk of cancer from all causes of about 20–
25%.
 Exposure to all sources of ionising radiation (natural
plus man-made) could be responsible for an
additional risk of fatal cancer of about 1%
 Dose from natural background radiation is about 2.2
mSv per year.
 Dose from non-medical, man-made radiation


0.02 to 0.03 mSv per year (1/100th natural background),
0.01% of additional cancer risk.
 More significant cancer risk factors include:



cigarette smoking,
excessive exposure to sunlight, and
poor diet.
Biological Effects
 4-10 Sv - death
 1 Sv - clinical effects
 100 mSv - clinical effects on foetus
 50 mSv - max lifetime univ. dose
 20 mSv - annual whole body dose limit
 6 mSv - classified worker
 2.5 mSv - average annual exposure (UK)
 1 mSv - foetus after pregnancy confirmed
 150 - 250 uSv - max annual dose at univ.
 20 uSv – average annual dose at univ.
Perspective on Exposures
 Nature of work AND precautions in place
show risk from exposure at work is extremely
low.
 10-15% of those subject to dosimetry receive
a measurable dose,
 Average dose ~ 18uSv


0.1% of the dose limit of 20 mSv,
1% of that received from natural background
radiation (2.2 mSv).
Follow Safe Procedures
Properties of Main Isotopes
Isotope
HalfLife
Radi
ation
Type
B
Energy
18.6 keV
Range in
Air
Dose
Rate at
10 cm
from
1 MBq**
Annual
Limit on
Intake*
Tritium
Water
(organic)
Carbon 14
12.4 y
6 mm
5730 y B
156 keV
24 cm
1 GBq
480 MBq
15 MBq
Sulphur 35
87.4 d
B
167 keV
26 cm
34 MBq
Phosphorus 25.6 d B
33
Phosphorus 14.3 d B
32
Iodine 125 60.1 d X
Y
250 keV
46 cm
14MBq
1.71 MeV
790 cm
1 mSvh-1
30 keV
35 keV
metres
14 uSvh-1 1 MBq
6 MBq
Legislation
 Health and Safety

Ionising Radiations Regulations 1999
 Environmental

Environmental Permitting Regulations 2010

(Supersede Radioactive Substances Act 1993)
Ionising Radiations Regulations
1999
 Worker protection
 dose limits
 Justification

Radiation Project Proposal Forms (Rad 1-3)
 risk assessment for exposure
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Risk Assessment Forms (Rad 5 or 6)
 restrict exposure through
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equipment, procedure, experimental design
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time,
shielding,
distance (inverse square law)
Protection through distance
 Inverse square law applies
Distance
1m
2m
4m
Dose rate
(uSv/hr)
1
0.25
0.06
Protection through distance
 HOWEVER !!!!!!
 Distance
 100cm
 50cm
 30cm
 10cm
 1cm
 1mm
Dose rate (uSv/hr)
1
4
9
100
10,000
1,000,000
Ionising Radiations Regulations 1999
 Local Rules
 RPS’s for all areas

Worker/Project registration
 Designation of areas
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access control
contamination monitoring
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Worker responsibility
Regular checks by RPS
 Secure storage and accounting
 Movement
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packaging and labelling
No posting or carriage on public transport
Environmental Permitting
Regulations 2010
 Enforced by Environment Agency.
 Licensing regime
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
stocks
accumulation and disposal of waste
specific limits on

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isotope and quantity,
disposal route and disposal period
 Strict record keeping essential

Isostock for Radiochemicals

Must be kept up to date
Administrative Controls
 Project Registration (Rad 1-3)
Isotopes
 Quantities
 Disposal routes
 Lab Facilities
 Worker Registration (Form)
 Project
 Dosemeter
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Look after it
Return at end of quarter – charges for late/lost badges
 Amend Details if Work Changes
The Use of Radiochemicals
in Life Science Research
Comparison of Common Isotopes
Safe Handling – 10 Golden Rules
Decomposition
Commonly used isotopes
Isotope
14
Emission






Energy
(Mev)
0.156
0.0186
0.035
1.709
0.249
0.167
Half Life
5730 years
12.35years
60 days
14.3 days
25.4 days
87.4 days
2000
Ci/mAtom
9000
Ci/mAtom
3500
Ci/mAtom
1500
Ci/mAtom
-
2710
300
40
C
3
H
29
Max. Spec. 62.4
mCi/mAtom Ci/mAtom
Activity
Mean path 42
length (mm)
0.47
125
I
32
P
33
P
35
S
38
Carbon-14
 Low energy  emission - no shielding required
 Long half-life - less time pressure
 Low specific activity - low sensitivity
 Detection




scintillation counter
autoradiography
Geiger counter
phosphorimager
 Labelled compounds generally stable - few
decomposition problems
39
H-3 (Tritium)
 Very low energy  emission - no shielding required
 Long half - life
 High specific activity - reasonably sensitive, but
weak emission
 Detected by
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
scintillation counter
autoradiography
fluorography
phosphorimager
detection less easy
less accurate and
less efficient than 14C
 Labelled compounds less stable - radiation
decomposition problems
40
Iodine -125
  emission - lead shielding required
 Short half-life - time pressures
 Very high specific activities - high sensitivities
 Detection




Gamma counter
Scintillation probe
Autoradiography
phosphorimager
 Labelled compounds stable - some decomposition
problems
41
Phosphorus - 32

High energy  emission - shielding required (perspex
and lead)

1 MBq in 1ml plastic vial @ 1m
@ 10cm

30MBq in 1ml plastic vial @ 10cm 6mSv/hr
25 hours of work = 150mSv,
i.e.Classified Worker

2.5uSv/hr
200uSv/hr
NEVER HOLD VIAL IN FINGERS
42
Phosphorus - 32
 High energy  emission - shielding required (perspex
and lead)
 Short half-life - time pressures
 Very high specific activity - very high sensitivity
 Detection





Scintillation counter
Cerenkov counter
Geiger counter
Autoradiography
phosphorimager
 Labelled compounds unstable - decomposition
problems
Phosphorus - 33
 Low energy  emission - low shielding required (1cm
perspex)
 Short half -life - time pressures
 High specific activity - high sensitivity
 Detection

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Scintillation counter
Proportional counter
Geiger counter
Autoradiography
phosphorimager
Easy to detect
and accurate counting
 Labelled compounds generally stable - few
decomposition problems
44
Sulphur -35
 Low energy  emission - low shielding required (1cm
perspex)
 Shortish half-life - some time pressures
 High specific activity - high sensitivity
 Detection





Scintillation counter
Proportional counter
Geiger counter
Autoradiography
phosphorimager
 Labelled compounds generally stable - few
decomposition problems
45
Resolution
Intensifying
screen
Plastic base
aasAS
Emulsion
Anti scratch
H-3
Image on film:
C-14/ S-35/ P-33
P-32/ I-125
Blank
46
Choosing an isotope
 Detection method
 Resolution required
 Sensitivity
 Specific activity
 Formulation - aqueous/ethanol
(stabilised/free radical scavenging)
 Position of label - important in metabolic
studies / can affect protein binding
47
Working safely with radioactivity
The Ten Golden Rules
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
Understand the nature of the hazard and get practical training
Plan ahead to minimise handling time
Distance yourself appropriately from sources of radiation
Use appropriate shielding
Contain radioactive materials in a defined work area
Wear appropriate protective clothing and dosimeters
Monitor the work area frequently
Follow the local rules and safe ways of working
Minimise accumulation of waste and dispose of it correctly
After completion of work monitor yourself and work area
48
Decomposition
 Chemical decomposition caused by, or
accelerated by:



the presence of one or more radioactive atoms in
the molecule
Free radicals
Micro-organisms
 Stock solutions and aliquots will decompose
over time and become unusable.
49
Modes of decomposition
Mode of
Cause
Method for control
decomposition
Primary (internal) Natural isotopic decay None for a given specific
activity
Primary
Direct interaction of
Dispersal of labelled
(external)
the radioactive
molecules
emission with
molecules of the
compound
Secondary
Interaction of the
Dispersal of labelled
excited species with
molecules, cooling to low
molecules of the
temperatures, add free
compound
radical scavenger
Chemical and
Thermodynamic
Cooling to low
microbiological
instability of the
temperatures, removal of
compound and poor
harmful agents
environment
50
Typical rates of decomposition
 Carbon -14
 Tritium
 Sulphur -35
 Phosphorus -32
 Iodine -125
1-3% per year
1-3% per month
1-3% per month
1-3% per week
5-10% per month
51
Stability of [2,4,6,7-³H]Oestradiol
Radiochemical purity
100%
90%
80%
4
8
12
15
Time (weeks)
20
52
Effect of Specific Activity
Decomposition of [-³²P]ATP at 20°C
100%
0.17
1.7
Radiochemical purity
90%
60%
Specific activities in Ci/mmol
17
30%
Time (days)
7
53
Effect of temperature
Stability of [35S]Methionine
100%
Radiochemical purity
-140º
-80º
90%
80%
-20º
70%
Time (weeks)
1
3
6
54
Effect of temperature
Stability of [³H]Uridine
100%
Radiochemical purity
+2º
90%
80%
-20º
70%
3
6
Time (weeks)
9
12
55
Effect of free radical scavengers
Decomposition of [U-14C]Phenylalanine at 20ºC
100%
+ 3% ethanol
Radiochemical purity
90%
Aqueous solution
80%
70%
Time (months)
1
2
3
4
56
Control of decomposition
 Store at lowest specific activity
 Store at lowest radioactive concentration
 Disperse solids - store under inert atmosphere
 Add 2% ethanol to aqueous solutions
 Store in the dark
 Use stabilised formulations
 Tritium - Store just above freezing point or -140
 Reanalyse immediately prior to use
 Aliquot if long storage expected
57
Contamination Control Video
END
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