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Safe Working With Ionising Radiation Programme What is

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Title: Safe Working With Ionising Radiation Programme What is


1
Safe Working With Ionising Radiation
2
Programme
  • What is radiation?
  • How is it measured?
  • Biological harm
  • Doses into perspective
  • Legislation
  • Unsealed work
  • Isotope selection
  • Safe working
  • Decomposition

3
Objectives
  • Foundation for Training in School
  • Understand principles
  • radiation types and effects
  • biological effects
  • relative risk
  • legislation
  • university arrangements
  • Safe Practice

4
Atomic Structure
5
Isotopes
  • Variable neutron number
  • Unstable nuclei transform
  • Ionising radiation emitted

6
Ionisation
  • Energy transfer
  • Enough energy 13 eV

7
Half - life
Isotope Half-Life Tritium 12.4 y Carbon
14 5730 y Sulphur 35 87.4 d Phosphorus 33 25.6
d Phosphorus 32 14.3 d Iodine 125 60.1 d
8
Types of Radiation
  • Video

9
Types of Radiation
  • Alpha
  • From heavy nuclei (e.g. Americium 241)
  • Helium nuclei (2P2N)
  • 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

10
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

11
Types of Radiation
  • Bremsstrahlung
  • 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.

12
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

13
Types of Radiation
  • X-Radiation
  • 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

14
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.

15
Units of Radiation
  • SI units Becquerel, Gray, Seivert
  • replaced Curies, Rems, Rads
  • Activity
  • Dose
  • absorbed
  • equivalent
  • committed

16
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
  • Stock, disposals
  • Expt protocols

17
Units of Radiation - dose
  • Absorbed - Gray (Gy)
  • Radiation energy deposited
  • 1 Gy 1 joule/kg
  • Dose Equivalent - Seivert (Sv)
  • modified for relative biological effectiveness
  • beta, gamma, X 1
  • alpha, neutrons 10-20

18
Units of Radiation - relationship
  • quantity x energy dose rate (uSv. hr-1)
  • number of DPS (Bq)
  • energy in electron volts
  • 1 eV 1.6 x 10-13 joules
  • e.g. 1 MBq of a 1MeV source, thus
  • 1 MeV 1.6 x 10-7 joules, and
  • 1 MBq 106 disintegrations per second, hence
  • Energy flux 1.6 x 10-1 joules/second
  • 576 joules/hour
  • Note 1 Sv/h 1 joule/kg/h deposited in tissue

19
Units of Radiation - committed
  • Internal
  • irradiation until decay or elimination
  • radiological and biological half-lives
  • data for 50-year effect
  • Annual Limit on Intake (ALI)
  • limit on committed dose equivalent
  • quantity causing dose limit exposure

20
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.

21
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.

22
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
  • 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.

23
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.

24
Cancer Risk at Low Doses
  • Evaluation of Cancer Risk
  • Studied for decades.
  • 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.

25
Cancer Risk at Low Doses
  • Life-time risk of cancer from all causes of about
    2025.
  • 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.

26
Cancer Risk at Low Doses
  • Most simplistic assumption is linear relationship
    between dose and risk
  • This produced the following risk probabilities
  • Fatal Cancer 1 in 25,000 per mSv
  • Non-fatal cancer 1 in 125,000 per mSv
  • Hereditary Effect 1 in 125,000 per mSv
  • Combined risk 1 in 18,000 per mSv

27
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.

28
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

29
Properties of Main Isotopes
30
Legislation
  • Health and Safety
  • Ionising Radiations Regulations 1999
  • Environmental
  • Radioactive Substances Act 1993

31
Ionising Radiations Regulations 1999
  • Worker protection
  • dose limits
  • justification
  • risk assessment for exposure
  • restrict exposure through
  • equipment, procedure, expt design
  • time, distance , shielding

32
Protection through distance
  • Inverse square law applies
  • Distance Dose rate (uSv/hr)
  • 1m 1
  • 2m 0.25
  • 4m 0.06

33
Protection through distance
  • HOWEVER !!!!!!
  • Distance Dose rate (uSv/hr)
  • 100cm 1
  • 50cm 4
  • 30cm 9
  • 10cm 100
  • 1cm 10,000
  • 1mm 1,000,000

34
Ionising Radiations Regulations 1999
  • Local Rules
  • RPSs for all areas
  • Worker/Project registration
  • Designation of areas access control
  • Secure storage and accounting
  • Movement
  • packaging and labelling
  • No posting or carriage on public transport

35
Radioactive Substances Act 1993
  • Enforced by Environment Agency.
  • Licensing regime
  • stocks
  • accumulation and disposal of waste
  • specific limits on
  • isotope and quantity,
  • disposal route and disposal period
  • Strict record keeping essential

36
Administrative Controls
  • Project Registration
  • Isotopes
  • Quantities
  • Disposal routes
  • Lab Facilities
  • Worker Registration
  • Project
  • Dosemeter - Care
  • Amend Details if Work Changes

37
End of Part One
  • X-ray and Sealed Source Users to Other Room
  • Harry Zuranski
  • Sign in.

38
Isostock - Computer Recordshttp//www.nottingham.
ac.uk/safety/publications/radiation.html
39
The Use of Radiochemicals in Life Science Research
Safe handling and choice of Isotope
Slide Set Provided by Amersham Biosciences
A
40
Definitions
  • Radioactivity - the property of certain nuclides
    of emitting radiation by the spontaneous
    transformation of their nuclei
  • Specific activity - Activity per unit mass of a
    compound
  • Radioactive concentration - The activity per unit
    quantity of any material in which a radionuclide
    occurs
  • Radiochemical purity - the amount of
    radioactivity in the stated chemical form ( does
    not take into account non-radioactive impurities)

41
Production of radiochemicalsneutron in / proton
out
42
Isotope production
  • Isotope
  • 3 Hydrogen (Tritium)
  • 14 Carbon
  • 35 Sulphur
  • 32 Phosphorus
  • 33 Phosphorus
  • 125 Iodine
  • Stable daughter nuclide
  • Helium -3
  • Nitrogen -14
  • Chlorine - 35
  • Sulphur -32
  • Sulphur - 33
  • Tellurium - 125

43
Commonly used isotopes
44
14C maximum specific activity
45
Commonly used isotopes
46
Carbon-14
  • Low energy b 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
  • Label is part of the backbone of molecule
  • Labelled molecules are natural species - no
    artefacts

47
14C is in the backbone
48
Carbon-14
  • Low energy b 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
  • Label is part of the backbone of molecule
  • Labelled molecules are natural species - no
    artefacts

49
H-3 (Tritium)
  • Very low energy b emission - no shielding
    required
  • Long half - life
  • High specific activity - reasonably sensitive,
    but weak emission
  • Detected by
  • scintillation counter detection less easy
  • autoradiography less accurate and
  • fluorography less efficient than 14C
  • phosphorimager
  • Labelled compounds less stable - radiation
    decomposition problems
  • Label on periphery of molecule - no confidence in
    label position
  • Labelled molecules are natural species - no
    artefacts

50
Label moves around the molecule
51
H-3 (Tritium)
  • Very low energy b emission - no shielding
    required
  • Long half - life
  • High specific activity - reasonably sensitive,
    but weak emission
  • Detected by
  • scintillation counter detection less easy
  • autoradiography less accurate and
  • fluorography less efficient than 14C
  • phosphorimager
  • Labelled compounds less stable - radiation
    decomposition problems
  • Label on periphery of molecule - no confidence in
    label position
  • Labelled molecules are natural species - no
    artefacts

52
Iodine -125
  • g 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
  • Label covalently bound to molecules - position of
    label fixed
  • Not often part of natural molecule - artefacts

53
Phosphorus - 32
  • High energy b emission - shielding required
    (perspex and lead)
  • 1 MBq in 1ml plastic vial _at_ 1m 2.5uSv/hr
  • _at_ 10cm 200uSv/hr
  • 30MBq in 1ml plastic vial _at_ 10cm 6mSv/hr
  • 25 hours of work 150mSv, i.e.Classified
    Worker
  • NEVER HOLD VIAL IN FINGERS

54
Phosphorus - 32
  • High energy b 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
  • Label covalently bound to molecule - position
    fixed
  • Labelled molecules natural species - no artefacts

55
Phosphorus - 33
  • Low energy b emission - low shielding required
    (1cm perspex)
  • Short half -life - time pressures
  • High specific activity - high sensitivity
  • Detection
  • Scintillation counter Easy to detect
  • Proportional counter and accurate counting
  • Geiger counter
  • Autoradiography
  • phosphorimager
  • Labelled compounds generally stable - few
    decomposition problems
  • Label covalently bound to molecule - position of
    label fixed
  • Labelled molecules are natural species - no
    artefacts

56
Sulphur -35
  • Low energy b 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
  • Label covalently bound to molecule - position of
    label fixed
  • Labelled molecules may be natural (S-35 Met) or
    not (S-35 nucs)

57

Deoxynucleotide triphosphate structure
g b a
Base
O
OCH
P
P
P
2
H
H
OH
H
58
Resolution
Intensifying screen
Plastic base
aasAS
Emulsion
Anti scratch
H-3 C-14/ S-35/ P-33 P-32/ I-125
Image on film Blank
59
Comparison P-32/P-33/S-35
  • Resolution in autoradiography
  • S-35 gt P-33 gt P-32
  • Sensitivity in detection
  • P-32 gt P-33 gt S-35
  • Probe stability
  • S-35 gt P-33 gt P-32
  • Decay rate
  • P-32 gt P-33 gt S-35

60
Choosing an isotope
  • Detection method
  • Resolution required
  • Sensitivity
  • Specific activity
  • Formulation - aqueous/ethanol
  • Position of label - important in metabolic
    studies / can affect protein binding

61
Working safely with radioactivity
The Ten Golden Rules
  • 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

62
Radiation Decomposition
  • The chemical decomposition of a compound caused
    by, or accelerated by, the presence of one or
    more radioactive atoms in the molecule

63
Modes of decomposition
64
Typical rates of decomposition
  • Carbon -14 1-3 per year
  • Tritium 1-3 per month
  • Sulphur -35 1-3 per month
  • Phosphorus -32 1-3 per week
  • Iodine -125 5-10 per month

65
Stability of 2,4,6,7-³HOestradiol
100
Radiochemical purity
90
80
4
8
12
20
15
Time (weeks)
66
Effect of Specific Activity
Decomposition of g-³²PATP at 20C
100
0.17
1.7
90
Radiochemical purity
60
Specific activities in Ci/mmol
17
30
7
Time (days)
67
Effect of temperature
Stability of 35SMethionine
100
-140º
-80º
90
Radiochemical purity
80
-20º
70
Time (weeks)
6
1
3
68
Effect of temperature
Stability of 35SCysteine
100
-140º
-80º
90
Radiochemical purity
60
30
-20º
1
5
3
2
4
Time (weeks)
69
Effect of temperature
Stability of ³HUridine
100

90
Radiochemical purity
80
-20º
70
12
6
3
9
Time (weeks)
70
Effect of slow freezing
Slow freezing concentrates the solute
71
Effect of free radical scavengers
Decomposition of U-14CPhenylalanine at 20ºC
100
3 ethanol
90
Aqueous solution
Radiochemical purity
80
70
Time (months)
4
2
3
1
72
Effect of free radical scavengers
Stability of 35SMethionine
100
90
50
Radiochemical purity
Control (SJ204)
Stabilised 35Smethionine (SJ1515)
0
30
20
10
Time (days)
73
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 RedivueTM formulations
  • Tritium - Store just above freezing point or -140
  • Reanalyse immediately prior to use
  • Aliquot if long storage expected

74
END
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