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Radiation Safety Course

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Radiation Safety Course Dr Salim Siddiqui Radiation Safety Officer Room 301.212A Tel: 9266 7193 Curtin University of Technology * S.Siddiqui-Radiation Safety Notes – PowerPoint PPT presentation

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Title: Radiation Safety Course


1
Radiation Safety Course
Dr Salim Siddiqui Radiation Safety Officer Room
301.212A Tel 9266 7193 Curtin University of
Technology
2
  • Learning Objectives
  • On completion of this course, you should be able
    to demonstrate the knowledge of
  • 1. Sources of Radiation (Man-made and Natural)
  • 2. Types of Radiation (Ionizing and Non Ionizing
    Radiation)
  • 3. General Characteristics of Radiation
  • 4. Radioactivity
  • 5. Quantification of Radiation (Units)
  • 6. Radiation Exposure Measurement
  • 7. ICRP Recommendations for Dose Limits
    (Permissible Dose)
  • 8. Radiation Hazards (External and Internal)
  • 9. Biological Effects of Radiation
    (Deterministic and Stochastic)
  • 10. International Commission on Radiological
    Protection.
  • 11. Radiation Safety Act and Regulations
  • 12. Role of RSO
  • 13. Role of EduSafe

3
1. Sources of Radiation
  • Man-made sources x-rays, radioisotopes.
  • Used in various industries, eg. Radiography,
    radiotherapy, nuclear medicine, mining etc.
  • (b) Natural sources
  • (i) External cosmic and terrestrial, uranium,
    thorium in soil, water.
  • (ii) Internal Radionuclide within our body, e.g.
    C-14, K-40 and also other radionuclides that are
    ingested and inhaled.
  • e.g. 222Rn gas.

4
2. Types of Radiation
(a) Ionizing Radiation Radiation having
sufficient energy to cause ionization in matter.
e.g. x-rays, gamma rays, charged particles
neutrons. (NHMRC p r-34) (b) Non-ionizing
Radiation Visible light, UV radiation,
microwaves, laser, Infrared, Ultrasound
5
3. General Characteristics of Radiations
  • Particulate Radiation Sub-atomic particles with
    mass and charge. e.g. alpha, beta, protons,
    electrons, neutrons
  • EM Radiation Electromagnetic waves with no mass
    and charge. e. g. X-rays, gamma rays.

6
Characteristics of Radiations
  • Alpha particles
  • Generally emitted by heavy radioisotopes
  • It is a helium nucleus with two protons and two
    neutrons in the nucleus.
  • Typical energy range (4 8 MeV)
  • Low range (lt10 cm in air, 60 µm in tissue)
  • Can be stopped by a sheet of paper

Example
7
  • Beta particles
  • There are two types of beta decay
  • 1. Negative beta decay
  • In this process a neutron in the nucleus
    transforms into a proton resulting in the
    emission of an electron and an anti-neutrino.
  • 2. Positive beta decay
  • In this process a proton in the nucleus
    transforms into a neutron resulting in the
    emission of a positron and a neutrino.
  • Typical energy range is several keV to few MeV.
    Unlike alpha particle beta particle has
    continuous energy range.
  • Low range (a few mm in tissue)

8
Example of negative beta decay
Example of positive beta decay
9
  • Gamma rays
  • -are electromagnet waves, that travel with the
    speed of light in vacuum (roughly air).
  • -have no charge
  • - are emitted from the excited nucleus following
    alpha or beta decay as tiny packets of energy
    called photons.
  • There are very few isotopes that are pure beta
    emitters and do not emit gamma rays.
  • e.g. H-3, C-14, P-32

10
  • X-rays
  • are electromagnetic waves, that travel with the
    speed of light in vacuum (roughly air).
  • have no charge
  • x-rays are generated when fast moving electrons
    are decelerated in a high Z target. The emitted
    spectrum is continuous in energy (Bremsstrahlung
    spectrum).
  • characteristic x-rays are produced when an
    excited orbital electron drops back to a lower
    energy orbit. The difference between the two
    energy levels is emitted as an x-ray photon which
    appears as a line spectrum
  • x-rays are used in medical, research and other
    industries

11
  • Neutrons
  • These are neutral particles with no charge
  • There are no naturally occurring nuclei which
    emit neutrons ( Except Californium-252)
  • Neutron sources used in industry and research are
    produced through nuclear reactions.
  • Emitted neutrons are not mono-energetic
  • Typically, En 0.1 13 MeV

12
In general neutrons are produced by three main
methods as follows i) Nuclear reaction induced
by alpha or gamma emitting isotopes ii) Nuclear
reaction induced by charged particles from
accelerator iii) Research reactors
Example Ra - Be neutron source or Am-Be neutron
source
13
Penetrating abilities of various radiation
Quiz Which of these radiation can cause internal
and external hazard?
Ans.
14
4. Radioactivity
Spontaneous emission of radiation from unstable
nuclei
Radioactive decay law If N is the number of
nuclei present and ?N decay in time ? t, we find
that
15
Half-LifeTime taken for half the radioactive
nuclei to decay. It varies, according to the
isotope, from less than a few micro seconds to
more than a billion years.
16
5. Quantification of Radiation (Units)
Activity Determines the strength of a
radioactive source. The number of disintegration
occurring per unit of time is called the
activity.
Curie it is the activity of that quantity of
radioactive material in which 3.7?1010 atoms are
disintegrating per second.
Old unit 1 Curie 3.7x1010 dps SI unit 1 Bq
1 dps
Quiz. Which source has a higher activity, 1 gram
of 238U or 1 gram of 234Th?
17
Exposure measure of the amount of ionization
produced in air by x or gamma radiation.
Old unit 1 R 2.58 x 10-4 C/kg SI unit 1 X
unit 1 C/kg Conversion 1 X unit 3881 R
Roentgen Amount of x or gamma radiation that
will liberate a charge of 2.58 ?10-4 C in I kg of
dry air at STP.
Q. But how much energy is absorbed in matter?
18
Radiation Absorbed Dose (rad) Energy deposited
by any type of radiation in any material (air,
water, biological tissue etc) per unit mass.
Old unit 1 rad 10 mJ/kg SI unit 1 Gy 1
J/kg Conversion 1 Gy 100 rad
19
Quiz. Which will deposit more energy in tissue,
1 rad of x-rays or 1 rad of ??
Ans. Since ? particles travel slower than x or ?
of the same energy. Therefore, it can produce
more ionization within a small volume of the
tissue, thus depositing more energy.
20
Quiz. Which will cause more damage to tissue?
Ans. Since alpha particle deposits more energy,
hence can cause more damage. So the chance of
damage to tissue depends not only on the absorbed
dose, but also on the i) type and energy of
radiation. ii) type of irradiated tissue
21
The modified unit taking into account the type
and energy of radiation is called the
Equivalent Dose Equivalent Dose Absorbed Dose
? wR Unit of equivalent dose is Sievert. (R.
Sievert, Swedish radiologist)
 
Some values of wR are given in the following
table
22
However different tissues show different
radiological sensitivities as shown in the table
on next page
The modified unit taking into account the
radiological sensitivities of radiation is called
the Effective Dose
Effective Dose Equivalent Dose ? wT SI unit
Sievert Old unit rem
Effective Dose Absorbed Dose ? wR ? wT
23
Tissue or organ Tissue weighting factor
Gonads 0.20
Bone marrow (red) 0.12
Colon 0.12
Lung 0.12
Stomach 0.12
Bladder 0.05
Breast 0.05
Liver 0.05
Oesophagus 0.05
Thyroid 0.05
Skin 0.01
Bone surface 0.01
Remainder 0.05
Total 1.00
24
This unit of Effective dose is used only in
radiation protection. Personal monitoring devices
such as film badge are designed to record dose in
Sievert.
Quiz. Which will cause more damage to tissue 1
rem of x-rays or 1 rem of ? ?
Ans.
25
Summary Quantities and Units of Radiation
Quantity Measure of Traditional Unit SI Unit
Activity Decay rate Curie Bq
Exposure Ionization in air Roentgen C/kg
Absorbed dose Energy absorption rad Gray
Effective Dose Biological effectiveness rem Sv
26
Summary Activity 1 Curie 3.7x1010 dps 1 Bq
1 dps Exposure 1 R 2.58 x 10-4 C/kg 1 X
unit 1 C/kg 1 X unit 3881 R Absorbed
dose 1 rad 10 mJ/kg 1 Gy 1 J/kg 1
Gy 100 rad Equivalent Dose Sievert Gray ?
wR 1 Sv 100 rem Effective Dose Sievert
Gray ? wR ? wT
27
6. Radiation Exposure Measurement
  • The standard detector is an ionization chamber
  • The current trough a resistor is a measure of
    exposure C/kg/s Gy/s
  • Personal Monitoring
  • - Film badges
  • - TLD (Thermo-luminescent dosimeter) (LiF Mg,
    Ti)
  • - OSL (Optically stimulated luminescence)
    (Al2O3 C)
  • - Curtin uses Luxel dosimeter (Sensitivity 0.01
    mSv)

28
Personal Radiation Monitoring
  • Badges are issued by the RSO upon request
  • Badges are issued and collected quarterly
  • Badges are to be worn all the time when working
    with radiation
  • Badges should not be tempered or misused (Safety
    Regulation)
  • Inform your supervisor of any spills or unusual
    exposure to radiation

29
7. ICRP Recommendations for Dose Limits
The Effective Dose limits are as follows
  • Occupational exposures 20 mSv/year
  • (averaged over 5 consecutive years, and should
    not exceed 50 mSv in any single year)
  • General public 1 mSv/year (averaged over 5
    years)
  • Pregnancy 1 mSv/y to the abdominal surface

Note These limits do not include, Natural
background and Medical diagnosis and therapy dose
30
Equivalent Dose Limits
  • The eye lens150 mSv/y
  • The skin 500 mSv/y (over any 1 cm2 of skin)
  • The hands and feet 500 mSv/y

Note For general public, the limits are 1/10th
of the above values.
31
8. Radiation Hazard
  • Two types of radiation hazard are involved when
    working with radioactive materials
  • External radiation hazard
  • Internal contamination hazard

(i) External Hazard Associated with high
activity sources that emit x, ?, neutron and high
energy ?. These radiations can penetrate the body
and result in a high absorbed dose.
32
STDA Rule to Reduce the External Hazard
  • SHIELDING Keep suitable shielding between user
    and source
  • eg. use Pb, concrete Al, perspex
    shielding
  •  
  • TIME Minimize handling time
  • Dose Dose rate x Time
  •  
  • DISTANCE Maximize the distance between user and
    Source.
  • Dose rate ? 1/r2
  •  
  • ACTIVITY Minimize activity of the source.
  • Doe rate ? Activity

33
In case of accident
  • don't touch any material
  • cordon off the area and place warning signs
  • stay at a safe distance from the accident site
  • don't leave the site unless you are checked of
    contamination
  • don't eat drink or smoke at the accident site
  • call the Radiation safety supervisor of your area
    or Radiation safety officer

34
ii) Internal HazardsRadionuclides emitting ?, ?
taken internally into the human body can deposit
their energy in the host tissue, thus causing
damage.
The routes of entry into the body may be
  • Ingestion
  • from surface contamination. Eating drinking in
    workplace
  • Inhalation
  • from contaminated air, due to airborne dust,
    vapours
  • Absorption
  • either directly through the skin or through cuts
    and wounds

35
9. Biological Effects
  • When radiation traverses through the tissue,
    following may happen
  • (i) no damage to the cells
  • (ii) cell is damaged, but is repaired
  • (iii) cell survives but with permanent damage.
  • This is called mutation. Such cells multiply
    with deformity and are thought to eventuate in
    cancer.
  • (iv) cell is totally damaged.
  • (death of many cells causes Radiation sickness)

36
Categories of Biological Effects
37
Categories of Biological Effects
Biological effects may be divided into two
categories (i) Stochastic (ii) Deterministic
(i) Stochastic effects Stochastic means chance
or random effect in an exposed person. "An effect
known to occur sometimes as a consequence to
radiation, but which may or may not be expressed
in a particular exposed person" (NHMRC, 1995, p
r-36)
38
The probability of the effect is proportional to
the dose, with out any dose threshold. This
occur when the cell that has been irradiated is
modified rather than killed. This may lead to
cancer in the exposed person, or mutation in the
off springs.
39
The stochastic effects are further classified
as  Somatic When the effects appear in the
exposed person. eg. cancer Genetic When effects
appear in the off springs of the exposed person,
eg. mutation. This happens if the damage is
incurred to the reproductive cells of the exposed
person.
40
(ii) Deterministic effects Which can cause "
partial loss of function of an organ or tissue
(NHMRC, 1995, pr-32) These are caused when the
dose is above the threshold value. The severity
of the effect varies with the dose. Some of the
examples are, radiation sickness, cataracts, and
skin damage
41
10. International Commission on Radiological
Protection (ICRP)
  • ICRP was formed in 1928. It is a fully
    independent body, free of governments or nuclear
    industry constraints.
  • The function of the ICRP is
  • (ii) set dose limits for radiation workers.
  • these limits are set to prevent the occurrence
    of deterministic effects by keeping doses below
    the thresholds for individual tissue and also to
    reduce the incidence of stochastic effects, to an
    acceptable level. (iii) set dose limits for
    general public.

42
Principles of Radiological Protection ICRP 1977
  • Justification of a practice No practice
    involving exposures to radiation should be
    adopted unless it produces sufficient benefit to
    the exposed individuals or to society to offset
    the radiation detriment it causes.
  • (ii) Optimization of protection In relation to
    any particular source within a practice, the
    magnitude of individual doses, the number of
    people exposed, and the likelihood of incurring
    exposures where these are not certain to be
    received should all be kept as low as reasonably
    achievable (ALARA Principle) economic and social
    factors being taken into account.
  • (iii) Dose limits The exposures of individuals
    from the combination of all the relevant
    practices should be subject to dose limits, or to
    some control of risk in the case of potential
    exposures.
  • (ICRP Guidelines, 1991, from NHMRC 1995,
    p r-7)

43
National Health Medical Research Council, NHMRC
  • NHMRC was formed in 1936
  • The council is responsible for setting
    radiological protection standards in
    occupational, medical and public, in Australia.
  • NHMRC takes the recommendations of the ICRP as
    the basis for its own recommendations and then "
    implement legislation directed towards the
    effective control of exposure of people to
    radiation" (NHMRC, 1995, p r-v).

44
Radiological Council of WA
  • The Radiological Council of WA is appointed under
    the Radiation Safety Act 1975. It is a statutory
    body responsible for the administration of the
    Radiation Safety Act through the Radiation Health
    Section of the Health Department of WA.
  • Its function is
  • (i) advising the minister for health on hazards
    of radiation
  • (ii) implementing and enforcing the Act
  • (iii) inducting inquiry into alleged
    contravention
  • (iv) suspending or cancelling licence and
    registration
  • (v) investigating and prosecuting offences under
    the act.

45
11. Radiation Safety Act (1975) and Radiation
Safety (General) Regulations (1983)
  • Under the States Radiation Safety Act, all
    premises holding x-ray equipment, radioactive
    substances (including radiation gauges) and
    prescribed electronic products ( including lasers
    and ultraviolet transilluminators) are registered
    with the Radiological Council of WA.
  • The registrant of the premises is responsible for
    the safe use of radioactive substances and the
    radiation generating equipments, and the safety
    of the users and the public as described in the
    Radiation Safety (General) Regulations (1983)

46
Radiation Safety Regulation
  1. All premises involved with the radiation work are
    registered.
  2. All radioactive substances, x-ray equipment and
    prescribed electronic products are registered.
  3. All personnel involved in radiation work hold a
    valid personal radiation licence, or work under
    the supervision of a person holding a valid
    radiation licence
  4. All personnel involved in radiation work are
    registered with the Radiation Safety Office.
  5. All personnel involved in radiation work must
    wear personal radiation monitoring device.

47
  • 6. All Radiation monitoring equipment used in
    work place are maintained and regularly
    calibrated.
  • 7. Any acquisition or use of radioactive
    materials must be reported to Radiation Safety
    Office.
  • 8. Any project involving use of radiation or
    radioactive materials must obtain clearance from
    the Radiation Safety Office.

Safety Rules for All When dealing with radiation
work, each person is responsible for his/her own
safety and also for the safety of people around.
48
12. Role of the RSO
  • Ensures site, equipment and personnel are
    licensed as required by the RC.
  • Vetting students projects involving radiation
  • Ensure students are supervised by a licencee
  • Project details (candidacy) must be submitted to
    the RSO for approval.
  • Issue radiation approval number.
  • Issue radiation badges
  • Advise students to undergo radiation safety
    training. e.g. UWA unsealed course.

49
13. Role of EduSafe
  • EduSafe is a specialist area within Curtin which
    provides professional advice and services in OSH,
    Workers Compensation, and Injury Management. It
    has overarching responsibility for OSH matters
    within Curtin and maintains an informative
    website which includes a section on Radiation
    Safety.
  • Compliance with Radiation Safety requirements is
    overseen by a Radiation Safety Officer (RSO), and
    Radiation Safety Supervisors have been appointed
    in the main departments or locations that use
    radioactive materials or devices that generate
    radiation.
  • Projects are approved by the RSO through EduSafe.
  • Incidents are reported to EduSafe on-line.

End of Lecture
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