This document provides a summary of key principles of radiation protection from a lecture on the topic. It discusses the need for radiation protection given the risks of ionizing radiation exposure. It describes sources of background radiation including cosmic rays, terrestrial radiation, radionuclides in the body, and radon gas. It covers principles of radiation protection including justification, optimization, dose limits, and ALARA. It discusses dose limits for occupational, public, and medical exposures. The aims are to eliminate deterministic effects and reduce stochastic effects.

1. Radiation Protection Course For Radiologists
Lecture 5 of 8
Principles of Radiation Protection
Prof Amin E AAmin
Dean of the Higher Institute of Optics Technology
&
Prof of Medical Physics
Radiation Oncology Department
Faculty of Medicine, Ain Shams University

2. Introduction
• Over half of all important decisions for the welfare of patients
are based on radiological procedures.

3. The Need For Radiation Protection
• The need for radiation protection exists because
exposure to ionizing radiation can result in deleterious
effects that manifest themselves not only in the exposed
individual but in his descendants as well.

4. Background Radiation
• Background radiation is a measure of the level of
ionizing radiation present in the environment at a particular
location which is not due to deliberate introduction
of radiation sources.
• Background radiation originates from a variety of sources,
both natural and artificial.

5. Sources Of Background Radiation
❖Natural sources of radiation
❖Artificial sources of radiation

6. Natural Sources Of Background
Radiation
❖Cosmic rays
❖Terrestrial radiation
❖Radionuclides in the body
❖Radon gas and its decay products

7. The Cosmic Ray
• Cosmic rays are high-energy protons and atomic nuclei which
move through space at nearly the speed of light.
• They originate from the sun, from outside of the solar system,
and from distant galaxies.
• They were discovered by Victor Hess in 1912 in balloon
experiments.

8. ❖ The cosmic ray
contribution to the
background radiation
varies markedly with
altitude.
❖ Note, that at cruising
altitude in a Boeing
747 the dose rate is
approximately 5
mSv/h
The Cosmic Ray

9. The Cosmic Ray

10. Let’s Compare Backgrounds
• Sea level - 30 mrem/year
from cosmic radiation
• 10,000 ft. altitude - 140
mrem/year
from cosmic radiation

11. Terrestrial Radiation
▪Terrestrial radiation comes from radioactivity emitting
from Primordial radio nuclides - these are radio nuclides
left over from when the earth was created.
▪Common radionuclides created during formation of earth:
–Radioactive Potassium (K-40) found in bananas,
throughout the human body, in plant fertilizer and
anywhere else stable potassium exists.
–Radioactive Rubidium (Rb-87) is found in brazil nuts
among other things.

12. Terrestrial Radiation
• Greatest contributor is 226Ra (Radium) with
significant levels also from 238U, 232Th, and 40K.
– Igneous rock contains the highest concentration
followed by sedimentary, sandstone and limestone.
– Fly ash from coal burning plants contains more
radiation than that of nuclear or oil-fired plants.

 ++

13. Radionuclides In The Body
• All element existing in the are mixture of different isotopes.
• Some of these isotopes are radioactive.
• The most important natural radionuclides that are found in the human body
are 238 U, 234 U, 232 Th, 210 Po, 210 Pb, 40 K, 226 Ra, 228 Ra, 14 C, 7 Be, 22 Na, and
the last three being cosmogenic in nature.
• In addition to these natural and cosmogenic types, the artificial radionuclides
such as 137 Cs and 90 Sr and many others can also be found in an extremely
small level.
• The concentration of the gamma emitting radionuclides, except for 40 K, in
human is so small that none of them can be detected using normal whole
body counters available to measure any intakes of radionuclides by
occupational workers.

14. Radon Gas And Its Decay Products
• Radon is a radioactive gas.
• It is colorless, odorless, tasteless, and chemically inert.
• Unless you test for it, there is no way of telling how much is
present.
• Radon is formed by the natural radioactive decay of uranium in
rock, soil, and water.
• When radon undergoes radioactive decay, it emits ionizing
radiation in the form of alpha particles.
• It also produces short-lived decay products, often called
progeny or daughters, some of which are also radioactive.

15. Artificial Sources Of Radiation Background
❖ Two artificial sources of radiation to which
every body is exposed;
❖ Fall-out from nuclear explosions.
❖ Radioactive waste, including discharges
from nuclear establishments.
❖ Another two artificial sources of radiation
to which not every body may be exposed;
❖ Medical Sources
❖ Consumer products

16. Relative Contribution Of Different
Sources Of Background Radiation
Body
17%
Cosmic
Rays
14%
Medical
12%
Artificial
1%
Radon
32%
Terestri
al
19%
Thoron
5%
Average radiation exposure from all sources: 2.8 mSv/year

17. Another Look at Sources

18. Annual Dose to the General Population
From Natural and Man-made Sources
Radiation Source
Effective Dose
Equivalent
(mrem/year)
Percentage of Total
Natural
Cosmic
Cosmogenic
Terrestrial
Inhaled (due to radon)
In the Body
Subtotal
27
1
28
200
39
295
8%
-
8%
55%
11%
82%
Man-made
Medical X-rays
Nuclear Medicine
Consumer Products
Others
Subtotal
39
14
10
<1
64
11%
4%
3%
-
18%
Rounded Total 360 100%

19. The Aim Of Radiological
Protection
The primary aim of radiological protection is
to provide an appropriate standard of
protection for man without unduly limiting the
beneficial practices giving rise to radiation
exposure.

20. Aims Of Radiation Protection
• Deterministic effects
❖RP aims to ELIMINATE them.
• Stochastic effects
❖RP aims to REDUCE them.

21. Practices Vs Intervention
Human activities which increases the overall
exposure to radiation are called practices. Other
human activities which can decrease the overall
exposure by influencing the existing causes of
exposure are called intervention.

22. System of radiation protection
“System of RP” is the name given by the ICRP
to the application of the 3 basic principles of RP
(no part should be taken in isolation):
❖ Justification
❖ Optimization
❖ Limitation

23. Principles of Protection in
Practices
❖Justification of a practise - no practice should be adopted
unless it produces sufficient benefit to the exposed individuals or
to society to offset the radiation detriment it causes.
❖Optimization of protection - the magnitude of individual
doses, the number of people exposed, and the likelihood of
incurring exposures should be kept as low as reasonably
achievable, economic and social factors being taken into account.
❖Individual dose limits - exposure should be restricted so, that
exposure of any individual from authorized source does not
exceed any relevant dose limit.

24. Principles of Protection in Intervention
• Justification - Intervention should do more good than harm.
Reduction in detriment resulting from the reduction in dose
should be sufficient to justify the harm and the costs (including
social cost), of the intervention.
• Optimization - the form, scale and duration of the
intervention should be optimized so as to produce the
maximum net benefit, under the prevailing social and
economic circumstances.
• Intervention is not normally likely to be necessary unless the
relevant intervention or action levels are exceeded

25. The Framework Of Radiation
Protection I
In diagnostic radiology the radiation sources (X-rays) are
deliberately used and are under control. Such situations are
called by the International Commission on radiation Protection
(ICRP) “practices”.
The basic components of the system of protection for “practices”
can be summarized as follows:
No practice involving exposures to radiation should be
adopted unless it produces at least sufficient benefit to the
exposed individuals or to society to offset the radiation
detriment it causes (this is called “justification of a practice”).

26. The Framework Of Radiation
Protection II
In relation to any particular source of radiation within a practice (e.g.
X-rays in radiodiagnostic), all reasonable steps should be taken to
adjust the protection so as to maximize the net benefit, economic and
social factors being taken into account (this is called “optimization of
protection”).
A limit should be applied to the dose (other than from medical
exposures) received by any individual as the result of all practices to
which he is exposed (this is called “application of individual dose
limits”).

27. Justification
❖ Justification means that any dose exposure
MUST have a benefit to exposed individuals
or to society.
❖ Thus, if the exposure has no benefit it is not
justified.
❖ i.e. Benefit of the radiation exposure must
outweigh the risk of exposure
Vs

28. Justification
• Justification of exposures is primarily the
responsibility of the medical professional i.e.
the Radiologist.
• The expected clinical benefit associated with
each type of procedure should have been
demonstrated to be sufficient to offset the
radiation detriment.

29. Optimization
❖Optimization means that minimum risk and
maximum benefits should be achieved,
economic and social factors being taken
into account.
❖Optimization includes the ALARA
criterion: doses should be “As Low As
Reasonably Achievable”, economic and
social factors being taken into account”
BENEFIT
RISK

30. ALARA Principle
❖ Radiation exposure of personnel and the general public
should be kept
As
Low
As
Reasonably
Achievable
❖ The ALARA Principle .
❖ With economic and social factors taken into account

31. ➢ correct exposure factors
➢ correct radiographic technique
➢ appropriate radiation protection
➢ appropriate development/viewing techniques
➢ appropriate radiographic positions for examination
➢ minimize repeat examinations
➢ continuing education
ALARA Policy

32. Optimisation
• For every exposure, operators must
ensure that doses arising from the
exposure are kept as low as reasonably
practicable and consistent with the
intended diagnostic purpose.
• This is optimisation.
• ALARA princible refers to the
continual application of the
optimization principle in the day-to-day
practice.

33. Optimization a Protection
LEVEL OF
INDIVIDUAL
RISK
UNACCEPTABLE RISK
LIMIT
TOLERABLE RISK
ACCEPTABLE RISK
DOSE (RISK)
CONSTRAINT

34. Optimisation – Staff Dose Investigation
Level (DIL)
• Once you start work with ionising radiation, you are
subject to legal dose limits – 6 mSv per year for non-
classified workers
• However, we have to define a Dose Investigation
Level
– 1.2 mSv per year
– Or 0.1 mSv per month
• This is a level of dose that should trigger an
investigation in conjunction with your RPA, and
ensures that you do not receive anywhere close to the
legal limit.

35. Limitation
❖ Doses should not exceed specific values, called
“individual dose limits”.
❖ These dose limits are established in order to
keep away from the “maximum risk level” so
that no individual is exposed to a radiation risk
that is judged to be unacceptable in any normal
circumstance.
❖ Limits are set such that deterministic effects
never happen
❖ Limits are set such that chances of stochastic
effects are minimised

36. Types Of Exposure
There are three types of radiation exposure;
Occupational exposure; Which is the exposure incurred at work,
and principally as a result of work.
Medical exposure; Which is principally the exposure of persons
as part of their diagnosis or treatment.
Public exposure; Which includes all other exposures (i.e.
exposure incurred by members of the public from authorized
radiation sources, excluding any occupational and medical
exposure and exposure from natural background radiation). Their
justification (for those of non natural origin) is the general benefit
brought by the use of ionizing radiation in Medicine or Industry.

37. Recommended Dose Limits In Planned
Exposure Situations (ICRP 103)
PublicOccupationalType of limit
1 mSv in a year20 mSv per yearEffective dose
15 mSv
50 mSv
150 mSv
500 mSv
500 mSv
Lens of the eye
Skin
Hands and feet
No limit for medical exposure

38. Radiation Dose Limits
• Old Radiation Dose Limits
– 50 milliSieverts per year (mSv/y) for occupational exposure
– 5 mSv/y for the general public
• New Radiation Dose Limits
– 20 mSv/y for occupational exposure (5 year average) with a
maximum of 50 mSv in any one year
– 1 mSv/y for the general public

39. Dose Limits (Public)
❖ The annual dose limit for a member of
the public (e.g. office worker in room
next door to x-ray) is 1 mSv.
❖ In special circumstances, an effective
dose of up to 5 mSv in a single year
provided that the average dose over
five consecutive years does not exceed
1 mSv per year.

40. Legal Dose Limits – Radiation Workers
• Radiation workers are those exposed to radiation as part of their
occupation
• No benefit – only risk
• Receive high levels of radiation exposure
• Very unlikely for dental
• Require annual health check
• Compulsory dose monitoring

41. Radiation Sources
The major source
of occupational
exposure is
radiation scattered
from the patient

42. The Occupational Exposure Of Women
❖ The basis for the control of the occupational exposure of
women who are not pregnant is the same as that for men
and the ICRP recommends no special occupational dose
limit for women in general.
❖ Once pregnancy has been declared, the conceptus should
be protected by applying a supplementary equivalent dose
limit at the surface of the woman’s abdomen (lower trunk)
of 2 mSv for the remainder of the pregnancy.

43. Pregnant Workers
❖ A female worker should, in becoming aware that she is
pregnant, notify the employer in order that her working
conditions may be modified if necessary.
❖ The notification of pregnancy should not be considered a
reason to exclude a female worker from work; however, the
employer of a female worker who has notified pregnancy
should adapt the working conditions in respect of occupational
exposure so as to ensure that the embryo or fetus is afforded
the same broad level of protection as required for members of
the public.

44. Medical Exposure
❖Medical radiation is the largest radiation source
other than natural background
❖Medical radiation dose accounts for about 95% of
doses from “man-made” sources
❖There are about 2 billion diagnostic x-ray
examinations, 32 million nuclear medicine
procedures and 5.5 million radiation therapy
treatments annually

45. Medical exposure
Exposure incurred by :
• patients as part of their own medical or dental
diagnosis or treatment;
• persons (other than occupationally exposed),
voluntarily helping in the support and comfort
of patients;
• volunteers in a program of biomedical
research involving their exposure.

46. Legal Dose Limits - Patients
• For examinations directly associated
with illness – there are no dose limits

47. Diagnostic Radiology-CT
CT is a relatively high dose
procedure especially multi-slice
CT
• Uses of CT are growing very
rapidly
• In some countries, the relatively
high dose and frequency of use
make CT the largest contributor to
dose from diagnostic examinations.

48. Dose Limitation For Comforters
And Visitors Of Patients (I)
The dose limits should not apply to
comforters of patients, i.e., to
individuals exposed while voluntarily
helping (other than in their
employment or occupation) in the care,
support and comfort of patients
undergoing medical diagnosis or
treatment, or to visitors of such
patients.

49. However, the dose of any such comforter
or visitor of patients should be constrained
so that it is unlikely that his or her dose
will exceed 5 mSv during the period of a
patient's diagnostic examination or
treatment. The dose to children visiting
patients who have ingested radioactive
materials should be similarly constrained
to less than 1 mSv.
Dose Limitation For Comforters
And Visitors Of Patients (II)

50. Some cases are not considered for dose limits, although they may
increase the effective dose:
❖Natural background radiation
❖Origin: cosmic radiation and natural radioactive elements in
the environment (2-3 mSv/year)
❖Radiation received as consequence of medical exposure
❖It may represent an increment of dose > than natural
radiation, but it is not taken into consideration for dose limits.
Not Considered For Dose Limits

51. Aspects Of The Problem
There are four main aspects of the problem to be considered.
▪ Firstly, radiological procedures should be based on a
demonstrated medical need.
▪ Secondly, when radiological procedures are required, it is
essential that patients be protected from excessive radiation
during the exposure.
▪ Thirdly, it is necessary that personnel in radiology departments
be protected from excessive exposure to radiation in the course of
their work.
▪ Finally, personnel in the vicinity of radiology facilities and the
general public require adequate protection.

52. Risk
• The statistical probability that personal injury will
result from some action
– smoking, speeding, extreme sports, ect.
– ionizing radiation exposure

53. Is Radiation Safe?
• Safer than normal risk associated with
many activities encountered daily

54. Average Annual Risk Of Death In The
UK From Industrial Accidents And
From Cancers Due To Radiation Work
Coal mining 1 in 7,000
Oil and gas extraction 1 in 8,000
Construction 1 in 16,000
Radiation work (1.5 mSv/y) 1 in 17,000
Metal manufacture 1 in 34,000
All manufacture 1 in 90,000
Chemical production 1 in 100,000
All services 1 in 220,000
These figures can
be compared to an
estimate of 1 in
17000 for 1.5
mSv/year received
by radiation
workers

55. The following activities are associated with
a risk of death that is 1/1,000,000
•10 days work in a nuclear medicine department
• smoking 1.4 cigarette
• living 2 days in a polluted city
• traveling 6 min in a canoe
• 1.5 min mountaineering
• traveling 480 km in a car
• traveling 1600 km in an airplane
• living 2 months together with a smoker
• drinking 30 cans of diet soda
Risks

56. Expected reduction of life
Unmarried man 3500 days
Smoking man 2250 days
Unmarried woman 1600 days
30% overweight 1300 days
Cancer 980 days
Construction work 300 days
Car accident 207 days
Accident at home 95 days
Administrative work 30 days
Radiological examination 6 days
Risks

57. Comparative Probability Of Death By
Doing Different Activities
Units of deaths per billion with one hour of risk exposure:
• Birth: 80000
• Professional Boxing: 70000
• Alpine Mountaineering: 40000
• Motorcycle racing: 35000
• Canoeing: 10000
• Serving in Vietnam: 7935
• Motorcycle riding: 6280

58. Comparative Probability Of Death By
Doing Different Activities (Cont)
Units of deaths per billion with one hour of risk exposure (cont):
• Swimming: 3650
• Small boat boating: 3000
• Cigarette Smoking: 2600
• Air travel: 1450
• Automobile Travel: 1200
• Hunting: 950
• Coal Mining: 910
• Climbing Stairs: 550

59. Comparative Probability Of Death By
Doing Different Activities (Cont)
Units of deaths per billion with one hour of risk exposure (cont):
• Amateur Boxing: 450
• Being struck by lightning: 200
• Child asleep in crib: 140
• Rail or bus travel in Britain: 50
• Rail or bus travel in USA: 10.0
• Radiation exposure of world population to a local nuclear
conflict: 5.0

60. Comparative Probability Of Death
By Doing Different Activities (Cont)
Units of deaths per billion with one hour of risk exposure (cont):
• Living in an area where snakes are present: 3.8
• Being vaccinated: 1.3
• Giving This lecture: < 1

61. Comparative Probability Of Death By
Doing Different Activities (Cont)
One in a million risk of death from the following:
• 1.5 cigarettes
• Driving 50 miles
• Flying 250 miles
• 1.5 minutes of rock climbing
• 6 minutes of canoeing
• 20 minutes being a man aged 60
• 1-2 weeks of typical factory work

62. What Is The Radiation Risk Estimate?
❖ According to the Biological Effects of Ionizing Radiation
committee V (BEIR V), the risk of cancer death is 0.08% per
rem for doses received rapidly (acute) and might be 2-4
times (0.04% per rem) less than that for doses received over
a long period of time (chronic).
❖ These risk estimates are an average for all ages, males and
females, and all forms of cancer. There is a great deal of
uncertainty associated with the estimate.

63. Risk Estimates
• The risk estimates given in the following table include an
assumption of full expression of the cancer risk and an
assumption of a population distribution over all ages and both
sexes.
• The genetic component includes severe genetic effects for the
first two generations.
• In the total risk coefficient, the somatic risk is 125 × 10-4 Sv-1
(125 × 10-6 rem-1), which for radiation protection purposes is
rounded off to 1 × 10-2 Sv-1 (1 × 10-4 rem-1). The genetic
component of the risk is 40 × 10-4 Sv-1 (0.4 × 10-4 rem-1).

64. Risk Estimates

65. Negligible Individual Risk Level
• An annual effective dose that provides a low-exposure
cut off, below which the individual risk can be
described as negligible.

66. Negligible Individual Risk Level
• A negligible individual risk level (NIRL) is defined by the
NCRP as “a level of average annual excess risk of fatal health
effects attributable to irradiation, below which further effort to
reduce radiation exposure to the individual is unwarranted.”
• The NCRP also states that “the NIRL is regarded as trivial
compared to the risk of fatality associated with ordinary,
normal societal activities and can, therefore, be dismissed from
consideration.”

67. Negligible Individual Risk Level
• The concept of NIRL is applied to radiation protection
because of the need for having a reasonably negligible risk
level that can be considered as a threshold below which
efforts to reduce the risk further would not be warranted or,
in the words of the NCRP, “would be deliberately and
specifically curtailed.”

68. Negligible Individual Risk Level
• To avoid misinterpretation of the relationships between the
NIRL, ALARA, and maximum permissible levels, the NCRP
points out that the NIRL should not be thought of as an
acceptable risk level, a level of significance, or a limit. Nor
should it be the goal of ALARA, although it does provide a
lower limit for application of the ALARA process. The
ALARA principle encourages efforts to keep radiation
exposure as low as reasonably achievable, considering the
economic and social factors.

69. Negligible Individual Risk Level
Example
• Calculate the risk for (a) radiation workers, (b) members
of the general public, and (c) NIRL, corresponding to
respective annual effective dose-equivalent limits.
Assume risk coefficient of 10-2 Sv-1 (10-4 rem-1).

70. Negligible Individual Risk Level
Example
(a)
Annual effective dose equivalent limit for:
Radiation workers = 50 mSv (5 rem)
Annual risk = 5 rem × (10-4 rem-1) = 5 × 10-4

71. Negligible Individual Risk Level
Example
(b)
Annual effective dose equivalent limit for members of:
General public = 1 mSv (0.1 rem)
Annual risk = 0.1 rem × (10-4 rem-1) = 10-5

72. Negligible Individual Risk Level
Example
(c)
Annual effective dose equivalent limit for NIRL:
= 0.01 mSv (0.001 rem)
Annual risk = 0.001 rem × (10-4 rem-1) = 10-7

73. Dealing With Ionizing Radiation
Its risks should be kept in perspective with other risks.

75. Controlled Area
• An area to which access is subject to control and in which
employees are required to follow specific procedures aimed at
controlling exposure to radiation

76. Controlled Area
• Personnel mentoring equipment shall be supplied to each
occupationally exposed individuals 18 years of age, or over,
who enters any controlled area under such circumstances that
individuals is likely to receive in excess of 10% of the above
area dose equivalent limits.

77. Controlled Area
• The concept of a "Controlled Area" localizes radiation use
within the facility, thereby permitting more effective
monitoring and control of potential radiation safety
problems.
• "Controlled Area" shall mean any area the access to which
is controlled for the purpose of protecting individuals from
exposure to radiation.

78. Controlled Area
• Access to controlled areas should be restricted, at least by
the use of warning signs.
• High radiation areas and each radiation area where the
possibility presents of approaching 10% of the
occupational dose limit shall be treated as controlled areas.

79. Controlled Area
The specific requirements are:
1. The area must be secured when it is not occupied by responsible
personnel.
2. The area must be posted with proper signs indicating the radiation
zone(s) and the sources which is present.
3. Personnel monitoring must be provided where appropriate, as
determined by the Radiation Safety Office.
4. Surveys must be performed to maintain surveillance on the hazards
which might be present, and records kept.
5. Personnel must receive written instructions as to the hazards present in
the area.

80. Protection from External Radiation
external hazards arise from
❖radioactive sources
❖machines producing radiation eg x-rays
Protection Methods
fall under three headings
1) Time limit the exposure time
2) Distance use inverse square law
3) Shielding attenuate the beam

81. Practical Methods To Restrict
YOUR Radiation Exposure
•Time
•Distance
•Shielding

82. Reduction of External Dose
❖Minimize the time spent near the radiation source
❖Maximize the distance away from the source
❖Make use of available shielding

83. Time
An ALARA principle is to
reduce the time in a radiation
field
100 200 300 mrem
100 mrem/hr 1 hour 2 hours 3 hours

84. 20
Time
Dose is proportional to
the time exposed
it is wise to spend no more time
than necessary near radiation sources

85. Time
Less time = Less radiation exposure
Obtaining higher doses in order to get an
experiment done quicker is NOT “reasonable”!

86. Time
• minimize time in radiography or fluoroscopy rooms
• minimize time spent with patients who are undergoing therapy
treatment eg. nuclear medicine procedures, radioactive
implants
• Know Your Protocol
➢ Read the procedure through carefully
➢ Understand the steps clearly or
➢ Have the protocol displayed where you can see it
• Practice the technique beforehand

87. Methods For Minimizing Time I
• Pre-plan and discuss the task thoroughly prior to
entering the area.
• Use only the number of workers actually
required to do the job.
• Have all necessary tools before entering the
area.
• Use mock ups and practice runs.
• Take the most direct route to the job site.

88. Methods For Minimizing Time II
• Never loiter in an area controlled for radiological
purposes.
• Work efficiently but swiftly.
• Do the job right the first time.
• Perform as much work outside the area as possible.

89. Distance As A Radiation
Protection Measure
For a point source,
the Radiation Dose
decreases as the
square of the distance
from the source.
Dose  1/d2

90. Distance
Another ALARA principle is to
maximize the distance from source
0 1 2 3 4
ft. ft. ft. ft. ft.
100 25 11 6 mrem/hr
Inverse
square
1 1/4 1/9 1/16

91. Distance
• Operator B receives only a quarter of
the radiation received by Operator A if
he is standing twice the distance from
the source
• Operator B receives only one ninth of
the radiation received by Operator A is
he is standing 3 times the distance
from the source

92. Distance
❖ It is recommended that an individual remains as
far away as possible from the radiation source .
❖ Procedures and radiation areas should be
designed such that only minimum exposure
takes place to individuals doing the procedures
or staying in or near the radiation areas.

93. Consequence
• Distance is very efficient for radiation protection as the dose
falls off in square
• Examples:
– long tweezers for handling of sources
– big rooms for imaging equipment

94. Methods For Maintaining Distance
From Sources Of Radiation
• The worker should stay as far away
as possible from the source of
radiation.
• For point sources, the dose rate
follows the inverse square law. If
you double the distance, the dose
rate falls to 1/4. If you triple the
distance, the dose rate falls to 1/9.

95. • Be familiar with
radiological conditions in
the area.
• During work delays, move
to lower dose rate areas.
• Use remote handling
devices when possible.
Methods For Maintaining Distance
From Sources Of Radiation

96. Shielding

97. Shielding
• Materials “absorb” radiation
• Proper shielding = Less
Radiation Exposure
• Plexiglass vs. Lead

98. Shielding
incident
radiation transmitted
radiation
Barrier thickness

99. Shielding

100. Proper Uses Of Shielding
❖Shielding reduces the
amount of Radiation dose
to the worker.
❖Different materials
shield a worker from the
different types of
radiation.

101. Shielding Examples

102. ◼ Shielding used where
appropriate
◼ Significantly reduces
radiation effects
Lead
Plexiglas
Radiation Shielding

103. Shielding
•Various high atomic number (Z) materials that absorb radiations
can be used to provide radiation protection
•The ranges of alpha and b particles are short in matter the
containers themselves act as shields for these radiations
–Alpha can be stopped by a piece of paper
–Beta low molecular weight element Al or glass can stop its effect.
(Whay don’t we use lead for shielding of beta radiation?)
•Gama radiations are highly penetrating absorbing material must
be used for shielding of g-emitting sources
–Lead is most commonly used for this purpose.

104. Alpha

−−

 ++
Beta
Gamma and X-rays
Neutron
Paper Plastic Lead Concrete


n

 g
Shielding Of Various Types Of Radiation

105. Shielding
• Proper uses of shielding
– Permanent shielding.
– Use shielded containments.
– Wear safety glasses/goggles to
protect your eyes from beta
radiation, when applicable.
– Temporary shielding (e.g., lead
blankets or concrete blocks)
• Only installed when proper
procedures are used.

106. Proper Uses Of Shielding

107. Proper Uses Of Shielding
It should be
remembered that the
placement of shielding
may actually increase
the total dose (e.g.,
man-hours involved in
placement,
Bremsstrahlung, etc.).