2. DOSE LIMITS
The prescribed dose limits for an exposures from ionizing radiations for workers
and the members of the public are given below.
General terms used are
The limits on effective dose apply to
the sum of effective doses from
external as well as internal sources.
The limits exclude the exposures
due to natural background radiation
and medical exposures.
Calendar year shall be used for all
prescribed dose limits.
3. Occupational Dose Limits
•Occupational Workers
•Apprentices and Trainees
Occupational Workers
The occupational exposures of any worker should be
controlled and the following limits are not exceeded:
Limits given above apply to female workers also. However, once pregnancy is declared the
equivalent dose limit to embryo/fetus shall be 1 mSv for the remaining period of the
pregnancy
an effective dose of 20 mSv/yr averaged over five consecutive
years
an effective dose of 30 mSv in any year
an equivalent dose to the lens of the eye of 150 mSv in a
year(Equivalent dose is a dose quantity H representing the stochastic health effects of low levels of ionizing
radiation on the human body which represents the probability of radiation-induced cancer and genetic damage.)
an equivalent dose to the extremities (hands and feet) of 500
mSv in a year
an equivalent dose to the skin of 500 mSv in a year
4. Apprentices and Trainees
The occupational exposure of apprentices and trainees between 16
and 18 years of age should be controlled and the following limits should
not be exceeded:
an effective dose of 6 mSv in a year
an equivalent dose to the lens of the eye of 50 mSv in a year
an equivalent dose to the extremities (hands and feet) of 150
mSv in a year and
an equivalent dose to the skin of 150 mSv in a year.
5. • an effective dose of 1 mSv in a year
• an equivalent dose to the lens of the eye of 15 mSv
in a year
• an equivalent dose to the skin of 50 mSv in a year
Dose Limits for Members of the Public
The estimated average doses to the relevant members of the public shall not
exceed the following limits:
Occupational
Workers
Trainees Public
Whole Body-
Effective Dose
20 mSv 5mSv 1mSv
Lens of Eye 150mSv 50mSv 15mSv
Skin 500mSv 150mSv 50mSv
Hand, Fore arms,
Feet and Ankles
500mSv 150mSv 50mSv
6. Protective Materials for X and Gamma Radiation
Lead
Lead is one of the most effective and commonly
used materials for shielding against X-rays and
gamma radiation.
Its high density allows for effective absorption of
radiation.
Lead aprons are often worn by healthcare
professionals during X-ray procedures to protect
against scattered radiation.
Protection against X-rays and gamma radiation is essential in various fields, including
medical imaging, nuclear power, and industrial applications.
When selecting shielding material, it’s important to consider space, source strength
and attenuation.
Lead is usually associated with toxicity concerns, but it’s not a problem once it is sealed
inside the walls. Lead is stable and doesn’t release any toxic gases.
7. Concrete:
Lead is an ideal material for smaller spaces but for
high doses, you should choose a high-density
concrete.
High-density concrete is another effective
shielding material.
It contains heavy elements like barium and
bismuth, which help absorb and attenuate
radiation.
Concrete is commonly used in the
construction of radiation shielding walls and
barriers.
Today, the main shielding materials used in
construction include gypsum, lead or drywall and
concrete, which often includes added materials to
increase the attenuation.
8. Lead glass, also known as leaded glass, contains
lead oxide and is used in windows for areas
where X-ray or gamma radiation is present.
It provides visibility while offering radiation
protection.
Human eyes are 4 times more sensitive to
radiation than other parts of your body.
With the increase in occurrences of early onset
cataracts, lead glasses are now important in
every procedure
Lead Glass:
Steel:
Steel is often used as a structural material for
shielding applications.
While not as effective as lead or concrete, it can
still provide some degree of protection.
9. Tungsten is a dense metal that is effective in
attenuating X-rays and gamma radiation.
Tungsten is a preferred material for radiation
shielding in medical and industrial settings.
It's effective for gamma-ray shielding because it's
hard and only one-third the thickness of lead.
Tungsten:
Tungsten's high density also allows designers to reduce the thickness of shielding
while still achieving the same level of protection.
Tungsten carbide has high potential to replace lead as new lead-free radiation
shielding material in nuclear medicine.
10. Lead is less expensive than Tungsten
Lead is more vulnerable because it is soft
To prevent exposure, lead may need to be
encapsulated or coated
Lead can be cast while Tungsten cannot
Less tungsten is required to provide a certain
attenuation
Difference Between Lead and Tungsten
Polyethylene is a type of plastic that is effective
in attenuating neutrons and gamma radiation.
It is used in some applications, particularly in
nuclear power plants.
Boronated polyethylene is a composite material
that combines polyethylene with boron,
providing enhanced neutron shielding capability.
Polyethylene:
Boron Mixed Polyethylene
11. Radiation Shielding Fabrics:
Special fabrics containing lead or other
radiation-absorbing materials are used in some
applications, such as protective clothing for
radiologic technologists.
Water:
Water is also effective in attenuating
radiation.
It is used in some applications, such as in
spent fuel pools at nuclear power plants.
water provide protection from penetrating
gamma rays
A 7 cm layer of water can reduce the amount of ionizing radiation that passes through it by
half. The remaining radiation is captured or moderated to non-ionizing energy levels, primarily
heat.
The choice of shielding material depends on factors such as the type and energy of the radiation,
the intensity of the radiation source, and the specific requirements of the application.
