different aspects of radiation protection

1. Radiation Protection(radiation
units)
Presenter
Dr. SANDIP BARIK
Moderator
Dr. N K PAINULY
Mr NAVIN SINGH

2. Radiation protection
 Radiation protection is the protection of the people
from harmful effects of ionized radiation which
include both particle radiation and high energy
electromagnetic radiation.

3.  Sources of Radiation Exposures
◦ Occupational
◦ Non-occupational
 Naturally occurring sources
 Radon
 Sources in the human body
 Sources in earth’s crust (terrestrial)
 Cosmic radiation
 Manmade sources Medical radiation
 Building materials Atmospheric testing of nuclear
weapons.
 Industrial sources

4. The Biological Effects Of
Radiation
 Prompt personal effects
 Delayed personal effects
 Racial effects

5.  PROMPT PERSONAL EFFECTS
 On receiving very large doses
 Occurs within few hours or days
 Symptoms associated are erythema,vomiting.diarrhoea
 A single dose of 500 rad could result in death

6.  DELAYED PERSONAL EFFECTS
 Chronic low dose irradiation over a considerable period of
time or few exposures giving a high dose
 Clinical Features
 Scaling ,warty growth on hands
 Skin cancer
 Thyroid cancer
 Cataract formation
 Bone marrow compromise leading to fatal anaemia and
leukaemia
 Premature ageing
 Growth and development of fetus and young children

7.  RACIAL EFFECTS
 Effect is produced in the long run and may be far more
important than any purely personal injury
 Occurs mainly due to changes produced by radiation in
hereditary materials
 The harmful effects of radiation are classified into stochastic
effects and non stochastic effects

8. Health risk Estimated Loss of Life
Expectancy
Smoking 20 cigarettes a day 6 years
Overweight by 15% 2 years
Alcohol consumption (U.S. Average) 1 years
Agricultural accidents 320 days
Construction accidents 227 days
Auto accidents 207 days
Home accidents 74 days
Occupational Radiation dose (1 rem/yr), from 51 days
age 18 – 65 (47 rem total)
All natural hazards (hurricane, earthquake, 7 days
flood)
Medical radiation 6 days

9. Stochastic effect Non stochastic effect
 Is one in which the probability  Is one in which severity
of occurrence increases with increases with increase in
increasing absorbed dose. absorbed dose in affected
indivisuals
 The severity in affected
indivisuals dose not depend  Have definite threshold levels
on magnitude of absorbed of radiation dose
dose
 Have no threshold levels of
radiation dose,all or none
phenomenon.

10. PERMISSIBLE DOSES
 Regulating Bodies
 One of the first bodies involved in regulating radiation
hazards is the ICRP (international commission on radiation
protection)
 In U.S the regulatory board is the NCRP(National council on
radiation protection and measurements)
 In India the board is the AERB(Atomic energy regulatory
board)
 Constituted in Nov 15,1983.
 Headquarters in Mumbai.

11. Permissible doses cont…
 ICRP has recommended a series of maximum permissible
dose(MPD) for different body tissues.
 The quoted values are maximum and every effort should be
made to keep the doses to absolute minimum.
 The dose for general public are set at1/10 th of maximum
possible dose for corresponding tissues
 ICRU has also recommended maximum values for amounts
of different radioisotopes which can be deposited in the body
without constituting radiation hazards

12. M.P.D. FOR SOME IMP.
RADIOISOTPOES
RADIOACTIVE ISOTOPE M.P.D. IN µCi
TRITRIUM 1000
CARBON- 14 300
P -32 6
Fe -59 20
Iodine-131 0.7
Ra-226 0.1
Californium-252 0.01

14. Radiation units
 The quantity used are:
 Activity
 Exposure
 Absorbed dose
 Equivalent dose
1) a

15. Activity
 Amount of radioactivity material expressed as the nuclear
transformation rate
 Conventional unit: curie
 SI unit:Bequerel
 1 curie=3.7* 1010 Bq

16. Exposure
 Amount of ionization per mass of air due to x and gamma
rays
 The ICRU defines exposure (x) as quotient of dQ by dm
where dQ is the absolute value of total charge of ions of one
sign produced in air when all the electrons liberated by
photons in air of mass dm are completely stopped in air..
 X=dQ/dm
 Conventional units: Roentgen®
 SI unit:c/kg
 1R=2.58*10-4 c/kg

17. ROENTGEN
 Roentgen was defined as 1R=1 electrostatic
unit(esu)/cm3 air at standard temp and
pressure(STP)
 Current definition is 1R=2.58 *10-4 C/kg air is
equivalent to original if charge is expressed in
Coulombs(1 esu=3.333*10-10 C) and the volume of
air is changed to mass

18. Absorbed dose
 Amount of kinetic energy imparted by radiation per unit mass.
 Conventional unit: radiation absorbed dose(rad)
 SI unit :Gray(Gy)
 100 rad=1 Gy

19. Dose Equivalent
 Biologic effects of radiation depend not only on
dose but also on the type of radiation.
 The dosimetric quantity relevant to radiation
protection is dose equivalent.
 A measure of radiation specific biological damage
in man.
 H=D*Q(D is absorbed dose)(Q is quality factor for
radiation )

20. Dose equivalent
Conventional unit :Roentgen equivalent in man(rem)
SI unit is Sivert
1rem=10 Sivert
RADIATION Q.F.
X-rays & gamma rays 1.0
Electron (incld. β-rays) of energy 1.0
>30kv
Thermal ( slow) neutron 5
Fast neutrons 20

21. Effective dose equivalent
 Whole body exposures are rarely uniform.
 Tissues vary in sensitivity to radiation induced effects
 Effective dose is a measure of radiation and organ system
specific damage in man
 The effective dose equivalent H E=Sum of WT*HT
 Wt=weighing factor of tissue t
 Ht= mean dose equivalent received by the tissue t

22. Effective dose equivalent limits
 NRCP recommendation on exposure limits of radiation
workers are based on following criteria.
a) At low radiation levels the nonstochastic effects are
esentially avoided.
b) The predicted risk factor for stochastic effects should not be
greater than the average risk of accidental death among
workers in safe industries.
c) Safe industries are defined as those having an associated
annual fatality accident rate of 1 or less per 10,000 workers.
d) The ALARA principle should be followed for which the risks
are kept as low as reasonable achievable.

23. ALARA concept
◦ ALARA stands for As Low As Reasonably Achievable.
◦ Because some risk, however small, exists from any
radiation dose, all doses should be kept ALARA.
◦ Includes reducing both internal and external radiation dose.
◦ ALARA is the responsibility of all employees.

24. Dose limits for pregnant women
 The total dose equivalent limited to fetus is 5 mSv(0.5 rem)
 Exposure not exceeding 0.5mSv(0.05 rem) in any 1 mths
If the dose equivalent to the embryo/fetus is
determined to have already exceeded 500
mrem when a worker notifies her employer of
her pregnancy, the worker shall not be
assigned to tasks where additional
occupational radiation exposure is likely during
the remainder of the pregnancy.

25. Conclusion
 The dosimetric quantity relevant to radiation protection is the
dose equivalent.
 Harmful effects of ionizing radiation are classified as
stochastic and non stochastic.
 Effective dose equivalent limits for occupational and general
population has been recommended by the regulatory board
of that country
 The values quoted for radiation workers are such that the
hazards that the doses represent to health is small
compared with ordinary hazards of life
 A radiation worker is far more likely to be involved in a motor
car accident an to suffer from ill effects of radiation,even if
receiving the MPD.

26.  THANK YOU