1. RADIATION PROTECTION PRINCIPLES

2. Contents 1. Introduction 2. Objectives of Radiation Protection
3. Radiation Protection Systems
4. Intervention
5. Protection Against Radiation Hazards
6. References

3. Introduction
Radiation protection principles are related to the source and individual.
There are two systems of radiation protection;
Proposed and continuing practice that cause exposure,
Intervention that reduces exposure.
Both systems are used in three types of exposures, i.e. workers, medical and public.

4. Objectives of Radiation Protection
Prevent the occurrence of deterministic effect by restricting doses to individuals below the relevant thresholds. 2.
Reduce induction of stochastic effect.
Deterministic effect is the effect where the intensity of effect increases with dose. There are thresholds for deterministic effects.
Stochastic effect is the probability of occurrence is proportional to the dose. No threshold can be invoked for them.

5. Radiation Protection Systems
3 Principles used in Radiation Protection Systems:
Justification of Practice
Optimization of Protection and Safety
Dose Limit

6. Radiation Protection Systems
Justification of Practice
In proposed and continuing practices, the justification of practice must be such that the work uses radiation because it gives benefit (or gain) to the exposed individuals or to society that exceeds radiological risk.
Justification in intervention provides more benefit in comparison to if there were no intervention.

7. Radiation Protection Systems
Optimization of Protection and Safety
Based on the principles of ALARA (As Low As Reasonably Achievable).
For any given radiation source within a practice, the magnitude of individual doses, the number of people exposed, and the likelihood of incurring exposures should be kept to as low as reasonably achievable, taking economic and social factors into considerations.

8. Radiation Protection Systems
Dose Limit
Dose limit is used to apply controls on each individual’s accumulation of dose.
Dose limits are not :
a line of demarcation between “safe” and “dangerous”,
the sole measure of the stringency of a system of protection.
Dose limits do not include medical exposures and natural background radiation.

9. Radiation Protection Systems
Annual Dose Limits (ADL)
There are different categories of dose limits for :
radiation workers;
members of the public;
trainees of radiation;
planned special exposures; and
female pregnant workers.

10. Radiation Protection Systems
1. ADL for Occupational Exposure
Application
ADL (mSv)
Annual dose limit for the whole body exposure of worker 20
Female pregnant worker: dose to the foetus accumulated over the period of time between confirmation of pregnancy and the date of birth
< 1
Partial body exposure of a worker :
i. Limit for the effective dose-equivalent
ii. Limit on average dose in each organ or tissue
iii.Limit for lens of the eyes
iv.Limit on equivalent dose for the hands and feet 50
500
150

11. Radiation Protection Systems
2. ADL For Exposure of Members of Public
Application
ADL (mSv)
Dose limit for the whole body exposure 1
Average dose for lens of the eyes 15
Average dose for the skin 50
Effective dose limit for a person who knowingly assits in the support of a patient during the period of diagnostic examination or treatment of the patient
< 5
Effective dose limit for a person below the age of 16 years visiting patient undergoing treatment or diagnostic examination
< 1

12. Radiation Protection Systems In a calendar year (mSv)
3. Dose Limit for Apperentice and Students
Apprentices and students in radiation work (in a supervised or controlled areas) must not be less than 16 years old.
Application
In a calendar year (mSv)
Dose limit for the whole body exposure 6
Average dose for lens of the eyes 50
Equivalent dose to the extremities
150
Equivalent dose to the skin

13. Radiation Protection Systems
Dose Limit in Special Circumstances
Refers to voluntary exposure during normal operation whereby one or more of the annual dose limits for a worker are likely to be exceeded.
Conditions
i. Allowed only in situations when alternative techniques, which do not involve such exposure, cannot be used.
ii. Shall be carried out when approved by the appropriate authorities (i.e. AELB or the Ministry of Health of Malaysia).
iii. Temporary and is subjected to review by the appropriate authorities

14. Radiation Protection Systems
4. Intervention
Intervention is carried out when:
an emergency situation occurred;
a directive issued by appropriate authority in any other temporary exposure situation to reduce or avert temporary exposures;
the appropriate authority directs the remedial action to reduce or avert chronic exposure as specified by them.
The form, extent and duration of intervention shall be optimized to produce the maximum net benefit in the social and economic circumstances.

15. Radiation Protection Systems
5. Protection Against Radiation Hazards
Made based on engineering as well as administrative controls.
One method of control against radiation hazard employing both engineering and administrative controls is through the classification of areas.
Working areas may be classified according to :
clean area,
supervised area &
controlled areas.
Classification of areas take into account the likelihood and magnitude of potential exposures (risk) and the nature and extent of the required protection and safety procedure.

16. Radiation Protection Systems
5. Protection Against Radiation Hazards
... continue
Clean Area
Work area where the annual dose received by a worker is not likely to exceed the dose limit for a member of the public.

17. Radiation Protection Systems
5. Protection Against Radiation Hazards
... continue
Supervised Area
Work area for which the occupational exposure conditions are kept under review even though specific protective measures and safety provisions are not normally needed.
Area is clearly demarcated with radiation warning signs and legible notices clearly posted.

18. Radiation Protection Systems
5. Protection Against Radiation Hazards
… continue
Controlled Area
Work area where specific protection measures and safety provisions could be required for controlling normal exposures or preventing the spread of contamination during normal working condition and preventing or limiting the extent of potential exposures.
Annual dose received by a worker in this area is likely to exceed 3/10 Annual Dose Limit.
Area is clearly demarcated with radiation warning signs and legible notices clearly posted.

19. Radiation Protection Systems
5. Protection Against Radiation Hazards
Control Against External Exposure
Three methods of radiation protections that can be used - shielding, time and distance

20. Radiation Protection Systems
5. Protection Against Radiation Hazards
Shielding
Material may be used to attenuate radiation and thus provide shielding against external exposure.
Shielding takes into consideration
the density and thickness of shielding materials,
the quality of radiation.
Quality of radiation refers to type of radiation, its energy, the flux and dimension of source.

21. Radiation Protection Systems
5. Protection Against Radiation Hazards
Continue ...
Selection of shield depends on the types of radiation.
Alpha particles lose energy rapidly in passage through matter and hence do not penetrate far. No shielding is required against alpha particles.
Beta particles do not lose energy so rapidly compared to alpha particles, and are therefore more penetrating. Materials composed of elements of low atomic number such as Perspex and aluminum and thick rubber are most appropriate for the absorbance of beta particles.

22. Radiation Protection Systems
5. Protection Against Radiation Hazards
Continue ...
Neutrons are uncharged particles and can penetrate matter considerably. Shields use on neutron is directed towards reducing the energy of the neutrons to levels that can easily be absorbed
 Neutron (< 1 MeV)
A reduction of the energy of neutron is best accomplished by collisions with atoms of light elements, e.g. hydrogen.
 Neutrons (> 1 MeV)
Energy of fast neutrons is best reduced using water and paraffin wax. 20 cm of paraffin wax will attenuates 1 MeV fast neutrons by a factor of 10

23. Radiation Protection Systems
5. Protection Against Radiation Hazards
Continue ...
Attenuation of x-and gamma-rays require the use of high atomic number materials. The most suitable material is lead and iron.
In the medium energy range (0.50 – 0.75 MeV) the density of the material is more important than the atomic number. At higher and lower energy ranges, materials of higher atomic number are more effective.

24. Radiation Protection Systems
5. Protection Against Radiation Hazards
Comparison
- types of radiation and shielding required

25. Radiation Protection Systems
5. Protection Against Radiation Hazards
Time
Dose = Dose rate x time
The longer the exposure time the higher is the dose received and vice versa.

26. Radiation Protection Systems
5. Protection Against Radiation Hazards
Distance
Reduction of radiation dose inversely proportional the square of the distance or it follows the inverse square law equation. I1 I2 = d1 d2 2
where I1 and I2 are radiation intensities at distances d1 and d2 respectively.

27. Radiation Protection Systems
5. Protection Against Radiation Hazards
Control of Internal Exposure
Internal exposure is attributed to radiation exposures from radionuclides inside the body.
There are three modes of entry by radionuclides into the body; i.e. inhalation, ingestion and penetration through the skin.
Protection against such radiation hazards may be overcome through:
the use of personal protective equipment,
having proper facilities to handle unsealed sources
having procedures to safely handle them.

28. Radiation Protection Systems
5. Protection Against Radiation Hazards
Radiation Personal Protective Equipment (PPE)
Worn by radiation workers to reduce the risk of radiation exposure from internal radiation exposure and radioactive contamination.
The last line of defense in controlling risk from ionizing radiation.
Since the radiation hazards still exist, PPE should only be used to complement other means of radiation hazard control already in place.

29. Radiation Protection Systems
5. Protection Against Radiation Hazards
... continue
Examples of personal radiation protection equipments/ clothing include:
Laboratory coat
Overall or boiler suit
Rubber gloves
Overshoes
Rubber boots
Breathing apparatus
(example - Pressurized clothing, SCABA + whole body suit (Self Contained Breathing Apparatus))

30. Radiation Protection Systems
5. Protection Against Radiation Hazards
Safety Equipment And Facilities At The Place Of Work
These equipments are not worn by workers but are used by them to reduce exposure and contamination.
Safety facilities include building design incorporating safety features to handle radiation and radioactivity. Examples of such equipment and facilities are:
Remote-handling tongs
Lead brick
Liquid transfer system
Radioactive containers
Ventilated facility

31. Radiation Protection Systems
5. Protection Against Radiation Hazards
Safety Procedures and Surveillance
Handling of unsealed sources increases the risk of internal radiation exposure and contamination.
Safety procedures employed in work related to handling unsealed sources must stress the importance of preventing inhalation, ingestion and penetration of radionuclides through the skin, and contamination of personnel and working areas in normal routine procedure and emergency situations.

32. Radiation Protection Systems
5. Protection Against Radiation Hazards
... continue
Having a safe working procedure does not guarantee its compliance. Surveillance of compliance and monitoring of radiation levels must be carried out periodically. Both visual surveillance and those using radiation monitoring and detectors must be used.

33. Summary

34. Thank You for your attention