1. Basic Radiation Protection for Search Teams

2. Introduction By the end of this module students will be able to:
Explain the two main radiological hazards
List the main methods of controlling these two hazards
Describe the basic radiation protection principles for orphan source search personnel
State the doses and dose rates requiring action on their part

3. Overview Basic radiation protection
Biological effects
Significant doses
External radiological hazard and its control
Internal radiological hazard and its control
Basic radiological surveys
Establishment of controlled areas
Personal protection and dose limits

4. Radiation and radioactive substances are all around us everyday
Cosmic Rays
Food & drink
Radon
Terrestrial gamma rays

5. Threshold for early death
Radiation dose is measured in Sieverts:
Increasing radiation dose (mSv)
1 millisievert (mSv) = 1/1000 Sievert
Threshold for early death
Radiation sickness
Worker annual
dose
limit
Public annual
dose
limit
Chest
x-ray
2 000
1 000 20 1
0.3

6. Examples of Harmful Effects of Radiation
Late effects
e.g.: thyroid and other cancers
Early effects
Radiation
burns
Blood count depression
Hair loss
Radiation sickness
Higher radiation dose = higher risk of getting cancer
(compare to smoking: more cigarettes = higher risk of getting lung cancer)
These ‘deterministic’ effects occur only above a certain (high) radiation dose
Higher dose = worse effect

7. Early Biological Effects of Ionizing Radiation
Dose Received
Resulting Effects
Less than 0.10 Sv
No detectable effects
0.10 – 0.25 Sv
Minor blood changes
1.0 Sv
Temporary sterilization in males
3.0 Sv
GI effects – nausea, vomiting, lining damage
3.0 – 5.0 Sv
Lethal Dose 50% of the population in 30 days (LD50/30)
10.0 Sv
Lethal
50.0 Sv
Central Nervous System – Brain damage, CNS failure

8. Late Biological Effects of Ionizing Radiation
Increased cancer risk of about 5% per Sv (over about 0.1 Sv)
10+ years after exposure
Risk at lower doses is uncertain but probably a bit lower

9. Penetration of Radiation

10. Two Types of Radiation Exposure
Exposure from a radiation source outside the body (external hazard)
Exposure due to inhaling or ingesting radioactive material (internal hazard)

11. Control of External Exposure
Spend less time
in the radiation
(½ time = ½ dose)
Move away from the radiation
(Double distance = ¼ dose)
Use shielding

12. As Low As Reasonably Achievable
So, while performing search activities keep radiation exposure As Low As Reasonably Achievable (ALARA)
Minimize time in the area
Maximize distance from the source
Use shielding if possible

13. Time You will have to spend time in the area searching for the source
Move smartly and efficiently
Do not loiter in areas of elevated dose rates
Reduce the time in the area by one half and receive half the radiation exposure

14. Distance
Even with sensitive search instruments you will have to be in close proximity of low activity or shielded sources
Unless actively performing work with or near sources move away to reduce radiation exposure
e.g. Move away to discuss next actions
Double your distance from the source and reduce exposure to one quarter
Use long handled tools
Use long handled instruments

15. Increase Distance Do not pick it up 0.25 mSv/hr @ 2 m 1 mSv/hr @ 1 m
If one assumes that a source of gamma or X-rays occupies a single point, it can be shown mathematically that the dose rate at distance d from the source varies inversely with the square of the distance from the source. Doubling the distance from a radiation source decreases the dose rate by a factor of 4. Increasing the distance by a factor of 3 decreases the dose rate by a factor of 9, etc.(it means, it is indirectly proportional to distance quadrate)
Do not pick it up m
1 1 m

16. Shielding
Shielded sources will be harder to detect when performing the search
Radiation exposures can be reduced by shielding found high activity sources
Denser materials make better shields
Improvise with materials available
Stand behind buildings, vehicles, rocks

17. Control of Internal Exposure Hazard
Cannot apply time, distance and shielding once the radioactive material is inside the body
Small quantities become more significant because the body is committed to a certain dose once it is inside
Hence preventing it getting inside is the most important control for loose radioactive material – contamination

18. Control of Internal Exposure Hazard
Therefore containment is the key:
Access control and protective equipment
Control access to potential sources of contamination
Wear proper protective equipment

19. Protection Against Internal Exposure
Perform frequent surveys
No eating, drinking, smoking in potentially contaminated areas
Keep hands away from mouth
Cover open wounds
In case of risk, immediately avoid contact and keep hands and other objects away from the mouth, respectively use available protection for the mouth( e.g. wet piece of cloth etc.)

20. Protective Clothing Protective clothing appropriate to the situation
Level depends on quantity and type of actual or suspected contamination
Shoe covers, lab coat, gloves
Boots, coveralls and gloves
Fully enclosed waterproof hazmat suit with supplied air

21. Inhalation Protection Equipment
Respirators
Dust filters (little value)
Half-face/ full-face respirator (OK)
Self contained breathing apparatus (excellent)
There are different types of protective tools and respirators to minimize the inhalation of aerosols and dust containing radioactive substances. Some filters may have specific characteristics and can absorb typical chemical radioisotopes.

22. Dosimetry
Search team members need to wear dosimetry to record radiation exposures received while performing searches and consideration should be given to the following
Whole body dosimeters for recording dose of record
Alarming secondary dosimeters that provide real time indication of dose
Extremity dosimeters

23. Radiological Surveys Characterize the radiological environment:
Radiation dose rates
Types of radiations
Always check gamma, then others if suspected (Alpha, beta, neutron)
Contamination levels
Types of contamination
Surface or airborne
Alpha, beta, gamma

24. Radiation Surveys Turn on and checkout instrument away from area
Ensure that dose rate at current location is background or at an acceptable low level
Move towards suspected radiation with instrument on

25. Contamination Surveys
Direct vs. Indirect
Direct: only in low background radiation
Direct: with instrument, measure count rate near the ground or surface of interest
Must use indirect if higher background
Indirect: take swipe or small sample of surface material (dirt) and count it in a low background area

26. Establishment of Controlled Areas
Set up controlled access to:
Areas of higher radiation
Areas that are, or may be, contaminated
Areas where security needs to be maintained
Only one entry/exit point so stay times and contamination can be managed

27. Controlled Area for Major Event

28. Inner Cordoned Area (1/2)
SUGGESTED RADIUS OF INNER CORDONED AREA FOR RADIOLOGICAL EMERGENCIES (Safety Perimeter)
Situation
Initial inner cordoned area
(safety perimeter)
Initial determination - Outside
Unshielded or damaged potentially dangerous source
30 m around
Major spill from a potentially dangerous source
100 m around
Fire, explosion or fumes involving a potentially dangerous source
300 m radius
Suspected bomb( potential RDD) exploded or unexploded
400m radius or more to protect against an explosion
Instruction 1 Table 4 contained in IAEA-EPR-First Responders provides general guidance on the radius for the establishment of an initial inner cordoned area. There are sections within the table for emergencies that are outside and for emergencies that occur inside of a building. If you know the radiological emergency situation, an initial radius of the inner cordoned area can be selected and then established.
Examples:
Given a dangerous source is involved in a major spill, what would be the initial radius established for the inner cordoned area?
Lecturer, point to the answer with laser pointer to find the answer: Answer is the area of the spill plus 100 meters around the area of the spill.

29. Inner Cordoned Area (2/2)
SUGGESTED RADIUS OF INNER CORDONED AREA) FOR RADIOLOGICAL EMERGENCIES (Safety Perimeter)
Situation
Initial inner cordoned area
(safety perimeter)
Initial determination - Inside a building
Damage, loss of shielding or spill involving a potentially dangerous source
Affected and adjacent areas
(including floors above and below)
Fires, suspected RDD or other event involving a potentially dangerous source that can spread materials in the building
Entire building and appropriate outside distance indicated
Expansion based on radiological monitoring
Ambient dose rate of 100 μS/h
Where these levels are measured
Note for lecturer: review this table with the participants.

30. Summary for Individuals
Wear proper dosimetry
Whole body dosimeter
Alarming secondary dosimeter
Extremity dosimeter
Wear proper protective equipment (as needed)
Gloves
Coveralls
Boots (or easily decontaminated footwear)

31. Summary for Individuals
Carry appropriate radiation/contamination detectors – or be with someone who does
Observe appropriate controls in and out of controlled access areas
Know the radiation doses and dose rates that require action

32. Individual Dose Limits

33. Summary Radiological hazards and personal protection
Specific applications of these to source search personnel