Basic Radiation Concepts and Radiation Protection Radiation and - - PowerPoint PPT Presentation

Basic Radiation Concepts and Radiation Protection

Radiation and Radioactive Material Are Part of Our Lives

• We are constantly exposed to

low levels of radiation from

• uter space and the earth itself
• Low levels of naturally
• ccurring radioactive material

are in our bodies and environment, (e.g., food and building materials)

• Some consumer products

also contain small amounts

• f man-made or naturally
• ccurring radioactive material

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Radioactive Material Use In Industry

• We may also encounter

radioactive materials used in various industrial settings, including:

• Nuclear Power
• Radiography
• Soil Moisture/Density

Gauge

• Well-Logging
• Nuclear Medicine

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Radiation Exposure Worldwide

The average annual dose to the world population from all sources of radiation is estimated to be 3 mSv/year. (UNSCEAR 2008)

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UNSEAR – United Nations Scientific Committee on the Effects of Atomic Radiation

Sources of Ionizing Radiation (World Average), UNSCEAR 2008

Fuel cycle 0,0% Chernobyl 0,1% Atmospheric Testing 0,2% Occupational 0,2% Fukushima* 0,3% Internal 9,5% Cosmic 12,8% External 15,8% Medical 19,7% Radon 41,4%

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Natural ~80% Medical ~20% Remainder <1%

* UNSCEAR 2013

Ionizing versus Non-ionizing Radiation

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Types of Ionizing Radiation

• Four basic types of radiation of interest in

radiation safety: 1) Alpha () 2) Beta () 3) Photons

– Gamma () – X-ray (X)

4) Neutron (η)

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Radioactivity Half-Life

• The half-life is the time required for a radioactive

substance to lose half of its radioactivity

• Half-lives range from very short

seconds/minutes/hours to billions of years

• Examples:

Tc-99m 6 hours I-131 8 days Co-60 5.3 years Cs-137 30 years Pu-239 24,400 years U-238 4,500,000,000 years

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After 10 half-lives, very little radioactivity remains

WHY WE NEED RADIATION DETECTORS? (Little Red Riding Hood) None of the natural’s sensors are useful for radiation detection:

• Sight (vision),
• Hearing (audition),
• Taste (gustation),
• Smell (olfaction),
• Touch (somatosensation).

Grandma, what big eyes you have ... It's to see you better, my granddaughter ... Grandma, what long nose do you have ... It's supposed to smell better ...

Radioactivity Units

• Becquerel (Bq) – a unit of radioactivity equal to 1

disintegration (or transformation) per second

• Curie (Ci) – a unit of radioactivity equal to

3.7×1010 Becquerel’s

• Specific Activity – the amount of radioactivity

(Bq) per unit mass (usually grams or kilograms)

• f a radionuclide

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Radiation Absorbed Dose

• Absorbed Dose: energy (Joules) absorbed in

matter per unit mass or kilogram (kg) of material

• International Unit: Gray (Gy) = 1 J/kg
• US Unit: 1 Rad = 0.01 Gray (10 mGy)

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Radiation Equivalent Dose

• Equivalent Dose: absorbed dose in tissue is

multiplied by a “Radiation Weighting Factor” (or Quality Factor) dependent on the radiation type

• International Unit: Sievert (Sv)

Sievert = Gray (Gy) x wR

• US Unit: 1 rem = 0.01 Sv (10 mSv)

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Radiation Weighting Factors

Radiation wR Photons 1 Beta 1 Alpha 20 Neutron 5 - 20 Protons 2

Reference: ICRP 60 (International Council on Radiation Protection)

• Heavier particles

(alphas, neutrons, and protons), cause more damage in tissue than photons and betas

• An alpha causes

20 times more damage than a photon

Specific Activity

• The amount of radioactivity is not related to

the physical size of the source

• Specific activity is the amount of radioactivity

found in a gram of material

• Radioactive material with long half-lives have

low specific activity

• Radioactive material with short half-lives have

high specific activity

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Specific Activity - Example

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37 TBq 238U (3 tonnes) 4.5 × 109 years 37 TBq 226Ra (1 gram) 1600 years

Uranium has lower specific activity (1.2 x 10-4 Bq/g) Radium has higher specific activity (3.7 x 1010 Bq/g)

Radiation Doses in Perspective

Source Dose Natural background radiation 2.4 mSv/year Diagnostic chest x-ray 0.1 mSv Airplane flight 0.05 mSv/hour Smoking 1 pack/per day (effective) 0.36 mSv/year Diagnostic heart catheterization 7 mSv Mild acute radiation sickness 1000 mSv LD50/30 for irradiation 4500 mSv

LD50/30 is the lethal dose of radiation that causes a mortality rate of 50% of the group exposed within 30 days without medical intervention.

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External vs. Internal Exposure

External Exposure

• Exposure and dose
• ccur at same time
• Dose - relatively

uniform over all organs Internal Exposure

• Dose accumulates
• ver time
• Dose - not uniform

among organs

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Dose Limits

• Whole body dose limits established to ensure

no acute dose effects, and minimize long- term increased probability of cancer

• Eye and skin dose limits established below

the threshold for acute dose effects

IAEA GSR Part 3

Radiation Protection and Safety of Radiation Sources: International Safety Standards, General Safety Requirements Part 3

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Equivalent Dose Limits

Equivalent Dose Limits IAEA GSR-3 (mSv/year) Occupational Public Whole Body 20 1 Lens of Eye 20 15 Skin or Extremities 500 50

IAEA GSR Part 7

Preparedness and Response for a Nuclear or Radiological Emergency, General Safety Requirements Part 7

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IAEA Emergency Dose Limits

*IAEA GSR-7, Preparedness and Response for a Nuclear or Radiological Emergency, 2015

Tasks Dose* (mSv) Life Saving Actions <500 Actions to prevent severe health effects

• r injuries

Actions to prevent development of catastrophic conditions <500 Actions to avert a large collective dose to the public <100

Do not exceed without Incident Commander approval

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IAEA Public Emergency Guidelines

*IAEA Preparedness and Response for a Nuclear or Radiological Emergency, GSR-7, 2015

Urgent Protective Action Projected Dose* Sheltering; Evacuation; Prevention

• f inadvertent ingestion; Restrictions
• n food, milk, and drinking water;

Restrictions on commodities other than food; Contamination control; Decontamination; Registration; Reassurance of the public 100 mSv in first 7 days Protection of Fetus Iodine Prophylaxis (dose to thyroid) 50 mSv in first 7 days

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IAEA Public Emergency Guidelines

Early Protective Action Projected Dose* Temporary relocation; Prevention of inadvertent ingestion; Restrictions

• n food, milk, and drinking water

and restrictions on food chain and water supply; Restrictions on commodities other than food; Contamination control; Decontamination; Registration; Reassurance of the public 100 mSv in first year Protection of Fetus 100 mSv for gestation period

*IAEA Preparedness and Response for a Nuclear or Radiological Emergency, GSR-7, 2015

Radiation Protection

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External Hazard Protection

Three basic principles to minimize dose from external radiation:

• 1. Time
• 2. Distance
• 3. Shielding

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Time

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 µSv

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Distance

Dose rate falls off as the square of the distance Double the distance - reduce dose rate by a factor of four

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1 meter 1 meter 1 mSv/hour 0.25 mSv/hour

Shielding

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Maximize shielding material between the individual and the source to minimize the dose rate

Internal Exposure

• Approaches to control internal exposure:

– Avoid inhalation of particulate radiation – Avoid ingestion of radioactive material – Prevent absorption of radioactive material through the skin by cleaning contaminated areas as soon as possible – Clean wounds and punctures of radioactive material and close them to prevent internalizing the contamination

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IAEA First Responder Recommendations

SITUATION INITIAL INNER CORDONE AREA (Safety Perimeter) OUTDOOR EVENT

Unshielded or Damaged Potentially Dangerous Sources 30 meter radius Major Spill from Potentially Dangerous Source 100 meter radius Fire, explosion, fumes involving potentially dangerous source 300 meter radius Suspected bomb (RDD) exploded or unexploded 400 meter radius or more for fragments

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IAEA First Responder Recommendations

SITUATION INITIAL INNER CORDONE AREA (Safety Perimeter)

INDOOR EVENT Damage, loss of shielding or spill - potentially dangerous source Affected and adjacent areas, including floors above and below Fire or other event that can spread material through building (e.g., thru ventilation system) Entire building and outside area as described above EXPANSION OF AREA BASED ON RADIOLOGICAL MONITORING Ambient Dose Rate at 1 m above ground Areas greater than 100 µSv/hour

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IAEA First Responder Recommendations

• Additional Guidance

– Areas greater than 100 mSv/hour should only be entered for life-saving or other time critical actions – limit stay time to 30 minutes – Areas greater than 1000 mSv/hour (1 Sv/hour) – do not enter unless directed by a radiological assessor

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IAEA Manual for First Responders to a Radiological Emergency, 2006

Basic Radiation Concepts and Radiation Protection Questions/Discussion