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 outer space and the earth itself • Low levels of naturally occurring radioactive material are in our bodies and environment, (e.g., food and building materials) • Some consumer products also contain small amounts of man-made or naturally occurring radioactive material 1

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 2

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

Sources of Ionizing Radiation (World Average), UNSCEAR 2008 Atmospheric Testing 0,2% External Cosmic 15,8% Chernobyl 12,8% 0,1% Internal 9,5% Occupational Medical 0,2% 19,7% Fuel cycle 0,0% Radon Fukushima* 41,4% 0,3% Natural ~80% Medical ~20% Remainder <1% * UNSCEAR 2013 4

Ionizing versus Non-ionizing Radiation 5

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 ) 6

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 After 10 half-lives, very little radioactivity remains 7

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 3.7×10 10 Becquerel’s • Specific Activity – the amount of radioactivity (Bq) per unit mass (usually grams or kilograms) of a radionuclide 9

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) 10

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 w R • US Unit: 1 rem = 0.01 Sv (10 mSv) 11

Radiation Weighting Factors • Heavier particles Radiation w R (alphas, neutrons, and protons), cause Photons 1 more damage in tissue than photons Beta 1 and betas Alpha 20 • An alpha causes Neutron 5 - 20 20 times more damage than a Protons 2 photon Reference: ICRP 60 (International Council on Radiation Protection) 12

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 13

Specific Activity - Example 37 TBq 238 U 37 TBq 226 Ra (3 tonnes) (1 gram) 4.5 × 10 9 years 1600 years Uranium has lower specific activity (1.2 x 10 -4 Bq/g) Radium has higher specific activity (3.7 x 10 10 Bq/g) 14

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 LD 50/30 for irradiation 4500 mSv LD 50/30 is the lethal dose of radiation that causes a mortality rate of 50% of the group exposed within 30 days without medical intervention. 15

External vs. Internal Exposure External Exposure Internal Exposure • Exposure and dose • Dose accumulates occur at same time over time • Dose - relatively • Dose - not uniform uniform over all organs among organs 16

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 17

IAEA GSR Part 3 Radiation Protection and Safety of Radiation Sources: International Safety Standards, General Safety Requirements Part 3 18

Equivalent Dose Limits IAEA GSR-3 (mSv/year) Equivalent Dose Limits Occupational Public Whole Body 20 1 Lens of Eye 20 15 Skin or Extremities 500 50 19

IAEA GSR Part 7 Preparedness and Response for a Nuclear or Radiological Emergency, General Safety Requirements Part 7 20

IAEA Emergency Dose Limits Dose* Tasks (mSv) Life Saving Actions <500 Actions to prevent severe health effects or injuries <500 Actions to prevent development of catastrophic conditions Actions to avert a large collective dose <100 to the public Do not exceed without Incident Commander approval *IAEA GSR-7, Preparedness and Response for a Nuclear or Radiological Emergency, 2015 21

IAEA Public Emergency Guidelines Urgent Protective Action Projected Dose* Sheltering; Evacuation; Prevention of inadvertent ingestion; Restrictions on food, milk, and drinking water; Restrictions on commodities other 100 mSv in first 7 than food; Contamination control; days Decontamination; Registration; Reassurance of the public Protection of Fetus 50 mSv in first 7 Iodine Prophylaxis (dose to thyroid) days * IAEA Preparedness and Response for a Nuclear or Radiological Emergency, GSR-7, 2015 22

IAEA Public Emergency Guidelines Early Protective Action Projected Dose* Temporary relocation; Prevention of inadvertent ingestion; Restrictions on food, milk, and drinking water and restrictions on food chain and 100 mSv in first water supply; Restrictions on year commodities other than food; Contamination control; Decontamination; Registration; Reassurance of the public 100 mSv for Protection of Fetus gestation period *IAEA Preparedness and Response for a Nuclear or Radiological Emergency, GSR-7, 2015 23

Radiation Protection 24

External Hazard Protection Three basic principles to minimize dose from external radiation: 1. Time 2. Distance 3. Shielding 25

Time 100 µSv 64 73 72 71 70 69 68 67 66 65 62 63 75 61 60 59 58 57 56 55 54 53 74 77 76 89 99 98 97 96 95 94 93 92 91 90 88 51 87 86 85 84 83 82 81 80 79 78 52 50 25 19 26 49 24 23 22 21 20 18 29 17 16 15 14 13 12 10 27 28 30 40 48 47 46 45 44 43 42 31 41 39 38 37 36 35 34 33 32 11 4 1 2 3 0 5 6 7 8 9 26

Distance 1 meter 1 meter 1 mSv/hour 0.25 mSv/hour Dose rate falls off as the square of the distance Double the distance - reduce dose rate by a factor of four 27

Shielding Maximize shielding material between the individual and the source to minimize the dose rate 28

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 29

IAEA First Responder Recommendations INITIAL INNER CORDONE SITUATION AREA (Safety Perimeter) OUTDOOR EVENT Unshielded or Damaged 30 meter radius Potentially Dangerous Sources Major Spill from Potentially 100 meter radius Dangerous Source Fire, explosion, fumes involving 300 meter radius potentially dangerous source Suspected bomb (RDD) 400 meter radius or more exploded or unexploded for fragments 30

IAEA First Responder Recommendations INITIAL INNER CORDONE SITUATION AREA (Safety Perimeter) INDOOR EVENT Damage, loss of shielding or Affected and adjacent areas, spill - potentially dangerous including floors above and source below Fire or other event that can Entire building and outside spread material through building area as described above (e.g., thru ventilation system) EXPANSION OF AREA BASED ON RADIOLOGICAL MONITORING Ambient Dose Rate at 1 m Areas greater than 100 above ground µSv/hour 31

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 IAEA Manual for First Responders to a Radiological Emergency, 2006 32

Basic Radiation Concepts and Radiation Protection Questions/Discussion