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Atomic Structure & Radiation

Atomic Structure & Radiation. Community Environmental Monitoring Program CEMP. Gary M. Sandquist, PhD, CHP, PE 2011 Training Session. CEMP Training Outline. Basic Atomic Structure Introduction to Radioactivity Radiation Sources Biological Effects Radiation Risks Radiation Limits.

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Atomic Structure & Radiation

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  1. Atomic Structure & Radiation Community Environmental Monitoring Program CEMP Gary M. Sandquist, PhD, CHP, PE 2011 Training Session

  2. CEMP Training Outline • Basic Atomic Structure • Introduction to Radioactivity • Radiation Sources • Biological Effects • Radiation Risks • Radiation Limits

  3. CEMP Training Outline • Personnel Monitoring • ALARA Program • Radiation Posting & Control • Radiation Work Permits • Radiological Emergencies

  4. CEMP Training Outline • Radioactive Waste Minimization • Radiation Contamination Control • Practical Exercise

  5. Isotopes • ISOTOPES: Atoms with same number protons (same atomic number) but different number of neutrons in nucleus (Mass number different but not atomic #) • 238U versus 235U – atomic # = 92 Chemistry of isotopes identical! 238U same chemistry as 235U

  6. Stable & Unstable Atoms • Only certain combinations of neutrons & protons are stable nuclei. • Too many or too few neutrons for same number of protons then nucleus has excess energy & is unstable. • Unstable atoms become more stable by reducing excess energy through release of radiation. • Unstable nuclei known as radioactive atoms.

  7. Radiation Symbol - Radioactivity

  8. PHYSICAL CHARACTERISTICS Large mass 2 protons, 2 neutrons no electrons Positive charge +2 Highly charged particle emitted from nucleus of atom. Positive charge +2 causes alpha particle (+) to strip electrons (-) from nearby atoms as it passes through material, thus ionizing these atoms. SHIELDING Stopped by outer layer of skin, few centimeters of air or one sheet of paper. BIOLOGICAL HAZARD No external radiation hazard. Internally deposits large amount of energy in small volume of body Alpha Particles ( He4 )

  9. PHYSICAL CHARACTERISTICS Small mass emitted from nucleus of atom with electrical charge of -1. Cause ionization by displacing electrons from their orbits. Same as electron. Ionization caused by repulsive force between beta particle (-) & electron (-); RANGE Limited penetrating ability (< 10 feet in air) because of negative charge. SHIELDING Most beta particles shielded by plastic, glass, metal foil, safety glasses BIOLOGICAL HAZARD An internal hazard due to short range. Hazardous to skin & eyes. Beta Particles ( e-1 or e+1 )

  10. PHYSICAL CHARACTERISTICS Electromagnetic wave or photon with no electrical charge. Gamma rays similar to x rays, but from nucleus. Gamma/x ray radiation ionizes by direct reaction with orbital electrons. Energy of gamma/x ray radiation transmitted directly to target. RANGE Gamma/x rays have no charge or mass Very penetrating Range in air - few hundred feet. SHIELDING Best shielded by dense materials (concrete, lead or steel). BIOLOGICAL HAZARD Produces radiation exposure to whole body. Gamma/X Rays ( g or x )

  11. Activity UnitsDisintegrations Per Unit Time • Traditional (US) unit is Curie • 1 Ci = 3.7 x 1010 dps (dis/sec) • 1 Ci = 2.22 x 1012 dpm (dis/min) • 1 Ci = 1 x 1012 pCi • 1 Ci = 37 GBq • International unit is Becquerel • 1 Bq = 1 dps = 2.70 x 10-11 Ci • 1 GBq = 0.0270 Ci

  12. Radiation Dose Units • rad = 100 ergs/gram of absorber -(Gray) • mrad = 1/1000th of rad • rem = rad x Quality Factor -(Sievert) • Quality Factors • alpha = 20 • beta = 1 • gamma = 1 • neutron ~ 10(avg) varies 2 to 20

  13. Radioactive Half-life • Time for 1/2 of radioactive atoms to decay to something else • Example: 1 Ci X-365 has half life of 1 yr: How much after 2 yrs, 10 yrs, 20 yrs? X(1 yr) = X(0) x (1/2)n with n=2 So activity X(2 yr) = X(0) x (1/2)2 =1/4 X(0) X(10 yr) = X(0) x (1/2)10 ~ 1/1000 X(0) X(20 yr) = X(0) x (1/2)20 ~ 1/million X(0)

  14. Natural Sources (2006 NCRP) • Cosmic radiation ~ 5% • Terrestrial radiation ~ 3% • Internal radiation ~ 5% • Radon / Thoron ~ 37 %

  15. Man-Made Sources • Medical radiation ~ 48% • Nuclear weapon tests < 0.1% • Consumer products ~ 2% • All energy production & research < 0.1% or < 0.5 mrem • Industrial uses < 0.1% • Fukushima < 1 foot elevation

  16. Medical Radiation • X-rays - medical (CT’s, etc) & dental • Radioactive material for diagnosis 131I, 99Tc, 32P, 3H, 14C • Radioactive material for therapy 60Co, 137Cs, 226Ra, neutrons • Annual dose ~298 mrem ~48% total

  17. Average Total Annual Dose 620 mrem Total average US rad exposure (NCRP report 160 - 2006) Prior US level - 360mrem

  18. Radiation Damage • Direct Effects: • Ionization can break chemical bonds • Indirect Effects: • Ionized water results in radicals H+ or HO- or H2O2 • These radicals cause chemical damage • Location of damage important: Cell Nucleus or Cytoplasm

  19. Possible Effects on Cells • No damage evident • Damage repaired & cell normal • Damage not repaired & cell functions abnormally • Cell dies

  20. Cell Sensitivity • Cells have different rad sensitivity • Most sensitive: Cells actively dividing (e.g., stem & blood cells) • Moderate sensitive: Less specialized cells • Least sensitive: Specialized cells or less actively dividing (nerve, brain, bone, muscle cells, skin )

  21. Dose Rate Effects • Acute: Large dose over short time • 10-25 rem slight blood changes • 300-500 rad hematopoetic syndrome • 500-1000 rad GI syndrome • >1000 rad CNS syndrome • Chronic: Low dose rate over long time e.g., Background radiation

  22. Factors for Biological Damage • Total dose (how much) • Dose rate (how fast) • Type of radiation (alpha, beta, gamma, neutron) • Area exposed (total body, internal, hands, etc.) • Cell sensitivity • Individual person sensitivity

  23. Risk From Exposure • No observed increase of risk at occupational exposures • Risk factor: 4 x 10- 4 latent health effects per rem (LNT model) • Cancer formation latency time > 10 yr • More solid tumor formation at old age

  24. Health Risks 20 cigarettes/day 6 years 15% overweight 2 years Consuming alcohol 1 year All Accidents 1 year Motor vehicle 207 days Home accident 74 days Drowning 24 days Natural hazards 7 days Medical radiation 15 days 620 mrem/y for 47 y 31 days (US Background dose) 1 rem/y for 47 y 50 days Industrial Accidents All industries 60 days Agriculture 320 days Construction 227 days Mining 167 days Transportation 160 days Government 60 days Manufacturing 40 days Trade 27 days Services 27 days Nuclear Plant 27 days Perspective of RiskEstimated Loss of Life Expectancy during lifetime

  25. DOE & USNRC Occupational Dose Limits Whole Body 5 rem per yr Lens of Eyes 15 rem per yr Extremities 50 rem per yr Skin 50 rem per yr Organ or Tissue 50 rem per yr Unborn Child 0.5 rem pregnancy (US Background 0.62 rem per yr)

  26. Declared Pregnant Worker(Embryo / Fetus) • Policy: Female radiation worker encouraged to voluntarily notify supervisor (written) if pregnant. • Employer must provide agreeable work with limited (~no rad) exposure @ no loss of pay or promotional opportunity • Further occupational rad exposure unlikely during pregnancy.

  27. Occupational Dose Equivalent Limits • General Public 100 mrem/yr • Any Occupational Worker (unmonitored) 100 mrem/yr • Radiation Worker (monitored) 5,000 mrem/yr = 5 rem/yr

  28. External & Internal Radiation Dose Reduction • Use shielding if possible • Minimize time in radiation field • Maximize distance to rad source • Dose ~ Source x time / (distance)2

  29. ALARA • As Low As Reasonably Achievable (called ALARA by regulators) Radiation protection program manage exposures (individual & collective to workforce & public) as low as social, technical, economic, practical, public policy permit. ALARA not dose limit but a process “maintain dose levels “As Low As Reasonably Achievable.”

  30. ALARA Management Policy Radiation exposure maintained As Low As Reasonably Achievable, considers social & economic needs. Radiation exposure to workers controlled to ensure radiation exposures well below regulatory limits. No occupational radiation exposure allowed without expected benefits (health, economic, social, etc.).

  31. Radiological Control Responsibilities • Provide technical & programmatic control over radiation & radioactive materials • Provide Health Physics (HP) personnel & monitoring equipment • Issue Radiation Work Permits (RWPs) • Maintain dosimetry program • Maintain training program

  32. Radiation Posting Requirements • Areas controlled for radiological purposes designated with magenta (or black) standard three-bladed radiological warning symbol on yellow background • Yellow & magenta ropes, tapes, chains, or other barriers used to denote & control boundaries.

  33. Radiological Areas • Radiological Buffer Area • Radiation Area • High Radiation Area • Very High Radiation Area • Contamination Area • High Contamination Area • Fixed Contamination Area • Soil Contamination Area • Airborne Radioactivity Area

  34. Area with radiation dose rates > 5 mrem/hr but < 100 mrem/hr Entry requirements: Rad Worker I or II Training Worker signature on RWP Required Dosimetry Requirements in work area Don’t loiter Practice ALARA Radiation Area

  35. Radiation dose rate > 100 mrem/hr & < 500 rad/hr. Entry requirements Radiological Worker II Training Worker’s signature on job-specific RWP Requirements for work in area Personnel & supplemental dosimeters Survey meters or dose rate indicating device Access points secured by control devices, locks, etc. High Radiation Area

  36. Area where radiation dose rates > 500 rad/hr Entry requirements: Radiological Worker II Training Worker signs job-specific RWP Requirements for work in area: Personnel & supplemental dosimeters Survey meters or dose rate indicating device Access points secured by control devices, locks, etc. Very High Radiation Area

  37. Contamination Area Area where surface has removable contamination > given limits Entry Requirements: Radiological Training II Worker signs RWP Requirements for work in area: Personnel dosimeter if necessary Minimize dust generation Respiratory protection if necessary

  38. High Contamination Area Area where surface has removable contamination >10 times limits. Entry Requirements: Radiological Training II Worker signs RWP Requirements for work in area: Personnel dosimeter if necessary Minimize dust generation Respiratory protection if necessary

  39. Soil Contamination Area Area where surface soil contaminated above limits Entry Requirements: Radiological Training II Worker signs RWP Requirements for work in area: Personnel dosimeter if necessary Minimize dust generation Minimize earth disturbance Respiratory protection if necessary

  40. Airborne Contamination Area Area where surface soil contaminated above limits. Entry Requirements: Radiological Training II Worker signs RWP Requirements for work in area: Personnel dosimeter if needed Minimize dust generation Minimize earth disturbance Respiratory protection

  41. Requirements for Exiting • Exit at step-off pad provides “barrier” between contaminated & clean areas to prevent spread of contamination. Remove protective clothing • Perform whole body survey. If contaminated: stay in area, notify Radiological Control personnel, minimize cross-contamination. • After exiting & monitoring self, wash hands before eating, drinking, chewing, applying make-up, etc.

  42. Entry requirements into Rad Materials Area if whole body dose rate > 5 mrem/hour or contamination > specified limits Same for entry into Radiation Area or Contamination Area Depends on radiological hazard present. Radioactive Material Area

  43. Hot Spot Identification • Hot spots - Source of radiation or rad material in area, equipment or piping • Rad levels at such spots typically higher than surrounding area • Avoid hot spots if possible

  44. Stop or secure spill source Warn others in area Isolate spill if possible Minimize exposure & contamination Secure unfiltered ventilation Requirements for exiting - Site specific monitoring - Monitor per posted instructions before entry to clean area Notify Rad Control personnel Changing rad conditions. Actions don’t create rad problems for others. Be alert for activities that change rad conditions Control of Radioactive Spills

  45. Radiation Work Permits • Rad Work Permit used to control routine or repetitive activities such as inspections in areas with stable radiological conditions. Valid for up to one calendar year. • Job-Specific Radiation Work Permit control non-routine operations in areas with changing radiological conditions. Valid only for duration of job.

  46. Emergency Dose Limits • Protecting property if 5 rem not practical • 10 rem • Lifesaving or protection of small population if dose limit not practical: • 25 rem • Lifesaving or protection of large population (volunteer basis for person aware of risk) • > 25 rem

  47. Place rad waste only in Rad Waste receptacles Don’t put non-rad waste or reusable rad material in Rad Waste containers Segregate compactable material from non-compactable material Minimize mixed waste generation Use good housekeeping techniques Segregation Rad Materials

  48. Personnel Protective Clothing • Protective Clothing used to enter areas with rad levels above specified limits to prevent skin contamination • Clothing depends on work area, rad conditions, job, etc. • Full protective clothing includes coveralls cotton glove liners & gloves hood shoe covers & rubber overshoes.

  49. Decontamination • Decontamination - removal of rad materials from locations not wanted • Personnel decon usually done using mild soap & lukewarm water. • Material decon- removal of radioactive material from tools, equipment, floors & other surfaces

  50. - Thank you for your participation - Community Environmental Monitoring Program CEMP END of Training ANY QUESTIONS?

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