slide 1 atomic structure & radiation gary m. sandquist, phd, chp, pe 2011 training session...
TRANSCRIPT
Slide 1
Atomic Structure & Radiation
Gary M. Sandquist, PhD, CHP, PE
2011 Training Session
Community Environmental Monitoring Program CEMP
Slide 2
CEMP Training OutlineCEMP Training Outline
Basic Atomic Structure Introduction to Radioactivity Radiation Sources Biological Effects Radiation Risks Radiation Limits
Slide 3
CEMP Training OutlineCEMP Training Outline
Personnel Monitoring ALARA Program Radiation Posting & Control Radiation Work Permits Radiological Emergencies
Slide 4
CEMP Training OutlineCEMP Training Outline
Radioactive Waste Minimization
Radiation Contamination Control
Practical Exercise
Slide 5
IsotopesIsotopes
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
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Stable & Unstable AtomsStable & 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.
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Alpha Particles ( He4 )Alpha Particles ( He4 )
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 airor one sheet of paper.
BIOLOGICAL HAZARD No external
radiation hazard. Internally deposits large
amount of energy in small volume of body
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Beta Particles ( e-1 or e+1 )Beta Particles ( e-1 or e+1 )
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.
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Gamma/X Rays (or x )Gamma/X Rays (or x )
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.
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Activity UnitsDisintegrations Per Unit Time
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
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Radiation Dose UnitsRadiation 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
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Radioactive Half-lifeRadioactive 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)
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Natural Sources (2006 NCRP)Natural Sources (2006 NCRP)
Cosmic radiation ~ 5% Terrestrial radiation ~ 3% Internal radiation ~ 5% Radon / Thoron ~ 37 %
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Man-Made SourcesMan-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
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Medical RadiationMedical 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
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620 mremTotal average US
rad exposure(NCRP report 160 - 2006)
Prior US level - 360mrem
Average Total Annual DoseAverage Total Annual Dose
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Radiation DamageRadiation 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
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Possible Effects on CellsPossible Effects on Cells
No damage evident
Damage repaired & cell normal
Damage not repaired & cell functions abnormally
Cell dies
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Cell SensitivityCell 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 )
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Dose Rate EffectsDose 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
Slide 22
Factors for Biological DamageFactors 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
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Risk From ExposureRisk 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
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Perspective of RiskEstimated Loss of Life Expectancy during lifetime
Perspective of RiskEstimated Loss of Life Expectancy during lifetime
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
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DOE & USNRC Occupational Dose Limits
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)
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Declared Pregnant Worker(Embryo / Fetus)
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.
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Occupational Dose Equivalent Limits
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
Slide 28
External & Internal Radiation Dose Reduction
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
Slide 29
ALARAALARA
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.”
Slide 30
ALARA Management PolicyALARA 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.).
Slide 31
Radiological Control Responsibilities
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
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Radiation Posting RequirementsRadiation 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.
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Radiological AreasRadiological 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
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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 AreaRadiation Area
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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 AreaHigh Radiation Area
Slide 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 AreaVery High Radiation Area
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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
Contamination AreaContamination Area
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Area where surface has removable contamination >10 times limits.Entry Requirements:Radiological Training IIWorker signs RWPRequirements for work in area:Personnel dosimeter if necessaryMinimize dust generationRespiratory protection if necessary
High Contamination AreaHigh Contamination Area
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Area where surface soil contaminated above limits
Entry Requirements:Radiological Training IIWorker signs RWP
Requirements for work in area:Personnel dosimeter if necessaryMinimize dust generationMinimize earth disturbanceRespiratory protection if necessary
Soil Contamination Area Soil Contamination Area
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Area where surface soil contaminated above limits.Entry Requirements:Radiological Training IIWorker signs RWPRequirements for work in area:Personnel dosimeter if neededMinimize dust generationMinimize earth disturbanceRespiratory protection
Airborne Contamination Area Airborne Contamination Area
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Requirements for ExitingRequirements 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.
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Radioactive Material AreaRadioactive Material Area
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.
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Hot Spot IdentificationHot 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
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Control of Radioactive SpillsControl of Radioactive Spills
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
Slide 45
Radiation Work PermitsRadiation 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.
Slide 46
Emergency Dose LimitsEmergency 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
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Segregation Rad MaterialsSegregation Rad Materials
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
Slide 48
Personnel Protective ClothingPersonnel 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.
Slide 49
DecontaminationDecontamination
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