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Have the same Z (protons)
have the same A (atomic mass)
have the same neutrons
Electron volt (eV)
Kinetic energy acquired by an electron accelerated through potential difference of 1 volt
Electron charge (e)
- Quantity of charge possessed by electron
- e= 1.602x10-19 coulombs
wave theory and value or c
- c=speed of light in a vacuum
- 3E+8 m/sec
particle theory and value for h
- h=6.626e-34 Planck's constant
Energy in Joules
what is 1eV in joules
where does X-rays come from?
where does gamma rays come from?
What are the characteristics of neutron radiation?
- Have high energy (several Mev)
- Long range due to lack of charge
- High H content materials for shielding
- Internal and external hazard.
- can make something radioactive
Discovered uranium to be weakly radioactive?
what is Stopping power S
- average linear energy lost by a charged particle per unit distance of travel
- depends on:
- particle energy
- absorber z
- absorber density
These have high LET
alpha and neutrons
these have low LET
beta, gamma, X-rays
Which beta undergoes annihilation? produces 2 .511 Mev photons at 180 degrees
Unit for density of thickness of material
Fast/ high energy neutrons are:
Slow /thermal or low energy neutrons
Coherent scattering photon energy
<= 15-30 keV around 10kev
Compton effect is higher for.
for hydrogen (water)
Pair production threshold energy
Triplet production threshold energy
Photodisintegration threshold photon energy
Equation to look for the number of radioactive atoms?
1R = in C/Kg
2.58 E-4 C/Kg
Estimation of gamma exposure
- C=activity in CI
- Distance in FEET
Exposure rate using gamma constant
distance in CM
ICRP exposure standard for SKIN
ICRP exposure standard for EXTREMITIES
ICRP exposure standard for MINORS
10% OF ANNUAL LIMITS
ICRP exposure standard for EMBRYO/FETUS
500 MREM IN GESTATION PERIOD
ICRP exposure standard for GENERAL PUBLIC
Gas Filled Detector Curve 6 regions
- 1-Recombination region
- 2-Ionization region
- 3-Proportional region
- 4-Limited Proportional region
- 5-Geiger-Mueller region
- 6-Continuous Discharge region
Radiation in a mammogram exam?
What is the Annual Limit on Intake?
What is the assumed radiation risk for workers?
- .04 Sv-1 for fatal cancer
- .008 Sv-1 for non fatal cancer and severe genetic effects
what is the assume radiation risk for members of the public?
- .05 Sv-1 for fatal cancer
- .01 Sv-1 for non fatal cancer
- .013 Sv-1 for severe genetic effects
what are the public dose limits?
1mSv /year based on stochastic effects
- 15 mSv/year to lens of the eye
- 50 mSv/year to skin, hands, and feet
- 2 mSv to the women's abdomen once pregnancy has been declared.
- Based on deterministic effects
What is the total average annual population exposure worldwide due to low LET radiation?
Recombination Region low applied voltage
Ionization chamber region increase applied voltage
Advantages of Ion chambers
- -can measure low exposures (microR/hr)(natural background)
- -Reasonably flat energy response
- -Good for beta, gamma, and x-rays
- -No dead time concerns
Ion chambers Disadvantages
- -sensitivity depends on volume
- -can be slow, erratic
- -non-unifor exposure leads to under estimate of dose
- -environmental effects
Proportional region 3 applied voltage further increases:
Advantages of proportional counters
- -measure energies of incident radiations
- -useful in mixed fields
Disadvantages proportional counters
- dead time (0.5 to 10 micro se)
- voltage fluctuations
- requires gas supply
- heavy and expensive
Region of limited proportionality as applied voltage increases:
gas multiplication factor changes.
Geiger-Muller region treshhold voltage:
Advantages of GM counters
- -High sensitivity
- -fast response time
- -simple design, low cost
Disadvantages of GM counters
- -Low dead time (100 to 300 micros)
- -strong energy dependence (over responds at low energies)
Voltages above GM region are not used
what is scintillation?
absorption of photon energy by substance and re-emission as visible light
Photoluminescence <10^-8 sec
- Phosphorescence (delayed)
- ei TL and OSL
3 types of scintillation detectors
- Solid scintillaiton
- Portable counters
- Liquid scintillation
Advantages of solid scintillation
- high sensitivity for gamma
- high efficiency
Disadvantages of solid scintillation
expensive and fragile
advantages of portable counters
- high sensitivity for beta and gamma
- flat energy response if tissue equivalent (mcrorem meter)
disadvantages of portable counters
advantages for liquid scintillation
- high sensitivity for beta
- best method for low energy beta
disadvantages for liquid scintillation
- quenching (LSC)
- liquid waste
semiconductor detectors create:
- a charge "depleted zone" at junction
- -zone is sensitive volume
- -sensitivity depends on depleted zone size
- -size of zone depends on applied voltages
collection of ions lead to this
What are the advantages of semiconductors detectors?
- energy resolution
- can be used for particles by making N layer very thin (2 atoms)
- -smaller depleted zone, but sufficient to stop particle
- -alpha spectroscopy
Disadvantages of semiconductors detectors?
detectors must be cooled to very low ten (liquid nitrogen) (-196 C or 410 F)
formula to calculate detector efficiency
What are the advantages of digital pocket ion chamber?
- -small, compact
- -reasonably sensitive and accurate
- -immediate readout
- -store exposure record to extended period of time
- -data download for storage
What are the disadvantages of a digital pocket ion chamber?
- -limited exposure range
- -no permanent, legal record
what is Doubling Dose?
Radiation dose, if delivered to large population, would double the number of spontaneous mutation.
What is the estimated ICRP human doubling dose?
- Increase risk of lung cancer demonstrated.
- Atributed to radon and daughters exposure
What is WLM working level month
Unit of radon decay product exposure
Rule of thumb: 1 WL about 120 pCi/L radon concentration
No lung cancer <120 WLM; highest risk 120 to 600 WLM--Today: 1 to 2 WLM/yr (5 lung cancer death/106 person-yr/WLM)
How many days biological half life for Class D?
< 10 days biological half life
How many days of biological half life for Class W?
10 to 100 days biological half-life
What is workload (W)
the amount of time the X-ray unit is in operations. number of exams at a given technique. Averaged over a year if possible
what is 1 R in rad (tissue)
what is 1 R in rad (air)
what is T?
Occupancy factor: fraction of the beam on time that a shielded area is occupied by a given individual.
What are the three sources of radiation?
Primary, leakage, and scatter
what is shielding task?
barrier is acceptable if it decreases the radiation dose behind the barrier to P/T
How is Workload specified? (W)
mA*min per week
How many days of biological half life for Class Y?
>100 days biological half life
what is the average annual exposures worldwide to natural radiation sources (high and low LET)?
Leakage for xray tube housing shouldn't be more than:
How far must patients be from collimator?
15 cm for skin sparing
what is PBL?
Positive beam imitation are electronic sensors in image receptors that adjust collimtors so the xray beam is no larger thanimage receptor.
how much is inherent filtration?
.5mm of Al equivalent
what is total filtration?
2.5 mm. and it's checked annually
For equipment design, what do we want exposure reproducibility to be?
Variability of 5% or less
what do we want exposure linearity to be?
less than 10%
what reduces pt dose in film screen?
- use of intensifying screenings
- faster screen film systems
- higher KVP
when do you use grids?
body parts of >10cm
increase dose but improves contrast
relationship of airgap technique and dose?
it doesn't eliminate increase in dose
what should SSD source to skin distance must be to reduce effects of inverse square fall of
Advantages of image intensifier in fluoro
- -increased image brightness
- -saves time for radiologist
- -requires lower mA so lower dose
what is the exposure rate limit at table top with image intensifier 12" above it.
what is the exposure rate limit with high level control or boost mode?
what should SSD be for fixed and mobile fluoroscopy?
- fixed=no less than 15cm
- mobile=no less than 12cm
what are the advantages of minimzing OID in fluoro?
- -reduces magnification
- -reduces unsharpness (blur)
- -allows image intensifier to intercep more scatter
- -decrease occupational exposure
what are the repercussions of using large OID?
- -small SSD
- -increased magnification
- -more geometric blur
- -more occupational exposure
how thick should lead apron be?
.25 mmPb equivalent
if bucky and spot film curtain are not used, exposure can be more than?
100mR/hr at 2 feet from side of table
what is the exposure at 1ft of the table with no arm drape?
Characteristics of a controlled space?
- -occupational exposure
- -Individuals monitored
- -limitation 100 mrem/week max
characteristics of uncontrolled spaced?
- -incidental public exposure
- -individuals not monitored
- -limitation is 2 mrem/week maximum
what is the conversion of R to Rad?
- 1 R=.87 Rad in air
- 1 R=.97 Rad in tissue
The sum of the weighted equivalent for all irradiated tissues or organs
- Effective Dose
- E=sum Wt X HT
How much time the x-ray unit is in operation?
What is the fraction of the beam-on time that a shielded area is occupied by a given individual?
What is the shielding task?
barrier is acceptable if it decreases the radiation dose behind the barrier to P/T
what are the assumed conservative distances?
- .3 meters out
- .5 meters up
- 1.7 meters from floor below up
what are the 3 sources of radiation?
- primariy rad=useful beam
- second rad=scatter+leakage
How high do we shield walls?
Lead dimensions for Radiographic and CT rooms.
- radi and fluo=1/32" and 1/16"
- bone density and mammo=none
how bad was the
contamination of radioactive waste discharged to the Techa River?
what is RDD
- Radiological Dispersal Device
- to spread radioactive material through a detonation of conventional explosives
- or other nonexplosive mean
- ei. po-210 poisoned ex KGB agent
what is SRD?
- Simple Radiological
- Causing radiological exposrue without an explosion.
waste contaminated iwth or containing radioisotopes
- 100 mnograms per gm of alpha emittng radioisotopes
- beyond uranium on periodic table. t1/2 20yrs
high level radioactive waste
hily radioactive; fission products (spent fuel)
Low Level Radioactive waste
- (low activity/high vol)
- not high level or transuranic waste
Uranium Mill tailings
from the mining and milling of uranium ore
- naturally occuring rad material
- not regulated by NRC
- NORM or Accelerator-produced Radioactive material
- not regul by NRC
- Radioactive and hazardous
- Due to chemical or biological materials
class A waste classification
- -usually segregated wastes
- -lowest isotope concentration
-95% LLRW is clas "A
Packagin reqs for class A
- - <1% reestanding liquid,
- -carbard/fibergboard boxes unnaceptable,
- -non-explosive, not biological and non-ppyrophoric
Class B waste class
- -intermediate isotope concentration
- -special stability reqs
- Must be able to maintain its physical form
- -Container structural reqs
Class C waste
- -Highest allowable isotope conce
- -Meet reqs of class B
- -Special precautions to protect against HUMAN INTRUSION
Current US radioactive waste disposal sites are in?
- Handford WA
- Evirocare in Clive UT
- New in Texas
What is Waste Isolation Pilot Plant (WIPP)
World's first underground repository licensed to safely and permanently disposed of transuranic waste from research and production of nuclear weapons
wasted stored in salt mine 2150 feet underground near Carlsbad NM
DOE site for highly radioactive spent fuel from nuclear power plants and high level waset from weapons program
- Located in Nevada
- was supposed to open in March 2017
NRC Lessons learned after Fukosh
- -Mitigation strategies to respond to extreme natural events resulting in the loss of power and plants
- -Ensuring reliable hardened containment vents
- -Enhancing spent fuel pool instrumentation
Major radionuclines of concern in Chernobyl accident
Cs-137 and I-131
ARS and associated fatalities did not occur among the general poplation of
Radioactive Waste discharged to the Techa River when?
- early 1950-1960
- 2.75 Mci discharged
- Could not use as drinking water source...ban ignored
- External radiation was up to 120 times bkgd
What happened in Kyshtym accident?
- stem explosion 29sep 1957
- 200 died of radiation sickness in years following accident
- Slow evaquation, increase dose
what happened in Karachay Lake incident
- 120 MCi discharged beggining 1951-53
- Low precipitaion allowed lake level to recede.
- Contamination was 3-9mrem/year
- They are concerned wih drinking water
Which are the two bomb accidents?
- Mars Bluff, SC march 11 1958
- -B-47 accidently released bomb, several injured
- GOldsboro, NC janu 24 1961
- -B-52 caught fire, exploded. 3 crew killed.
- -2 bombs released.
- bomb 1-4 out 4 arming devices activated
- bomb 2-plunged into a muddy field.
Effects of Normal explosive?
- 500-2000 lbs TNT
- Blast (100%)
Effects of Nuclear Detonation?
- Blast 50%
- Thermal Energy 35%
- Radioactive 14%
- Electromagnetic pulse 1%
- Economic and social disruption
- Environmental damage
what is RDD?
- Radiological Dispersal Device
- Designed to spread radioactive material through a detonation of conventional explosives or other non explosive materials
can be silent inteded to spread in food or water. ei Po-210 poisoning of agent
RDD possible outcomes?
- -contamination of people and environment
- can deny the use of facilities and areas
- will most probably have significant economic impact
- may hamper emergency response efforts and can delay hospital treatment
- -material and weather dependent
What happens with the use of RDD?
- Explosion spreads radioactive material (contamination)
- Nuclear detonation does NOT occur
Extreme Caution Radiation Boundary:
High Radiation Boundary:
Medium Radiation Boundary?
Low radiation boundary?
Incident in Goiania Brazil?
CS-137 was rubrued expsing 250 people, killing 4. Dose ranged 50-300
What is Simple Radiological Device (SRD)?
- Causing radiological exposure without an explosion.
- Ex. P-32 in the water cooler at NIH, lunch at MIT
- I-125 in food at Brown university
Radiation Area Caution sign means?
Rad levels could result in an individual receiving a dose equivalent in excess of .005 rem in one hour at 30 cm from rad source
What does High Radiation Area Caution sign mean?
dose equiv could result in excess of 0.1 in one hour at 30 centimeters
What does Very High Radiation Area mean?
dose of 500 rads in one hour at 1 meter from radiation surface
Examples of Engineering Controls
- Fume hoods
- Glove boxes
- ventilation systems
- vacuum systems
- hot cells
- shielding rooms
- interlocks, mazes, "fail-safe"
Examples of PPE
- Lead lined gloves
- lead lab coats
- Cover alls
- Shoe covers or boots
- HEad covers
- -Containment: primary and secondary, engineering controls
- -Spill control
- -Liquid transfer techniques
- -handling precautions
- -protective clothing
- -licensing and permits
- -stay times
- -Radiation surveys
- -Leak tests and shutter tests
- -Enforcement options
Leaking source legal limit?
12 Commandments of radiation safety
- source shielding
- source reduction
- personal barrier
- contamination control
- effect mitigation
- optimal technology
- limit other expsures
First clinical sign of Chronic Radiation Syndrome
- -reduction in blood leukocytes
- -reduction in platelet counts
- -bone marrow hypoplasia
- -Leucopenia is generally associated with a reduced number of granulocytes
- -Lymphocyte counts is less affected' but at high doses >4Gy usually lead to pronounced persistent leucopenia
Haematopoietic changes accompanied by:
- changes in immune, nervous, cardiovascular, muscoloskeletal systems and in the GI tract
- -High doses 4.5Gy-Encephalomyelitis-type changes
- -Reduced resistance to infection
- Dysfunction in othe organs
- -Reduced secretary funtion of the gastric mucosa, mild thyroid dysfunction,
What is the approx background radiation in the US?
- Gamma, Xray, beta, Hw=1
- Thermal Neutrons=2
- Fast Neutrons, Protons=10
What is CEDE?
- Committed Effective Dose Eq
- Represents radiation risk from internal radioactivity that is equivalent in risk to uniform whole body external exposure of the same numerical number
What is TEDE (Total Effective Dose Equivalent):
Sum of external deep-dose equivalent and internal dose equivalent (CEDE)
Summation is not required if estimated dose is less than 10% of he annual dose
Internal Dose classes:
- Class D:
- < 10 days biological half-life
- Class W
- 10-100 days biological hal-life
- Class Y
- >100 days biological half-life
Problems with cancer risk models:
- -cancers are indistinguishable
- -Long latency period
- -Cannot perform human experiments
- -Studies may suggest radiation as the cause of cancer but
- *33% natural backgorund risk
- Multiple causes of cancer
Effective dose in a chest xray
Early Effects to Skin, Blood, and Thyroid dysfunction. DETERMNISTIC
- Erythema-200-500 rads
- Epilation 400 rads
- Ulceration >1000 rads
- Lymphocite decrease 25-30 rads
- Thyroid dysfunction 30 rem
Classic symptoms of high doses?
- -possibly diarrhea depending on dose.
Acute Effects with Dose:
- Hematopoietic Syndrome-2-5 Gy
- GI Syndrome-5-12 Gy
- Cerebrovascular Syndrome-100 Gy
Vomiting with ARS begins with doses of:
- 6-8 Gray
- Delay time of 1 hour
chance of developing cancer from a 1 rem whole body dose?
Skin Cancer and Leukemia common in:
early xray workers, physicists and engineers
Lung cancer common in:
- -pichblende miners in Saxony
- -Uranium miners
Bone tumors common in:
- -Radium Dial workers
- -20s and 30s radium treast ments for TB and Ankylosing Spondilitis
3 types of chromosonal abberrations lethal to cell:
- Centric Ring
- Anaphase Bridge
2 Important Non-lethal chro rearrangements:
- Symmetric Translocations
- Deletions(Interstitial and Terminal)
Radiosensitivity of Lymphocytes:
- Single most sensitive cell
- Threshold about 25 rem
- Few hundred rem results in sever drop in circulating lymphocyte count within hours
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