Dosimetry

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Dosimetry
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Dosimetry

• External
• Necessary for high energy betas, gammas, X-rays,
  neutrons.
• Pocket dosimeters
• Film badges
• TLDs

• Internal
• Necessary for low energy betas and alphas
• Air monitoring
• Urine bioassay

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External dosimetry
Pocket dosimeters. Used when entering radiation
fields. These are personal monitors, but dont
record any exposure level. The wearer must
monitor and report exposures. Can be purchased
with a variety of sensitivities..ranging from
0-200 mR up to 600 R.
Modern electronic dosimeters
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External Dosimetry
Film Badges
Not user readable. Must be analyzed by a
licensed lab. Provides cumulative exposure over
longer periods.
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Film Badges
X-ray film (in light tight packet)
Open window for determining beta exposure
Windows with filters of increasing gamma
absorbancy, to determine the energetics of gammas
or x-rays
After exposure (or after a specific time period,
the film is developed and compared to standards.
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Dosimetry Report
This period YTD Lifetime
Deep Eye Shallow
Type of badge
Monitoring period
lt 10 mR
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Thermoluminescence Detectors

• Look like a film badge
• Takes advantage of electron excitation due to
  radiation interaction with a crystal material
  (often LiF). Electrons are trapped in a
  metastable state.
• When heated, the electrons are driven back to the
  ground state releasing light.

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Reading TLDs

• Works for high energy betas, gammas, and x-rays.
• Best ones can determine multiple ranges of dose.

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Internal Dosimetry

• Indirect
• Measure potential intake via air inhalation or
  ingestion pathways
• Model exposure based on uptake fraction,
  biological and physical halflives.

• Direct
• Bioassay. Collection of excreta and measurement
  of radioactivity.
• Model uptake based on excretion models.

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Air Monitoring

• Always done for procedures involving potential
  for dust, aeresol, or volatilization exists
• Requires Pump, filters, mechanism to measure
  deposited radioactivity

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Personal air monitoring

• Breathing Zone
• Portable pump
• Small (1.5) filter
• Keep filter near face if possible.

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Area Monitoring

• Larger pumps
• May be extended monitoring.
• Can also use passive monitoring (e.g. radon
  canisters)
• Can be extended to very large areas

Large scale air monitor for chernobyl Pump pulls
120L/min
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Air Monitoring

• Derived air concentration (DAC)
• Annual Limit of Intake (ALI)
• DAC is the concentration of a radionuclide, that
  if inhaled for a period of one year results in
  one times the ALI
• ALI - The derived limit for the amount of
  radioactive material taken into the body of an
  adult worker by inhalation or ingestion in a
  year. ALI is the smaller value of intake of a
  given radionuclide in a year by the reference man
  that would result in a committed effective dose
  equivalent of 5 rems (0.05 sievert) or a
  committed dose equivalent of 50 rems (0.5
  sievert) to any individual organ or tissue. (see
  10 CFR 20.1003.)

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In other words

• The NRC has determined the amount of intake by
  inhalation or ingestion of each specific
  radionuclide that would give a dose of 5 rem
  (whole body) or 50 rem to an organ. This is the
  ALI.
• If you breath air for 2000 hours over the course
  of a year that is contaminated with enough
  concentration of a particular radionuclide to
  give you a 5 rem dose you have taken in one DAC.

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10 CFR 20 Appendix B
Hydrogen-3
AtomicNo. Radionuclide Class Table 1Occupational Values Table 1Occupational Values Table 1Occupational Values Table 2Effluent Concentrations Table 2Effluent Concentrations Table 3Releases toSewers
AtomicNo. Radionuclide Class Col. 1 Col. 2 Col. 3 Col. 1 Col. 2 Table 3Releases toSewers
AtomicNo. Radionuclide Class OralIngestionALI(µCi) Inhalation Inhalation Air(µCi/ml) Water(µCi/ml) MonthlyAverageConcentration(µCi/ml)
AtomicNo. Radionuclide Class OralIngestionALI(µCi) ALI(µCi) DAC(µCi/ml) Air(µCi/ml) Water(µCi/ml) MonthlyAverageConcentration(µCi/ml)
1 Hydrogen-3 Water, DAC includes skinabsorption 8E4 8E4 2E-5 1E-7 1E-3 1E-2
1 Hydrogen-3 Gas (HT or T2) Submersion1 Use above values as HT and T2 oxidize in air and in the body to HTO Gas (HT or T2) Submersion1 Use above values as HT and T2 oxidize in air and in the body to HTO Gas (HT or T2) Submersion1 Use above values as HT and T2 oxidize in air and in the body to HTO Gas (HT or T2) Submersion1 Use above values as HT and T2 oxidize in air and in the body to HTO Gas (HT or T2) Submersion1 Use above values as HT and T2 oxidize in air and in the body to HTO Gas (HT or T2) Submersion1 Use above values as HT and T2 oxidize in air and in the body to HTO Gas (HT or T2) Submersion1 Use above values as HT and T2 oxidize in air and in the body to HTO
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10 CFR 20 Appendix B
Americium-241
AtomicNo. Radionuclide Class Table 1Occupational Values Table 1Occupational Values Table 1Occupational Values Table 2Effluent Concentrations Table 2Effluent Concentrations Table 3Releases toSewers
AtomicNo. Radionuclide Class Col. 1 Col. 2 Col. 3 Col. 1 Col. 2 Table 3Releases toSewers
AtomicNo. Radionuclide Class OralIngestionALI(µCi) Inhalation Inhalation Air(µCi/ml) Water(µCi/ml) MonthlyAverageConcentration(µCi/ml)
AtomicNo. Radionuclide Class OralIngestionALI(µCi) ALI(µCi) DAC(µCi/ml) Air(µCi/ml) Water(µCi/ml) MonthlyAverageConcentration(µCi/ml)
95 Americium-241 W, all compounds 8E-1Bone surf 6E-3Bone surf 3E-12 - - -
95 Americium-241 W, all compounds (1E0) (1E-2) - 2E-14 2E-8 2E-7
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Air sample report
Occupational or Non-occupational DAC value________ ?Ci/ml Radionuclide _____________________ Site ____________Location _________________Sampled By _______________________________ Monitored Workers Instrument Model Serial No. Calibration Due Date Date/Start Time / Flow Rate Date/Stop Time / Flow Rate Date/Start Time / Flow Rate Date/Stop Time / Flow Rate Sample Volume (lpm) ? (minutes) Liters (A) Counter _________________ Number Cal. Due Count Date ___________________Count Start Time___________ Count Stop Time
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ALPHA Sample counts _________counts Sample count rate CPM Background count rate CPM Net count rate __________CPM (B) Counter efficiency (C) Collection efficiency (D) Efficiency (C)x(D) (E) Activity (B)/(E) (F) Conc. (F) / (2.22 E 9 X A) _________(G) DAC (G) / (6E-12) BETA Sample counts _________counts Sample count rate CPM Background count rate CPM Net count rate __________CPM (B) Counter efficiency (C) Collection efficiency (D) Efficiency (C)x(D) (E) Activity (B)/(E) (F) Conc. (F) / (2.22 E 9 X A) _________(G) DAC (G) / (6E-12) __________