Miscellaneous Instruments For Field Use

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Miscellaneous Instruments For Field Use

• Cember, Ch 9 and elsewhere

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CDV-700

• Geiger Mueller
• High range
• Not allowed in state of Oregon
• Not RF shielded
• Responds in RF field (2 incidents )
• State banned their use

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CDV-700Pre-Operational Check

• Perform AWAY from suspected radiation
• Install batteries
• Turn selector switch to X10 allow 30 seconds
• Rotate beta shield FULLY OPEN, place open window
  of probe in contact with check source. Meter
  should move to about the middle of the scale.
• Switch instrument off when not in use.

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CDV-715 high range ion chamber
DO NOT USE!
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Victoreen 190

• Dose Rate Monitoring
• Energy compensated gm

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Victoreen 190 Pre-Operational Check Dose Rate
Monitoring

• Perform AWAY from suspected radiation
• Attach probe and tighten screw
• Push on/off button and observe screen
• Verify scale indication is micro-roentgen per hr
  (?R/hr)
• Note If you are not in a low background area,
  it may read higher (mR/hr)
• Leave audio off
• Open probe. Place open area close to the check
  source. The instrument should read about 700
  ?R/hr. If it doesnt, DO NOT USE THIS
  INSTURMENT!
• Close the probe

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Victoreen 190

• Contamination Monitoring
• Pancake proble

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Victoreen 190 Pre-Operational Check Contamination
Monitoring
CAUTION! Delicate end window

• Perform AWAY from suspected radiation
• Attach probe and tighten screw
• Push on/off button and observe screen
• Verify scale indication is in counts per minute
  (C/min). If not, push the mode button to switch
  scales.
• Turn audio on
• Place open area close to the check source. The
  instrument should read about 5000 C/min. If it
  doesnt, DO NOT USE THIS INSTURMENT!

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Victoreen 190

• Alpha Contamination Monitoring
• Zn scintillator

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Victoreen 190 Pre-Operational Check Alpha
Contamination Monitoring
CAUTION! VERY delicate end window

• Perform AWAY from suspected radiation
• Attach probe and tighten screw
• Push on/off button and observe screen
• Verify scale indication is in counts per minute
  (C/min).
• Turn audio on
• Place open area close to the check source. The
  instrument should read about 500 C/min. If it
  doesnt, DO NOT USE THIS INSTURMENT!

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Pocket Dosimeters and Pocket Chambers

• Personal radiation monitoring devices

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Pocket Dosimeters and Pocket Chambers

• Small ionization chambers
• Usually worn in the pocket.
• Designed to measure x-rays and gamma ray
  exposures
• Also respond to betas above 1 MeV.
• Neutron-sensitive versions were also available.
• Pocket chamber and pocket dosimeter are often
  used interchangeably.
• Original distinction of terms is rarely made
  anymore.
• Due to fact that pocket chambers are rarely used
  any more.

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Pocket Dosimeter (one form)
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Pocket Dosimeters

• Known by other names
• direct-reading dosimeters,
• self-reading pocket dosimeters
• pocket electroscopes
• Quartz fiber electroscopes
• sensing element is a movable bow-shaped quartz
  fiber
• attached at each end to a fixed post.
• looking through eyepiece, pointing other end
  towards a light source, and note position of
  fiber on a scale

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Pocket Chamber
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Pocket Chambers

• Also known as
• indirect-reading dosimeters, non-self-reading
  dosimeters and
• condenser-type pocket dosimeters
• PC acts as an air-filled condenser (capacitor)
• Given a charge prior to use with a charger-reader
• Any subsequent exposure to radiation
• ionizes the air inside the chamber
• reduces the stored charge.
• Exposure is quantified by measuring the decrease
  charged and relating to exposure

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CDV-750 Charger
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CDV-138 Dosimeters
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Charging Civil Defense Dosimeters

• Insert one D cell battery in the CDV-750 charger
• Place the dosimeter on the charging pin.
• Using the knob, adjust the hairline until it is
  between 0 and 10 mR
• Record the dose
• Remember, it doesnt really matter what dose you
  start with (I.e., it doesnt have to be zero)

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Civil Defense Dosimeters

• Measure the total dose received (not dose rate)
• Sometimes called PICs
• The CDV-138 (Range 0-200 mR) is useful
• To use, simply record the dose at the beginning,
  end, and half-hour intervals
• Susceptible to false readings from mechanical
  shock (dropping it on the floor)
• Record all doses

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Dositec Mod. L36 Dosimeters
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Dositec Mod. L36 Dosimeters

• Measures total dose from 0 to 999 R with
  increments of 0.1 mR
• Measures the dose rate with a range of 0 to 100
  R/h in increments of 1 mR/h
• Auto ranging
• Uses one AA size battery with a life of 500 hours
• The display will cycle between dose and dose rate
• Clip on the dosimeter ensuring that the cli side
  is next to the body. Whenever possible, the
  dosimeter should be placed on the truck of the
  body where it will receive the highest dose.

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Direct Reading Dosimeter

• Delicate, do not drop. Leakage
• Instant reading, gamma dose
• Low range 0 - 200 or 500 mrem
• High range 0 - 5 rem
• Emergency range 0 - 50 rem

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Electronic Personal Dosimeter

• Detect photons
• Clips to belt/pocket
• Delicate
• Cold sensitive
• Direct reading,
• Dose History
• Downloadable

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EPD, continued

• Expensive, delicate, do not drop
• Sensitive to electromagnetic interference.
• Measures gamma and skin dose
• Dose and dose rate alarm levels can be set.
• You must record data

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Neutron Meter

• BF3 with polyethylene moderator
• Thermal to 10MeV
• 1mSv/hr - 100 mSv /hr
• Needs careful calibration

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Neutron Dosimeter
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Personal Air Sampler

• Small
• Worn in breathing zone
• Estimate inhalation

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Extremity Dosimeter

• Small TLD chip
• Very useful when needed

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Routine Dosimeter Use and Storage

• Wearing
• TLD badges and DCDs worn together
• Front of body at chest or waist level
• Outside clothing (exception some EPDs in cold
  weather)
• Within 15 cm of each other
• Position is critical dose calculations based on
  phantoms
• Head/Chest dosimeters

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Routine Dosimeter Use and Storage

• Storage when not in use
• Approved storage rack
• Not in lockers/desks/purses
• May be removed for changing/showering

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Chemical Dosimetry

• Absorption of energy produces chemical change
• Fricke
• Most well known
• Ferrous sulfate converted to ferric sulfate
• 0.001 M FeSo4 or Fe(NH4)2 (SO4)2 and 0.8 N H2SO4
• With time FeSo4 ? Fe(SO4 )3

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Fricke Dosimeter, Contd

• Interpret results with G value
• Radiation chemical yield
• (Molecules of product)/(100 eV of energy
  absorbed)
• Measure light absorption in solution, calculate
  concentration of product
• This is an absolute dosimeter

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Fricke Disadvantages

• Contamination prone
• Limited shelf life
• Limited range of usability

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Film As a Dosimeter

• Large dose range
• Millirad to Megarad dose range
• Microseconds to months of exposure
• Particle identification

Emulsion of Gelatin with AgX
Cellulose or Glass plate
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Film, continued

• Ionizing radiation interactions
• AgBr?AgBr -
• Forms a latent image
• Developing fixes Ag
• Reduces to metallic Ag and others around it
• Unreacted AgBr removed
• Opaque Ag left behind (the negative)
• Optically detect image

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Film As a Dosimeter
Unfiltered energy response
100
Log Relative Response, R
10
Filtered response
1
10
100
1000
Photon Energy, Eh?
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Reading Film Optical Density
Film A
Film C
Film Y
Optical Density
Film contrast is defined as d(OD) /dlogX
Log X (exposure)
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Using Film Key Issues

• Issues
• Sensitivity
• Reciprocity response constant over different
  exposure rates)
• Ability to generate a characteristic curve

Saturation
2
Linear response range
Optical Density
Flat response, OD independent of X due to fogging
0.4
Log X (exposure)