Radiation Detection and Survey Devices

Key Radiation Detection Device Monographs and Articles

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Nuclear & Electronics Product Page

Introduction and Basic Information

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Review of Radiation Dosimeters Types for Dose Monitoring, Worker Safety, and Environmental Monitoring

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Selection of Radiation Detection Devices by Radiation Incident Response Zone

Table 2. Comparison of Radiation Devices by Preferred Response Zone

Source: Radiation Dosimeters for Response And Recovery, Market Survey Report (PDF - 1.87 MB) (DHS/OSTP/NUSTL, June 2016, page 9)

• This graphic shows that no one device is appropriate for every situation.
• The x-axis on the bottom of the table above is exposure rate (R/h)
• The x-axis on the top corresponds to Response Zones (Cold, Hot, Dangerous-Radiation) and denotes where each dosimeter type might be most useful. Definition of response zones is shown on the graphic, but various groups have defined the zones differently.
• The y-axis on the left of the graphic lists types of dosimeters that are appropriate for the assigned rose rate work area
• In the source document for this table, the many categories of dosimeters are mentioned with many individual products listed for each type.

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More about Selected Examples of Detection Devices

Geiger Mueller (GM) Detectors with Pancake Probes

• What is a Geiger counter? (The Vega Science Trust Videos)
  • Detects and measures radiation in the environment in real time
• How to survey for external contamination
• How to Use Hand-held Radiation Survey Equipment (Part 1) (YouTube - 19:02 minutes) (HHS/CDC)
• G-M Detectors Job Aid - Use a Geiger-Muller survey meter to check for contamination. One page pamphlet. (PDF - 429 KB) (HHS/CDC)
• What is a "count" of radiation? A “count” is not a unit of radiation but rather a defined (unitized) response capacity of a device to an energy domain and dose rate. The count rate is affected by attenuating material between the dectector and the source and the source energy spectrum.

  
  

  • Radiation energy detected by some devices is registered as a "count."
  • Devices detect only a percent of the total energy (radioactive decays or disintegrations) released by radioactive material. This is the solid angle of the source point to the detector vs 4π spherical domain from the point source.
    • Efficiency: the percentage of the total radiation energy released that is detected by a device
  • Appropriate "efficiency" conversion factors can be used to
    • Determine the actual number of disintegrations per second or minute (DPS or DPM); requires a standard reference source
    • Actual disintegrations per unit of time are measured in units of curies or becquerels
  • Example
    • [CPM] divided by [efficiency] equals DPM
    • Example: 100 CPM at 20% efficiency = 100/0.2 = 500 DPM
• See Selected References section below.

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Alpha Radiation Survey Meter

• Radiation survey meter with probe appropriate for detecting alpha radiation.
• Alpha Scintillation Detectors (Part 3) (YouTube - 3:54 minutes) (HHS/CDC)

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Dose Rate Meter

• This survey meter measures environmental levels of penetrating, ionizing radiation
  • May be used to determine whether it is safe to enter an area and, if so, for how long
  • Provide readings in units of roentgens per unit time (e.g., mR/hr)

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Personal Dosimeters

• What is a personal dosimeter?
  • A small radiation monitoring device worn by persons entering environments that may contain radiation
  • See historical collection of personal dosimeters (ORISE)
• Who should wear a personal dosimeter?
  • Healthcare or laboratory workers in non-emergency environments that may contain protected (contained/or open) radiation sources (lead “pig”) or open source exposure fields (Cs-137 and Co-60) sources, for example.
    • Examples: radiology, nuclear medicine, and radiation oncology department staff
  • Workers in emergency environments that may contain radiation
    • Examples: first responders and first receivers
  • Workers in industrial environments where radiation is used
    • Examples: nuclear power plant workers or employees at radiation sterilizing facilities, nuclear medicine facilities, etc.
• Where are personal dosimeters usually worn?
  • Flat badges are usually worn on the torso, at the collar or chest level, but can be worn on the belt, or forearm
  • Ring shaped badges can be worn on the finger when dose to the finger may exceed dose to the badge worn elsewhere on the body, i.e. material handling and source operations or transfers.
  • First responders and first receivers
    • Wear water-resistant personal dosimeters on the outer layer of personal protective equipment (PPE).
    • Should be able to easily see and hear a dosimeter alarm while wearing PPE
    • May wear a personal dosimeter underneath waterproof outerwear
• CAVEATS:
  • Radiation exposure in the environment may not be uniform.
    • Dose registered by a badge worn on the torso may not be the same as dose received elsewhere on the body.
    • When working close to radiation sources (e.g., removing radioactive shrapnel), the hands/fingers may receive a higher dose than the torso, and should be monitored by a personal dosimeter on the finger.
  • Real time readings from personal dosimeters are not available from all devices.
  • Emergency responders may require self-reading devices that provide dose information in real time.
• Types of personal dosimeters
  • See REMM table which reviews many types of personal dosimeters
  • Non-self reading dosimeters: real time dose information not available
    • Film badges
      • Contain filters and film which identify and quantify the type of radiation (e.g., x-rays, gamma, beta, neutron)
      • Least accurate personal dosimeter for recording very low exposure (e.g., below about 10 mR)
      • Sensitive to temperature and humidity, which may limit use by emergency responders
      • Available for use on torso and finger
      • See historical collection of personal dosimeters (ORISE)
    • Thermoluminescent dosimeters (TLDs)
      • More sensitive than film badges
      • Some can measure readings lower (more sensitive) than film badges. Film badges can saturate to no longer respond to added doses; films reach maxima asymptotically – use the most linear response domain to limit the dose maxima
      • Use lithium fluoride crystals to record radiation exposure
      • Not sensitive to heat and humidity
      • Available for use on torso and finger
      
      
      
      
    • Optically stimulated luminescence (OSL) dosimeter
      • More recent device of choice for occupational exposure monitoring
      • More sensitive than film badge or TLD
      • Use aluminum oxide to record radiation
      • Results can be read up to a year following exposure
      • Available for use on torso and finger
      
      
      
      
      
  • Self-reading dosimeters (aka. direct-reading dosimeters, self-reading pocket dosimeters, pocket electroscopes): provide real time dose information
    • Older types: See historical collection of personal dosimeters (ORISE)
      • Dose is determined by looking through the eyepiece on one end of the dosimeter, pointing the other end towards a light source, and noting the position of the fiber on a scale

      
      

    • Newer types
      • Electronic
      • Some can measure and display dose rate and total dose
      • Some can alert wearer that pre-set dose rate and/or total dose limits have been exceeded by both visual and vibrating alarms
      • Dose rate and total dose readings can be downloaded in real time to a computer
      • Some are designed for use in extreme environments by emergency responders wearing bunker gear or higher-level PPE (See examples below)
      
      
      
      
      
      
      
      

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Portal Monitors

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Multimedia Training about Radiation Detection Devices

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Selected References

Disclaimer:
Reference on this page to any specific commercial product, process, service, manufacturer, or company does not constitute its endorsement or recommendation by the U.S. government or the U.S. Department of Health and Human Services or any of its agencies. Products are displayed as examples only. HHS is not responsible for the contents of any "off-site" Web page referenced on this site.

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Detecting radiation is achieved through the use of a variety of instruments. The most common type of radiation detector is a Geiger-Mueller (GM) tube, also called a Geiger counter.

How to use a Geiger-Mueller (GM) counter to detect radiation

Get the GM counter and batteries from storage; prepare the instrument and determine background level.

Preparing the meter:

• Position the Geiger counter with the meter away from you. Locate and open the battery compartment.
• Put the batteries in the meter using proper orientation (up/down).
• Close and latch the battery compartment.
• Check the batteries using the "range" switch or "bat" button; the method depends on the type of instrument. The meter needle should move to area on scale marked battery, indicating the batteries are good. If the battery check fails, replace the batteries with a fresh set and repeat the battery check.
• Turn the "F/S" switch to "S" (slow). Some instruments may have a picture of a hare and a tortoise to represent fast and slow.
• Generally, the fast setting is used to detect radioactivity, and the slow setting is used to obtain counts. Turn the "audio" switch to "ON."

Measuring the background radiation:

• Check that the "F/S" switch is on "S" (slow).
• Move the range switch to the most sensitive position.
• Remove the probe cover if one is in place.
• Measure the background radiation for 60 seconds: write down the reading. Since background radiation varies with time, it may be desirable to make several counts and average the results. Record the reading.
• Readings may vary, but a range of 20-100 counts/min, or a reading of approximately 0.02 mR/hr (i.e. 0.2 on the 0.1 range setting), or 0.2 micro Sv/hr, is reasonably expected in normal circumstances.
• Record background reading.

How to survey a person

Using the instrument:

• Move the "F/S" switch to "F" (fast response).
• Set the instrument selector switch to the most sensitive range of the instrument.
• Holding the probe approximately 1/2 to 1 inch from the person’s skin, systematically move the probe across the entire body from head to toe on all sides. Try to maintain a consistent distance.
• Move the probe slowly (about 1 inch per second).
• To avoid contaminating the probe, do not let it touch the skin or clothing.
• Locate the point that produces the most clicks. (Turn the "F/S" switch to "S" to take a reading at this location. Remember to reset it to "F" before continuing survey.)
• If the meter reads off-scale, adjust the range of the instrument by moving the range selector switch and pushing the “reset” button.
• Document time and radiation measurements.
• In general, areas that register more than twice the previously determined background level are considered contaminated. If the accident circumstances indicate that an alpha emitter (such as plutonium) or low energy beta emitter could be a contaminant, a health physicist should always be consulted.
• Note that some GM instruments cannot detect alpha radiation and some low-energy beta radiation. Because alpha radiation is non-penetrating, it cannot be detected through even a thin film of water, blood, dirt, clothing, or through probe cover.

Ending the radiation survey:

• Switch off the meter.
• Replace the cap on the meter probe.
• Take the batteries out.
• Put the Geiger counter back in its case.

The following procedures are recommended for personnel monitoring:

• Have the person stand on a clean pad.
• Instruct the person to stand straight, feet spread slightly, arms extended with palms up and fingers straight out.
• Starting at the top of the head, cover the entire body, including the soles of the feet.
• Have the subject turn around, and repeat the survey on the back of the body.

This probe is used for the detection of alpha radiation.

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