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Radiation Detection Devices


Introduction

  • What are radiation detection devices?
    • Instruments that can identify the presence of radiation
    • There are many types of radiation detection devices.
      • No single device can detect all kinds of radiation.
      • No one device is useful in all situations.
  • What can specific radiation detection devices detect and measure?
    • Specific types of radiation, (e.g., alpha, beta, gamma, neutron).
    • Specific levels (or ranges) of radiation energy (in kV, MV).
    • "Counts" per unit time (minute or second)
    • Roentgens (R) per unit time (e.g., milliRoentgen per hour [mR/hr])
    • Accumulated dose (in units of gray or rad)
    • Current dose rate (in units of gray or rad per unit time)
  • Do all radiation detection devices provide radiation information in real time?
    • Radiation survey meters (e.g., Geiger Muller and similar devices) detect radiation in real time
    • Personal dosimeters
      • Film badges do not provide information in real time, but they can detect prior radiation exposure if the device was worn at the time of exposure.
      • Self reading personal dosimeters can provide real time information about exposure
  • Who administers a radiation safety program including the use of personal dosimeters?
    • The radiation safety officer (RSO) will
      • Specify the types of survey meters and personal dosimeters required for given tasks
      • Supervise storage, maintenance and calibration of survey meters
      • Specify training and proper use of survey meters and personal dosimeters
      • Supervise proper issuance and collection of all equipment
      • Supervise reporting of dose registered on personal dosimeters
  • See Selected References section below.


Selected Examples

Geiger Mueller (GM) Detectors with Pancake Probes

    Pancake Geiger - Mueller detector 1
    Source: Steve Sugarman, REAC/TS

    Pancake Geiger - Mueller detector 2
    Source: Steve Sugarman, REAC/TS


  • What is a Geiger counter? (The Vega Science Trust Videos) Watch video
    • 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) Watch video
  • 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?

    G-M survey meter
    Source: Steve Sugarman, REAC/TS

    • 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.
      • 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)
      • 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.


Alpha Radiation Survey Meter



Dose Rate Meter

    Dose rate meter
    Source: Steve Sugarman, REAC/TS

  • 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)


Newer Radiation Detection Devices

  • Many are suitable for emergency responders
  • Multiple functions can be provided by one device
    • Identify isotopes
    • Measure dose
    • Measure dose rate
    • Alarm for pre-set conditions
    • Monitor several types of contamination: alpha, beta, gamma
  • Examples


Personal Dosimeters

  • What is a personal dosimeter?
  • Who should wear a personal dosimeter?
    • Healthcare or laboratory workers in non-emergency environments that may contain radiation
      Physician wearing a personal dosimeter
      • Examples: radiology, nuclear medicine, and radiation oncology department staff
    • Workers in emergency environments that may contain radiation
    • Workers in industrial environments where radiation is used
      • Examples: nuclear power plant workers or employees at radiation sterilizing facilities
  • 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
    • 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
    Finger ring dosimeter Finger ring dosimeter Finger ring dosimeter
  • 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
    • 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 than film badges
        • Use lithium fluoride crystals to record radiation exposure
        • Not sensitive to heat and humidity
        • Available for use on torso and finger
        Thermoluminescent dosimeters
        Thermoluminescent dosimeters
        Source: Hong Kong Observatory


      • 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

        Optically stimulated luminescence (OSL) dosimeter
        Optically stimulated luminescence (OSL) dosimeter
        Source: Harvard University, Environmental Health and Safety


    • Self-reading dosimeters (aka. direct-reading dosimeters, self-reading pocket dosimeters, pocket electroscopes): provide real time dose information
      • Older type
        • Often used in hospital settings
        • 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
        • See historical collection of personal dosimeters (ORISE)

        Personal dosimeters
        Self-reading dosimeters (top row: older types; bottom row: newer type)
        Source: Steve Sugarman, REAC/TS

      • Newer type
        • Electronic
        • 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)

        Micro-electronic Personal Dosimeter
        DOSE-GARD® Micro-Electronic
        Personal Dosimeter
        Source: Responder Knowledge Base (RKB), DHS/FEMA


        Ultra Radiac Plus Personal Radiation Monitor
        Ultra Radiac™-Plus Personal Radiation Monitor
        Source: Canberra



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Multimedia

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Selected References

  1. What is a Geiger counter? (The Vega Science Trust Videos) Watch video
  2. How to Perform a Survey for Radiation Contamination
  3. How to Detect Radiation: instruments and survey technique (REAC/TS)
  4. Video: Screening People for External Contamination: How to Use Hand-held Radiation Survey Equipment (HHS/CDC) Watch video
  5. Use of portable survey meters for initial screening and triage of internally contaminated people (HHS/CDC)
  6. G-M Detectors Job Aid - Use a Geiger-Muller survey meter to check for contamination. One page pamphlet. (PDF - 429 KB) (HHS/CDC)
  7. Use of Radiation Detection, Measuring, and Imaging Instruments to Assess Internal Contamination from Inhaled Radionuclides (HHS/CDC)
  8. Management of Persons Contaminated with Radionuclides: Handbook (NCRP Report 161, Volume I), National Council on Radiation Protection and Measurements, Bethesda, MD, 2008, Chapter 5: Performing Surveys and Controlling Personnel and Area Contamination.
  9. Handbook for Responding to a Radiological Dispersal Device, First Responder's Guide - the First 12 Hours (PDF - 4.26 MB) (Conference of Radiation Control Program Directors, Inc., September 2006)
  10. Population Monitoring in Radiation Emergencies: A Guide for State and Local Public Health Planners, Second Edition, April 2014. (PDF - 1.02 MB) (HHS/CDC)
  11. How can you detect radiation? (Health Physics Society)
  12. Use of Radiation Detection, Measuring, and Imaging Instruments to Assess Internal contamination from Intakes of Radionuclides (HHS/CDC)

Disclaimer:
Photos of examples of any radiation detection devices shown on any REMM pages are intended to be illustrative examples only. The picture does NOT constitute an official HHS endorsement or preference for that particular supplier's version of that item.

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