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.
- 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
Alpha Radiation Survey Meter
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)
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
- 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
- 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
- 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
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Multimedia
- Basic radiation principles (HHS/CDC)
- Screening people for external contamination, use of radation survey equipment (HHS/CDC)
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Selected References
- What is a Geiger counter? (The Vega Science Trust Videos)
- How to Perform a Survey for Radiation Contamination
- How to Detect Radiation: instruments and survey technique (REAC/TS)
- Video: Screening People for External Contamination: How to Use Hand-held Radiation Survey Equipment (HHS/CDC)
- Use of portable survey meters for initial screening and triage of internally contaminated people (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)
- Use of Radiation Detection, Measuring, and Imaging Instruments to Assess Internal Contamination from Inhaled Radionuclides (HHS/CDC)
- 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.
- 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)
- Population Monitoring in Radiation Emergencies: A Guide for State and Local Public Health Planners (PDF - 3.66 MB) (HHS/CDC, August 2007)
- How can you detect radiation? (Health Physics Society)
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