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California State University, Fullerton

X-Ray Safetyknee xray

X-rays are a form of invisible, high-frequency electromagnetic radiation. They are produced by accelerating electrons at a metal target. X-rays are used in various medical and research applications. The following is basic safety information for x-ray use.  Detailed training is required on the specific x-ray equipment in use.


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General Considerations for X-Ray Use

Research and medicine uses many types of x-ray equipment including analytical, medical, dental, fluoroscopic, cabinet systems and electron microscopes. All radiation generating devices such as x-ray machines must be registered with the Radiation Safety Officer (RSO).  Training  is required to ensure that the user is aware of the hazards posed by the high radiation intensities of these beams. While these device produce a large amount of radiation in a small diameter beam, it is readily shielded and protected from causing human exposure.

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Analytical X-Rays

The predominant x-ray-producing equipment used in research is analytical x-ray. It produces intense beams of low-energy x-rays. Exposure to the direct beam can cause severe injury. To prevent exposures, newer instruments are designed with hood enclosures, interlocks and beam shielding to minimize the risk of inadvertent exposures. It is possible that the radiation exposure rate from the primary beam can be up to 40,000 Roentgen per minute. With this high exposure rate, the hazard is not limited to the primary beam, but can also be related to leakage or scatter radiation. As result, these x-ray machines should not be modified without the authorization of the RSO. A radiation survey should be done whenever a new sample is placed in the beam, the beam is diffracted, experimental setup changed or equipment is replaced. The analytical x-ray machines usually have a low energy that can be readily shielded with about 1 mm of lead. Due to the intensity of the primary beam, leakage and scatter may create a significant source of unwanted radiation. Use shutters and collimators, secure unused ports, reduce the beam cross-section by collimation, and whenever appropriate enclose the entire beam path or use a sufficient beam stop. Consider additional sources of x-rays from miscellaneous support equipment such as high-voltage supplies.

 

Dosimetry

All equipment operators are required to wear ring and whole body dosimeters. While equipment is designed to keep exposures to a minimum it is possible that unusual events such as the alignment for sample manipulation could lead to inadvertent exposures. These operations should never be attempted without appropriate safety precautions.

 

Training

All users must attend the Radiation Users Training Session and must also be provided specific written instructions by the Permit Holder before using the equipment. These instructions include notice of radiation hazards; machine specific safe work practices; and symptoms of acute, localized exposure to radiation.

 

Postings

The following document should be placed near the controls of each analytical x-ray unit and readily accessible to the operator:

  • Specific written instructions
  • Analytical x-ray Emergency Procedure
  • Symptoms of Injury from Acute Local Exposure to Radiation
  • Radiation Hazards from Analytical x-ray Units
  • Safe Working Practices for Analytical x-ray

 

Labels

Analytical x-ray equipment will be posted and labeled with:

  • A label bearing the words "Caution Radiation This Equipment Produces Radiation When Energized" near the tube activation switch.
  • A sign "Caution High-Intensity x-ray Beam," next to each tube-head. The sign must be clearly visible to any person operating, aligning, or adjusting the unit or handling or changing a sample.
  • A posting on the exterior side of the room's doors indicating the presence of x-ray producing equipment such that visitors to the lab will see the sign.

 

Indicators

All x-ray machines will contain an operational and clearly visible indicator of an active x-ray beam near the x-ray tube. In addition, there must be a shutter status indicator that unambiguously reports if the shutter is open or closed.

 

Interlocks and Safety Devices

Operational interlocks and safety devices will be provided to ensure that the primary x-ray beam can not be interrupted by any portion of an individual's body or extremities or by machine equipment under any operating condition. If the beam is interrupted, this interlock will shut off the primary beam. Interlocks and safety devices may not be altered without the written authorization of the RPO. Approved temporary modifications must be terminated as soon as possible, specified in writing and posted near the x-ray machine tube and operators console. Securely close any unused tube ports to prevent accidental opening.

 

Analytical x-ray Emergency Procedure

If there is a suspected or actual case of accidental radiation exposure, turnoff the system power and notify the RPO immediately. If required, exposed individuals should go to the University Health Services Urgent Care Clinic to seek medical attention.

Biological Effects of Acute X-Ray Exposure

With a properly functioning machine, there is little risk of radiation exposure. However, one should know the signs of an acute exposure to a localized area of the human body. These symptoms are shown in Table 1. Be aware that these effects can be caused by contact with the beam for only a fraction of a second. Typical primary beam exposures are 100,000 to 400,000 rad per minute. The most common effects from a large radiation exposure from an x-ray device is reddening of the skin (erythema). With a dose of a few hundred rem the superficial layers of the skin are damaged and the skin will redden in a fashion similar but more complex than a sunburn. The erythema effect will most often reverse itself within a few weeks. It is also possible that doses on this level could damage cell division and temporarily stops hair growth and possibly causes the hair to fall out. With a low enough dose, hair growth should return. There could also be damage to the sebaceous glands that produce the skin oil, which could cause a temporary decrease in the amount of oil produced. There are other less common and less transitory responses. If a large area is exposure to a large amount of radiation, there could be changes in the skin pigmentation. This effect may not be reversible and could result in permanent skin changes. If the exposure is large the transitory damage to the skin, skin hair, or sebaceous glands could cause skin scarring or lead to Radiation Dermatitis, Chronic Radiation Dermatitis, or radiation induced skin cancer. To protect yourself from the radiation consider the following potential sources of radiation exposure:

 

  1. The primary beam.
  2. Primary beam leakage from poor shielding or guide tube replacement.
  3. Beam penetration through stops and shutters.
  4. Secondary radiations from beam interaction of the primary beam with the sample or shielding.
  5. Radiation released from the diffraction of the beam.
  6. Radiation produced from support equipment such as power supplies.
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Electron Microscopes

General safety regulations for using electron microscopes.

  1. Only personnel trained and approved by the responsible Principal Investigator may operate an electron microscope.
  2. An operational fail-safe light is visible to the operator indicating when x-rays are being produced.
  3. Use interlocks, barriers or administrative controls to ensure no one can gain access to the primary beam or high scatter radiation areas.
  4. Use a calibrated thin-window GM survey meter to verify shielding effectiveness and monitor radiation levels.
  5. Secure electron microscopes against unauthorized use by using a unit key control or the room lock. Stop the primary beam by secured shielding that cannot be readily displaced.
  6. Secure unused ports to prevent accidental exposures.
  7. Maintain an operating log that includes the date, operator, beam voltage, and current time on and off (or total exposure time).
  8. Do not modify the built-in shielding and viewing ports. If modifications must be made, contact the Radiation Officer in Environmental Health and Safety for a safety survey of the unit.
  9. Notify the Radiation Safety Officer immediately in the event of any abnormal personnel radiation exposure.
  10. Changes in the location or disposition of electron microscopes must have the approval of the Radiation Safety Officer. Notify the RSO prior to the acquisition, disposal, or transfer of any electron microscope.
  11. Contact the RSO for information regarding radiation safety or radiation survey instrumentation. 

X-Ray Defraction

General Safety Regulations:

  1. Diffraction/fluorescence units may only be operated by Radiation Safety authorized personnel. All authorized personnel must receive instruction in and demonstrate an understanding of the operation of the machine before starting unsupervised work.
  2. An operational fail-safe light is visible to the operator indicating when x-rays are being produced.
  3. Use interlocks, barriers or administrative controls to ensure no one can gain access to the primary beam or high scatter radiation areas.
  4. Use a calibrated thin-window GM survey meter to verify shielding effectiveness and monitor radiation levels.
  5. If the machine is modified, obtain RSO authorization before using the equipment.
  6. Whole body and finger ring dosimetry is required for all personnel working with diffraction/fluorescence units.
  7. Do not use the safety interlock to turn the machine off; use the main switch.
  8. Do not override the safety interlock unless there is a Radiation Safety approved written procedure.
  9. Make sure the machine is OFF before changing samples or the primary tube safety shutter is closed and verify there is not active beam present; always check the current and voltage meters and/or use a survey meter to detect x-rays.
  10. Do not operate with removed covers, shielding materials, or tube housings; or with modified shutters, collimators or beam-stops. Verify that the tube is off and remains off until the machine is completely reassembled and any modifications have been approved. Use the main switch to shut the machine off; do not rely on the safety interlock.
  11. Check radiation scatter with a survey meter after each realignment. Notify the Radiation Safety Officer immediately if there are unusually high readings.
  12. Secure unused ports to prevent accidental exposures.Secure diffraction/fluorescence against unauthorized use by using a unit key control or the room lock. Stop the primary beam by secured shielding that cannot be readily displaced.
  13. Maintain an operating log that includes date, operator, beam voltage and current, and time on and off (or total exposure time) for each unit use.
  14. Notify the Radiation Safety Officer immediately if there is a real or perceived abnormal personnel radiation exposure.
  15. Obtain approval for any location changes, purchase or removal of diffraction/fluorescence units from the Radiation Safety Officer. Notify the RSO prior to the acquisition, disposal, or transfer of any diffraction/fluorescence unit.
  16. Contact the RSO for information regarding radiation safety or radiation survey instrumentation. 

X-Ray Cabinets

General Safety Regulations:

  1. Only individuals authorized on the permit may operate the machine. All authorized users must receive instruction in and demonstrate an understanding of the operation of the machine before starting unsupervised work.
  2. An operational fail-safe light is visible to the operator indicating when x-rays are being produced.
  3. Use interlocks, barriers or administrative controls to ensure no one can gain access to the primary beam or high scatter radiation areas.
  4. Use a calibrated thin-window GM survey meter to verify shielding effectiveness and monitor radiation levels.
  5. Whole body and finger ring dosimetry is required for all personnel working with cabinet units.
  6. Do not use the safety interlock to turn the machine off; use the main switch.
  7. Do not override the safety interlock unless there is a Radiation Safety Officer approved written procedure.
  8. Make sure the machine is OFF before changing samples or the primary tube safety shutter is closed and verify there is not active beam present; always check the current and voltage meters and/or use a survey meter to detect x-rays.
  9. Do not modify the built-in shielding. If modifications must be made, contact the RSO for approval to restart instrument.
  10. Secure unused ports, if any, to prevent accidental exposures.
  11. Secure cabinet units through a unit key control or room lock.
  12. Maintain an operating log that includes date, operator, beam voltage and current, and time on and off (or total exposure time) for each unit use.
  13. Notify the RSO immediately if there is a concern for or any abnormal personnel radiation exposure.
  14. Obtain approval for any location changes, purchase or removal of diffraction/fluorescence units by the RSO. Notify the RSO prior to the acquisition, disposal, or transfer of any diffraction/fluorescence unit.
  15. Contact the RSO for information regarding radiation safety or radiation survey instrumentation.
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