Contact Health Physics at the following numbers:

Main Health Physics phone (campus hours):   (303) 492-6523
CU-Boulder Environmental Health & Safety:  (303) 492-6025
CU-Boulder Police Dispatch (emergencies or after campus hours): 911 or (303) 492-6666
Health Physics FAX:  (303) 492-1322
Health Physics electronic mail: hpl@spot.colorado.edu

X-ray machine use at CU

X-ray machines have many uses on the three campuses of the University of Colorado. Primarily, these machines are used for various research purposes on non-human subjects. There are a few machines, however, used for medical purposes. Medical use of X-ray machines requires additional and more specific training than is provided in this packet. This packet is designed to inform you of certain radiation safety requirements and University policies regarding the safe use of X-ray machines. You should work with your professor to learn experimental protocols and procedures for use with your specific device.

Analytical X-ray machines

Analytical X-ray systems and equipment are groups of components utilizing X-ray or gamma radiation to determine the elemental composition or examine the microstructure of materials using diffraction or fluorescence analysis. Analytical X-ray devices are regulated under Part 8 of the Rules and Regulations Pertaining to Radiation Control issued by the State of Colorado. Analytical devices are inspected biennially (every two years) by a State Qualified Inspector.

Medical (human use) X-ray machines

Medical X-ray devices (healing arts or veterinary medicine) are regulated under Part 6 of the Rules and Regulations Pertaining to Radiation Control issued by the State of Colorado. Anyone planning to use a medical X-ray for human use must be separately licensed by the State of Colorado Medical Licensing Board. Medical devices are inspected annually by a State Qualified Inspector.

Authorized users of X-ray machines

All owners (a.k.a. "Authorized User," "Principal Investigator," or "P.I.") of radiation machines on campus are licensed by a group of representatives from the major campus departments using radiation called the "Radiation Safety Committee." The Radiation Safety Committee meets quarterly to review campus license applications for new licenses, license amendments and to review records of the radiation safety program. Once the license is approved, the owner of the machine, or "Licensee," is then responsible for making sure all safety protocols are observed while the machine is in use.

Health Physics must be notified in advance of intent to purchase, sell, move, give or receive an X-ray machine as a gift. This advance notice allows Health Physics an opportunity to address any radiation safety problems and to insure that the machine is properly registered with the State of Colorado Department of Public Health and Environment (CDPHE). State regulations require that each X-ray machine be inspected by a State Qualified Inspector every two years.

Radiation Safety Committee and Licensing procedures

All X-ray machines at the University of Colorado (Boulder, Denver, or Colorado Springs campuses) must be registered and periodically inspected according to state regulations. The safe use of X-ray machines at the University of Colorado falls under the purview of the CU Radiation Safety Committee and the Radiation Safety Officer (RSO). The RSO is a member of the Health Physics group of the Department of Public Safety, Division of Environmental Health & Safety. A license to use an X-ray machine (whether the machine is existing, new, or a gift) may be obtained by contacting the RSO at (303) 492-6523.

Minimum qualifications to receive a license to use X-ray machines include:

Work with the X-ray machine may not begin until the application receives approval from the Radiation Safety Committee. Upon approval of the application, a University of Colorado X-ray Machine License will be issued to the applicant. The license will authorize the possession and use of certain radiation machines. The license will also designate the campus building and room(s) where the work is to be carried out.

If the nature of the research changes from that specified on the license, an application for amendment must be submitted to the Radiation Safety Committee (an amendment application is available by contacting the RSO).

An X-ray machine Licensee is responsible for:

The safe use of X-ray machines

Radiation exposures from X-ray diffraction or fluorescence machines can be extremely hazardous. A dose of 300 rads can cause an erythema burn to the skin (erythema is a redding of the skin that looks like a sunburn). Dose rates in the primary beam of an X-ray machine can exceed 100,000 rads/minute. Any part of the body momentarily placed in the beam would receive enough radiation to cause serious radiation burns.

High Voltage Hazards

In addition to the radiation hazards, the high voltage power supply of X-ray machines can be particularly hazardous. Personnel must never tamper with high voltage equipment. Only properly trained personnel are permitted to install, repair or modify high voltage equipment.

Operators of X-ray machines

Personnel planning to use X-ray machines at the University of Colorado are required to successfully complete training through Health Physics prior to beginning work with any X-ray machine. Re-training is required every three years to continue using X-ray machines at the University of Colorado.

Only projects approved by the Radiation Safety Committee may be performed using an X-ray machine at the University of Colorado.

The Licensee is responsible for all operations associated with X-ray machines for which they are licensed, including radiation safety. These include, but are not limited to, the following items:

Operating Procedures

Operating procedures must be in writing and readily available to each person likely to use the machine. A copy of these procedures should also be provided to Health Physics.

The operator should be in immediate attendance at all times when the machine is in operation. When not in operation, the machine must be secured in such a way as to be inoperable to unauthorized persons.

Radiation Exposures

Radiation exposures to individuals must be so controlled that the maximum permissible dose limits are not exceeded. In particular, personnel must not expose any part of their bodies to the primary beam.

Equipment Requirements

Each X-ray unit must have a safety device which prevents the entry of any portion of an individual’s body into the primary X-ray beam path, or which causes the beam to be shut off upon entry into its path. This is also known as an "interlock."

Any unused ports must be secured in the closed position, in a manner preventing casual opening. Any X-ray unit installed after October 1, 1978 should be equipped with a shutter for each port on the radiation source housing that cannot be opened unless a collimator or a coupling has been connected to the port. Each source housing shall be equipped with an interlock that shuts off the tube if it is removed from the radiation source housing, or if the housing is disassembled.

All safety devices – interlocks, shields, shutters, warning lights, etc. – should be tested periodically (at least once a year) by the user to ensure their proper operation. Records of such tests should be recorded in the Radiation Survey Log. New logs are available from Health Physics.

Visual warnings

Visual warnings must be used to indicate the potential for radiation exposure on all devices of open beam configuration. Easily visible flashing lights or equally conspicuous signals located near the tube housing that indicate when the X-ray tube is "on" or "off" must be provided if the primary beam is controlled in this manner.

If the beam is controlled by shutters, a readily discernible indication of shutter status (open or closed) must be located near each port on the radiation source housing. Any equipment installed after October 1, 1978 must have fail-safe characteristics in the warning devices and these must be labeled so that their purpose is easily identified. A red warning light with the notation "X-RAY ON" or the equivalent, should be located on the control panel, and should light only when the X-ray tube is activated.

A sign or label bearing the words "CAUTION - RADIATION, THIS EQUIPMENT PRODUCES X-RADIATION WHEN ENERGIZED" or words having similar intent, must be placed near any switch which energizes an X-ray tube. A label bearing the radiation symbol and the words "CAUTION - HIGH INTENSITY X-RAY BEAM" must be placed on or adjacent to each X-ray tube housing. It should be located so as to be clearly visible to any person who may be working near the primary radiation beam. Each area or room containing analytical X-ray equipment must be posted with a sign bearing the radiation symbol and the words "CAUTION - X-RAY EQUIPMENT." Signs are available from Health Physics.

Modification/repair of the machine

Only properly trained personnel are permitted to install, repair, or make other than routine modifications to the X-ray generating apparatus and tube housing. The Radiation Safety Officer should be notified of any modifications made to the machine, as state regulations require that certain modifications and repairs trigger a re-inspection of the device before use may resume. Modifications to the safety interlocks require the prior, written approval of the Radiation Safety Officer.

Beam Alignment

Procedures and apparatus utilized in beam alignment should be designed to minimize radiation exposure to the operator. Particular attention should be given to viewing devices to assure that lenses and other transparent components attenuate the radiation beam to minimal levels. When alignment involves working near the open primary X-ray beam, the beam current should be reduced in order to lower exposure rates. If a fluorescent alignment tool is used, dimming the room light will permit a significant reduction in beam current. The fluorescent alignment tool should be long enough to permit the operator's hand to be kept a safe distance from the beam. The operator should be familiar with the manufacturer's recommended alignment procedures, and copies of these should be available for reference.

Each person performing beam alignments requiring work near the primary beam should be issued and wear an extremity dosimeter (TLD ring) by Health Physics (see section on Dose and Exposure Control). Contact Health Physics if you need a TLD ring.

Bypassing Safety Devices

If, for any reason, it is necessary to alter safety devices, such as bypassing interlocks or removing shielding, such actions must be:

Any attempt to bypass or alter safety devices should be undertaken only as the very last option in order to proceed with the research.

During the bypass period, a readily discernible sign bearing the words "Safety Device Not Working" must be placed on the radiation source housing.

Area Monitoring Requirements

Users should monitor routinely for stray or scattered radiation in the immediate vicinity of the X-ray machine with an appropriate detector. Contact Health Physics regarding an instrument for this use. This survey should be performed with the machine "on," in order to determine if there is leakage of X-rays. The results of the survey should be noted in a log and maintained in an easily accessible location for review by inspectors.

This survey should be performed:

Leakage radiation from the tube housing must be less than 2 mR/hr at 5 cm and leakage from the generator cabinet must be less than 0.25 mR/hr at 5 cm. All safety devices (interlocks, shields, shutters, shields, cabinets, etc.) should also be checked at the time of the survey.

Radiation protection surveys will also be conducted by the State Qualified Inspector every two years or by Health Physics upon request. Surveys by the Qualified Inspector or Health Physics are supplemental to the required surveys performed by the users.

Dose and Exposure Control

Personnel Monitoring

Operators of X-ray diffraction machines must wear a personnel dose-monitoring device, or dosimeter, whenever operating or working near an operating machine. The whole-body monitor should be worn on the front of the torso between the neck and the waist. The finger ring (if issued) should be worn on the hand most likely to be exposed. The dosimeters used at the University of Colorado do not give an immediate response to radiation exposure. Rather, dosimeters are a tool to provide a record of personnel radiation exposure and identify possible problem areas on a continuing basis.

Radiation Exposure

All recommendations as to permissible radiation exposures should be interpreted assuming that any radiation exposure, except as required by medical necessity, is undesirable. There is a certain amount of unavoidable natural background radiation present in our environment. The philosophy of radiation safety, based on present knowledge and assumptions, is to reduce all radiation exposures above background to a level "As Low As Reasonably Achievable" (ALARA). The maximum permissible exposures given below are to be used only as general guides. It should not be considered that these are tolerable exposures, but rather represent the upper limits which should be reached only infrequently, if ever.

Radiation Exposure Limits

Federal and State regulatory agencies have set the following limits for maximum permissible external & internal radiation exposures for occupationally exposed individuals ("radiation workers"):

Area Affected Annual Dose (in the unit rem)
Whole body (internal + external exposure) 5
Lens of the Eye 15
Skin or Extremity 50
Individual Organ or Tissue 50
Dose to an embryo/fetus (during the pregnancy) 0.5

For the more restrictive dose limitations to an embryo/fetus to be in effect, the pregnant woman is encouraged to voluntarily inform Health Physics, in writing, of her pregnancy and the estimated date of conception. If you are pregnant and would like more information on this area of the regulations, please contact Health Physics.

The permissible limits for persons under 18 years of age are 10% of the above limits. The total effective dose equivalent to individual members of the "general public," from operations at the University, must not exceed 0.1 rem per year.

Emergency Procedures

In the event of an over-exposure or emergency involving ionizing radiation, notify Health Physics at (303) 492-6523 as soon as possible. If the emergency is life threatening (serious injuries, fire, explosions, gas leak, etc.) call 911. CU-Boulder Police can contact Health Physics and other emergency services (Fire Department, ambulance, etc.) as needed. After hours, the Health Physics staff may be contacted through the CU-Boulder Police by dialing 911 (or (303) 492-6666). Each laboratory should have emergency procedures clearly posted in an easily accessible location.

If you are using X-ray machines on the Denver campus (UCD), you should use the following emergency numbers:

CU-Boulder Health Physics (campus hours): (303) 492-6523

Auraria/UCD Police Dept. (after campus hours): 911 or (303) 556-3271

If you are using X-ray machines on the Colorado Springs campus (UCCS), you should use the following emergency numbers:

CU-Boulder Health Physics (campus hours): (303) 492-6523

UCCS Public Safety (after campus hours): (719) 262-3111

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Forward to the X-ray User's Quiz!