The rules in this section apply to the following miscellaneous X-ray producing equipment: electron microscopes, ESCA spectrometers, electron microphones, luminoscopes, and cold-cathode gas discharge tubes. These provisions do not apply to television receivers or video display terminals. These requirements are in conformity with NC DRP regulations.
Posting: No area posting is required for miscellaneous X-ray equipment.
Warnings and labels: A clearly legible and visible label bearing the statement: "CAUTION: THIS EQUIPMENT PRODUCES X-RAYS INCIDENTAL TO ITS PRIMARY FUNCTION - TO BE OPERATED BY QUALIFIED PERSONNEL ONLY" must be posted on all miscellaneous X-ray producing equipment.
In addition to the above requirement, cold-cathode gas discharge tubes must bear the following labels:
Radiation Limits
Radiation emitted from electron microscopes, electron microprobes, ESCA spectrometer, and luminoscopes must not exceed an exposure rate of 0.5 mrem/hr at any accessable location on the external surface.
Radiation exposure from cold-cathode gas discharge tubes must not exceed 10 mrem/hr at 30 cm from the external surface averaged over 100 square centimeters.
All miscellaneous X-ray producing equipment must contain sufficient shielding, and be located and operated so exposure rates in unrestricted areas do not exceed 2 mrem/hr, or 100 mrem/yr.
Personnel Monitoring: Personnel monitoring is not required for users of miscellaneous X-ray producing equipment.
Potential X-ray Exposure From Magnetic-Effect Tubes
Magnetic-effect tubes demonstrate that cathode rays carry an electrical charge that can be deflected by a magnetic field. These tubes may produce X-rays incidental to their intended use and should be used with caution. Where there is a source of electrons, a target, sufficiently high voltage, and tube gas pressure within the proper range, X-ray production will occur. X-ray output from magnetic-effect tubes, however, is unpredictable and intermittent. Under identical operating conditions it may vary from one tube to another; one tube may be an X-ray producer while another may not. X-ray production may vary during a given period of operation or from day to day for the same tube.
Since the educational benefits derived from these tubes are gained by visual observation of their operation, unshielded operation of these tubes is required; with the subsequent potential for student and operator exposure. To keep exposures to a minimum, requirements for the safe use of these tubes are as follows:
- Magnetic-effect tubes must be used only for demonstrations conducted by the instructor.
- The instructor should stand as far as practical from the tube during the demonstration.
- Only the instructor must operate a magnetic-effect tube.
- Bystanders should stand at least 8 feet from an operating tube.
- Tubes must always be operated with the correct polarity and the lowest practical current and voltage.
- Operating time is to be kept to a minimum.
Radiation Safety Surveys
Radiation surveys must be performed and documented by the Radiation Safety Division upon installation and following any maintenance or tube replacement.
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Terms and Definitions |
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Access panel |
A panel designed to be opened for maintenance purposes to permit access to the interior of the cabinet. |
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Aluminum equivalent |
The thickness of type 1100 aluminum alloy affording the same attenuation as the material in question. |
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Analytical X-ray equipment |
Equipment used for X-ray diffraction and fluorescence analysis (excludes cabinet X-ray systems, electron microscopes and diagnostic X-ray equipment). |
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Automatic exposure control |
A device that automatically controls one or more technique factors in order to obtain a required quantity of radiation. |
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Beam-limiting device |
A device that provides a means to restrict the dimensions of the X-ray field. |
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Cabinet X-ray system |
X-ray system with the X-ray tube installed in an enclosure, which is intended to contain the object being irradiated, provide radiation attenuation, and exclude personnel from its interior during X-ray generation. |
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Certified components |
Parts of X-ray systems that are subject to regulations adopted under the Radiation Control for Health & Safety act of 1968 |
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Cooling curve |
The graphical relationship between heat units stored and cooling time. |
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Dead-man switch |
A switch that can only be keptON by continuous pressure. |
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Diagnostic X-ray system |
An X-ray system designed for irradiation of a human or animal for the purpose of diagnosis or visualization. |
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Diffracted beam |
A beam composed of mutually reinforcing scattered X-rays. |
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Direct scattered radiation |
Scattered radiation that has been deviated in direction only by the object exposed to the useful beam. |
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Enclosed beam configuration |
An analytical X-ray system in which all possible X-ray paths are fully enclosed. |
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Fail-Safe design |
A design feature that guarantees that the beam port shutters close or prevent appearance of the primary beam in the event of failure of a safety or warning device. |
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Gonad shield |
A protective barrier for the testes or ovaries. |
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Half-value layer |
The thickness of a material that attenuates the beam of radiation to one-half of its original value. |
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Healing arts screening |
The testing of humans using X-ray equipment for the detection or evaluation of health problems, when such tests are not specifically and individually ordered by a medical doctor. |
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Heat unit |
A unit of energy equal to the product of the peak voltage, current, and seconds. |
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Image intensifier |
A device that converts an X-ray pattern into a corresponding light image of higher energy density. |
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Image receptor |
A device, such as a fluorescent screen or radiographic film, that transforms incident X-ray photons into a visible image. |
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Inherent filtration |
Filtration of the useful beam provided by the permanently installed parts of the tube housing. |
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Miscellaneous X-ray equipment |
Equipment that produces X-rays secondary to its primary function |
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Kilovolt peak (kVp) |
The maximum value of the potential difference across the X-ray tube during an exposure. |
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Lead equivalent |
The thickness of lead affording the same attenuation as the material in question. |
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Leakage radiation |
Radiation, except the useful beam, emanating from the tube housing. |
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Local components |
Includes areas that are struck by X-rays, such as radiation source housings, port and shutter assemblies, collimators, sample holders, cameras, goniometers, detectors and shielding; but not including power supplies, transformers, amplifiers, readout devices and control panels. |
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Milliampere second (mAs): |
The product of tube current and exposure time. |
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Mobile equipment |
X-ray equipment mounted on a permanent base with wheels. |
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Open-beam configuration |
An analytical X-ray system in which some part of the body could accidentally be placed in the primary or diffracted beam path. |
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Primary beam |
X-rays that pass through an aperture of the source housing by a direct path from the X-ray tube. |
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Protective apron |
An apron made of radiation-attenuating materials. |
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Protective barrier |
A barrier of radiation-attenuating materials used to reduce radiation exposure. The types of protective barriers are:
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Qualified expert |
An individual, who has demonstrated by training and experience to the satisfaction of the State, that he/she possesses the knowledge and training to measure ionizing radiation, to evaluate safety techniques, and to advise others regarding radiation safety needs. |
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Safety interlock |
Device that is intended to prevent the generation of X-rays when a door or access panel is opened. |
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Scattered radiation |
Radiation that has been deviated in its direction during passage through an object. . |
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Stationary equipment |
X-ray equipment that is installed in a fixed position |
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Technique factors |
The condition of operation that is the peak tube potential in kV and either the tube current in mA and exposure time in seconds, or the product of the tube current and exposure time in mAs. |
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Tube rating chart |
The set of curves that specify the rated limits of operation of the tube in terms of the technique factors. |
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Useful beam |
Radiation that passes through the tube housing port and the aperture of the beam-limiting device when the exposure switch is activated. |
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Variable aperture |
A beam-limiting device that allows for stepless adjustment of the X-ray field. |
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X-ray source housing |
That portion of an analytical X-ray system that contains the X-ray tube. |
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